Quantum dots based antibacterial coating

Abstract

The present invention is directed to an antimicrobial substrate having a layer of PbTe quantum dots (QD) attached to an outer surface of the material. Further provided is a method of fabrication the substrate / modification of a material for obtaining an antimicrobial surface.

Description

QUANTUM DOTS BASED ANTIBACTERIAL COATINGCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 674,303 filed July 23, 2024, the contents of which are incorporated herein by reference in their entirety.FIELD OF THE INVENTION

[0002] The present invention, in some embodiments, relates to antimicrobial coatings and articles comprising same.BACKGROUND

[0003] Bacterial proliferation on surfaces, culminating in the development of colonies and subsequent biofilm formation, remains an ongoing and persistent problem in current times. Microbial colonization continues to pose great risk in human healthcare as well as in industries including food, marine and water systems, and in domestic settings, causing infection, fouling, corrosion, and a reduction in the cost efficiency of systems. This places materials with effective antibacterial properties in critical demand. Studies have shown that nanoparticles (NPs) effectively inhibit bacterial colonization and reduce biofilm development on surfaces. However, their application for antibacterial purposes is limited by toxicity and environmental concerns.

[0004] Various studies have examined the antibacterial activity of NPs and their composites, including Cu2SnSs, Ag, Au, ZnO, MgO. Quantum dots (QDs) including carbon and graphene dots have also been tested for their antibacterial properties. Even though these methods showed notable bactericidal effects, they may pose a considerable risk to human health in cases of in vivo biological applications or to the environment, as they can allow for easy accumulation of loosely held QDs within application sites or their release and dispersal over time to unintended locations, causing possible toxic effects to non-target organs in vivo or microbials in the environment.

[0005] Photovoltaic panels (PV) have been reported as susceptible to bacterial colonization, resulting in a decrease in their solar conversion efficiency. Accordingly, there is an unmet need for cheap and stable antimicrobial coatings on various surfaces such as glass, inter alia being suitable for application in the PV panels.

[0006] Lead Telluride (PbTe) is a narrow band gap semiconductor alloy that has been shown to possess excellent thermoelectric properties for various applications, including energy harvesting power generation, thermal sensing equipment, and solar cells.SUMMARY

[0007] The present invention, in some embodiments, is directed to an apparatus, a system comprising same, and methods of using same, for determining the presence of an analyte in a location.

[0008] According to a first aspect of the invention, there is provided a substrate comprising:• a material in contact with PbTe quantum dots (QD), wherein the QD are bound to an outer surface of the material,• wherein the QD are characterized by an average particle size in a range between 1 and 20 nm; and wherein the substrate is characterized by a bacterial loading below 10 colony forming units (CFU) per cm2.

[0009] In one embodiment, the QDs form a layer on top of the material; and the material is selected from glass, plastic and metal substrate.

[0010] In one embodiment, the substrate of the present invention wherein at least one of: (i) the QD are spherically shaped and are uniformly distributed within the layer; and (ii) wherein an average distance between adjacent QD within the layer is 0. l-10nm.

[0011] In one embodiment, the substrate of the present invention with the stoichiometric ratio of Pb in the substrate is between 48 % and 52 % as determined by EDS.

[0012] In one embodiment, the substrate, wherein the layer has an average thickness of between 3 nm and 1mm and is characterized by surface coverage of 70-100%.

[0013] In one embodiment, the substrate of the present invention, characterized by the mean contact angle of the PbTe layer is between 60 and 90 degrees.

[0014] In one embodiment, the substrate of the present invention, further comprising a ligand bound to the QD.

[0015] In one embodiment, the substrate of the present invention, wherein the ligand is an aromatic or aliphatic compound comprising one or more functional groups selected from thiol, amine, and carboxy, including any salt and any combination thereof.

[0016] In one embodiment, the substrate of the present invention, wherein the ligand comprises an amino phenyl, mercaptopropionic acid or both.

[0017] In one embodiment, the substrate of the present invention, wherein the amino phenyl is p-phenylene diamine (PDA).

[0018] In one embodiment, the substrate of the present invention has antibacterial activity, wherein the antibacterial activity comprises bactericidal and / or bacteriostatic activity.

[0019] In one embodiment, the substrate wherein the antibacterial activity comprises Gramnegative bacteria bactericidal and / or bacteriostatic activity.

[0020] In one embodiment, the substrate wherein the Gram-negative bacteria comprise E. coli, Salmonella Paratyphi B., or Pseudomonas aeruginosa, including any combination thereof.

[0021] In one embodiment, the substrate wherein the antibacterial activity is maintained after exposing said substrate to a temperature of at least 120 °C.

[0022] In one embodiment, the substrate wherein the antibacterial activity comprises anti- biofilm activity.

[0023] In another aspect, there is provided a method for preparing the substrate comprising:• applying a mixture comprising the QD on a surface of the material to obtain a coated material; and• drying the coated material, thereby obtaining the substrate.

[0024] In one embodiment, the method wherein the mixture is an aqueous dispersion; and wherein each of the QD is doped with a first ligand.

[0025] In one embodiment, the method wherein said applying comprises drop-casting, coating, spin coating, spray coating, flow coating, dip coating, extrusion coating, transfer coating, and printing, or any combination thereof; and wherein the first ligand comprises oleic acid.

[0026] In one embodiment, the method wherein a concentration of the QD in the mixture is between 1 and 100 mg / ml.

[0027] In one embodiment, the method further comprises a step of performing a ligand exchange by contacting the substrate with a second ligand, to obtain the QD doped with the second ligand.

[0028] In one embodiment, the method wherein the second ligand is an aromatic or aliphatic compound comprising one or more functional groups selected from thiol, amine, and carboxy, including any salt and any combination thereof.

[0029] In one embodiment, the second ligand is PDA.

[0030] In one embodiment, the material is selected from glass, plastic and metal substrate.

[0031] In one embodiment, the material is glass material, and the outer surface of the glass material facing the QD is coated with Indium tin oxide (ITO), or with Fluorine doped tin oxide.

[0032] In one embodiment, the ITO further comprises a TiO2 layer on top of the ITO, and wherein the TiO2 layer is in contact with the QD.

[0033] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0034] Further embodiments and the full scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.BRIEF DESCRIPTION OF THE FIGURES

[0035] Figs. 1A-1D include EDS, SEM image and size distribution of 6.1 nm PbTe quantum dots (QD) layer on TiO2 / ITO Glass. (1A) EDS spectrum, (IB) SEM image of the PbTe QD layer layer, (1C) Size distribution and (ID) SEM image of cubic QD.

[0036] Figs. 2A-2D are images showing antibacterial effect of 6.1 nm PbTe QD layers and blank controls on (2A) E. coli, (2B) S. Paratyphi B, (2C) P aeruginosa, and (2D) S. aureus with and without LE. LE= ligand exchange.

[0037] Figs. 3A-3C are bar graphs showing zone of inhibition (ZOI) of different sizes of PbTe QD layer with and without LE. (3A) 6.1 ± 0.5 nm, (3B) 9.8 ± 0.7 nm, and (3C) 13.2 ± 1.1 nm. LE= ligand exchange. Measurement errors associated with the zones of inhibition are ± 1mm to the nearest millimeter.

[0038] Figs 4A-4D are color maps based on the peak-to-peak height at 1540 cm'1to indicate the presence of S. Paratyphi B bacteria on (4A-4B) Blank control. (4C-4D) Substrate with a PbTe QD layer. Bluest regions represent minimum bacteria while reddest regions represent maximum bacteria with respect to each QD layer sample.

[0039] Figs 5A-5D. are FTIR spectra showing comparison of sample FTIR absorption spectra of bacteria on 6.1 nm PbTe QD-layered substrates to those on blank controls for (5 A) E. coli, (5B) S. Paratyphi B, (5C) P. aeruginosa, and (5D) S. aureus.

[0040] Fig. 6 is an FTIR spectrum of PbTe QDs (OA doped QD).DETAILED DESCRIPTION

[0041] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. Some features or elements described with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated.

[0042] In one aspect of the invention, there is provided a substrate comprising a material in contact with PbTe quantum dots (QD), wherein the QD are bound to an outer surface of the material, wherein the QD are characterized by an average particle size in a range between 1 and 20 nm; and wherein the substrate is (i) characterized by a bacterial loading below 10 colony forming units (CFU) per cm2; (ii) devoid of biofilm, or both (i) and (ii). In some embodiments, the substrate is as described herein, wherein the outer surface is devoid of biofilm. In some embodiments, the outer surface is characterized by antibacterial activity, as determined by zone of inhibition (ZOI) test.

[0043] In another aspect of the invention, there is provided a substrate comprising at least one surface, said at least one surface comprises a material in contact with PbTe quantum dots (QD); wherein the QD are characterized by an average particle size in a range between 1 and 20 nm; and wherein each of the QD comprises a plurality of ligands bound to the QD, wherein said bound is via a covalent bond, a non-covalent bond or via a coordinative bond; and wherein the plurality of ligands comprises a second ligand comprising an aromatic compound.

[0044] The terms “at least one surface” and “outer surface” are used herein interchangeably. In some embodiments, the QD are located or deposited on the at least one surface (which is the outer surface of the material, to distinguish from QD incorporated or embedded inside the material).

[0045] In some embodiments, the QD are characterized by an average particle size in a range between 1 and 20 nm, between 2 and 10 nm, between 2 and 8 nm, between 3 and 10 nm, between 2 and 15 nm, between 5 and 10 nm, between 5 and 8 nm, between 5 and 15 nm, between 3 and 15 nm, between 4 and 15 nm, between 5 and 15 nm, between 4 and 10 nm, between 1 and 10 nm, between 10 and 15 nm, between 11 and 15 nm, between 11 and 13 nm, between 11 and 14 nm, between 11 and 20 nm, between 10 and 17 nm, between about 6 and about 13 nm, or about 6nm, including any range between. The average particle size can be determined based on SEM image (e.g. number based average). Average particle size can be determined by processing the SEM image using a software, such Imaged.

[0046] In some embodiments, the QD are characterized by a particle size distribution of between 0.1 and 0.8, between 0.1 and 0.5, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8 including any range between. The size distribution can be determined based on SEM image using a software, such Imaged (e.g. number based).

[0047] In some embodiments, at least 50%, at least 70%, at least 80%, at least 90% of the QD within the layer are spherically shaped or semi -spherically shaped. In some embodiments, at least 50%, at least 70%, at least 80%, at least 90% of the QD within the layer are cubically shaped.

[0048] In some embodiments, at least at least 90% of the QD within the layer are spherically shaped or cubically shaped. In some embodiments, the QD are spherically shaped. In some embodiments, the QD are cubically shaped.

[0049] In some embodiments, the QD are characterized by an average particle size in a range between 1 and 10 nm, between 3 and 10, between 4 and 10, between 5 and 10 or between 6 and 10, including any range between and are spherically shaped.

[0050] In some embodiments, the QD are characterized by an average particle size in a range between 11 and 20 nm, between 11 and 18, between 11 and 16, between 11 and 15 or between 11 and 13, including any range between and are cubically shaped.

[0051] In some embodiments, the QD are crystalline as determined by X-ray spectroscopy (e.g. by XRD, the XRD pattern may comprise the following peaks at 20 angles: 23.8, 27.5, 39.4, 48.9, 56.9, 64.6, and 71.6, which correspond to

[0111] ,

[0200] ,

[0220] ,

[0222] ,

[0400] ,

[0420] , and

[0422] crystal planes of PbTe-OA QDs, based on available pattern in the database (PDF 01- 078-1904)) . In some embodiments, the QD are characterized by EDS spectrum, as presented in Figure 1A.

[0052] In some embodiments, the stoichiometric ratio of Pb in the QD is between 48 and 52 at.%, between 49 and 52 at.%, between 49 and 51at.%, or about 50at%., including any range between, as determined by EDS. In some embodiments, the stoichiometric ratio of Te in the QD is between 48 and 52 at.%, between 49 and 52 at.%, between 49 and 51 at.%, or about 50at%., including any range between, as determined by EDS.

[0053] In some embodiments, the QD further comprise a plurality of ligands bound thereto. In some embodiments, the QD are doped by the plurality of ligands. In some embodiments, the plurality of ligands is non-covalently attached to QD (e.g. adsorbed to the QD). In some embodiments, the plurality of ligands is covalently bound to QD. In some embodiments, the plurality of ligands forms a complex with QD (i.e. bound to the QD via a coordinative bond).

[0054] In some embodiments, each of the QD is bound to a plurality of ligands, wherein the plurality of ligands comprises a single species of ligands. In some embodiments, the plurality of ligands comprises distinct ligand species (e.g. two or more chemically distinct species).

[0055] In some embodiments, the ligand is an inorganic compound (e.g. a salt). In some embodiments, the ligand is a halide salt.

[0056] In some embodiments, ligand is an aromatic or aliphatic compound comprising one or more functional groups capable of binding the QD. In some embodiments, the ligand is a multi-functional (e.g. bi-, tri or tetra-functional) ligand. In some embodiments, the ligand comprises two or more functional groups. In some embodiments, each of the functional groupsis independently selected from thiol, amine, and carboxy, including any salt and any combination thereof.

[0057] In some embodiments, the plurality of ligands comprises a second ligand comprising an aromatic compound. In some embodiments, the plurality of ligands further comprises a first ligand comprising a fatty acid.

[0058] In some embodiments, the aromatic compound comprises an aromatic ring (i.e. an aromatic or a heteroaromatic, or a polycyclic ring comprises two or more rings selected from an aromatic, heteroaromatic ring or both and optionally further comprising a non-aromatic ring). In some embodiments, the aromatic ring is substituted by one or more functional groups selected from amine, alkyl-amine, thiol, alkyl- thiol, carboxy and alkyl-carboxy, including any salt and any combination thereof.

[0059] In some embodiments, the second ligand is selected from an amino phenyl, mercaptopropionic acid or both, including any salt thereof. In some embodiments, the second ligand is amino phenyl. In some embodiments, the amino phenyl comprises the aromatic ring substituted by amine, alkyl-amine, or both. In some embodiments, the amino phenyl comprises di-amino substituted phenyl. In some embodiments, the di-amino substituted phenyl is or comprises p-phenylene diamine (PDA).

[0060] In some embodiments, the first ligand is a C2-C30 fatty acid. In some embodiments, the C2-C30 fatty acid is between 2 and 30, between 5 and 30, between 10 and 30, between 5 and 20, between 5 and 15, between 10 and 30, between 10 and 20, between 15 and 20, between 12 and 20, between 5 and 20 carbon atoms long, including any range between. In some embodiments, the first ligand is oleic acid.

[0061] In some embodiments, the first ligand is a C2-C30 fatty acid and the second ligand is amino phenyl. In some embodiments, the first ligand is oleic acid and the second ligand is PDA.

[0062] In some embodiments, the plurality of ligands comprises the first and the second ligand, wherein a weight ratio between the second ligand and the first ligand is at least 2: 1, at least 3: 1, at least 5: 1, at least 10: 1, at least 20: 1 or between 1 : 1 and 100: 1, between 2: 1 and 100: 1, between 5: 1 and 100: 1, between 10: 1 and 100: 1, between 10: 1 and 1000: 1, including any range between.

[0063] In some embodiments, the QD are non-covalently bound or adsorbed to the at least one surface of the substrate. In some embodiments, the QD are non-covalently bound to an outer surface of the material.

[0064] In some embodiments, the QDs are distributed on the at least one surface in a form a layer. In some embodiments, the layer is located on top of the material / substrate. In some embodiments, the layer is bound to the outer surface of the material. In some embodiments, the layer is a coating on top of the material.

[0065] In some embodiments, the layer is a uniform layer. In some embodiments, the QDs are uniformly distributed within the layer. In some embodiments, the QDs are non-uniformly distributed within the layer. In some embodiments, the layer is a continuous layer. In some embodiments, the layer is a non-continuous layer. In some embodiments, the surface coverage of the material by the layer is between 70 and 100%, between 70 and 90%, between 80 and 100%, between 80 and 95%, between 90 and 100%, between 90 and 95%, including any range between. The terms “layer” and “QD layer” are used herein interchangeably.

[0066] In some embodiments, the layer has an average thickness of between 3 nm and 1mm, between 10 nm and 1mm, between 20 nm and 1mm, between 10 nm and 0.1mm, between 10 nm and lum, between 10 nm and lOOum, between 50 nm and lOOum, including any range between. In some embodiments, the layer has an average thickness equivalent to at least 2, at least 3, at least 5 times the average particle size of the QD.

[0067] In some embodiments, a weight ratio between the plurality of ligands and the QD within the substrate / layer is between 100: 1 and 1 : 100, between 100: 1 and 1 : 1, between 50: 1 and 1 : 1, including any range between.

[0068] In some embodiments, an average distance between adjacent QD within the layer is between 0.1 and lOOnm, between 0.1 and lOnm, between 1 and lOnm, between 1 and lOOnm, between 1 and 50nm, between 1 and 20nm, including any range between. In some embodiments, the term “average distance” refers to an average edge to edge distance of the adjacent QD, as determined aby image analysis of a micrograph (e.g. SEM image). In some embodiments, at least 50%, at least 70%, at least 80%, or at least 90% of the QD within the layer are in contact with at least one adjacent QD.

[0069] In some embodiments, the layer is stably bound to the material. In some embodiments, the substrate is characterized by a sufficient abrasion stability to be used as a part of a solarpanel, PV cell or a pane. In some embodiments, the abrasion stability of the substrate can be determined by abrasion test, tape test, etc.

[0070] In some embodiments, the plurality of ligands enhances the mechanical stability (e.g. abrasion stability) of the layer. In some embodiments, the layer comprising or consisting essentially of the QD and the plurality of ligands is characterized by a sufficient abrasion stability. Abrasion stability can be determined by any one of Falling Sand Abrasion Test (ASTM D968), Pencil Hardness Test (ASTM D3363) and Taber Linear Abraser (ASTM F2357). A layer with a sufficient abrasion stability is typically characterized by 2H-9H (ASTM D3363), or by weight loss of less than 10 mg after 1000 cycles under a 500 g load using CS- 10 abradant (ASTM F2357).

[0071] In some embodiments, the layer consist essentially of the QD and the plurality of ligands, as disclosed below. In some embodiments, the coating (or the layer) consists essentially of the QD and the plurality of ligands. In some embodiments, at least 90%, at least 95%, at least 97%, at least 99% by weight of the coating (or the layer) consists of the QD and the plurality of ligands. In some embodiments, the coating (or the layer) further comprises up to 5%w / w of an impurity, which is not the QD or the and the plurality of ligands.

[0072] In some embodiments, the material is selected from glass material, plastic material, ceramic material and metal material. In some embodiments, the material is a glass material. In some embodiments, the glass material comprises Indium tin oxide (ITO), or Fluorine doped tin oxide. In some embodiments, the glass material is tin oxide coated glass. In some embodiments, the outer surface of the glass material facing the QD is tin oxide coated (e.g. ITO, or Fluorine doped tin oxide coating). In some embodiments, the tin oxide coating further comprises a TiO2 layer on top of the tin oxide coating. In some embodiments, the TiO2 layer is in contact with the layer of QD.

[0073] In some embodiments, the substrate substantially maintains (at least 70%, at least 80%, at least 90%, at least 95%) of the light transparency of the pristine material devoid of the layer. In some embodiments, the substrate is characterized by light transparency of at least 70%, at least 80%, at least 90%, at least 95%, or between 70 and 99%, between 90 and 99% including any range between. Light transparency can be determined spectroscopically, using UV-Vis Spectrophotometer (at a wavelength between 400 and 600nm) or by ASTM DI 003.

[0074] In some embodiments, the outer surface is characterized by a mean contact angle of between 60 and 90 degrees, between 70 and 90 degrees, between 75 and 90 degrees, between 80 and 90 degrees or between 80 and 85 degrees including any range between.

[0075] In some embodiments, the outer surface is characterized by surface coverage (by the layer) ranging between 50 and 100%, between 70 and 90%, between 70 and 100%, between 80 and 100%, between 70 and 80%, between 90 and 100%, including any range between.

[0076] In some embodiments, the outer surface (also used herein as “substrate surface) is characterized by antibacterial activity. In some embodiments, the antibacterial activity comprises bacterial loading below 100 colony forming units (CFU), below 50 CFU, below 20 CFU, below 10 CFU, below 5 CFU, below 5 CFU, below 5 CFU, below 2CFU or below 1CFU per cm2of the substrate surface, including any range between.

[0077] In some embodiments, the antibacterial activity comprises prevention or reduction of biofilm formation on the substrate surface. In some embodiments, the antibacterial activity comprises bactericidal and / or bacteriostatic activity. The terms “antibacterial activity” and “antimicrobial activity” are used herein interchangeably.

[0078] Herein “antimicrobial activity” is referred to as an ability to inhibit (prevent), reduce or retard bacterial growth, spore and / or biofilm formation or eradicate living bacterial cells, or their spores, on the substrate surface.

[0079] In some embodiments, the “antimicrobial activity” refers to the ability to reduce a load of at least one pathogen (expressed in CFU or CFU / ml) on the substrate surface by at least 10, at least 20, at least 50, at least 100 fold, including any range between, wherein reduction is as compared to the same material devoid of the layer. In some embodiments, the “antimicrobial activity” refers to anti-biofilm activity.

[0080] Herein, inhibiting or reducing or retarding the formation of load of a microorganism refers to inhibiting, reducing, or retarding growth of microorganisms and / or eradicating a portion or all of an existing population of microorganisms.

[0081] The microorganism can be, for example, a unicellular microorganism (prokaryotes, archaea, bacteria, eukaryotes, protists, fungi, algae, molds, yeast, euglena, protozoan, dinoflagellates, apicomplexa, trypanosomes, amoebae and the likes), or a multicellular microorganism.

[0082] In some embodiments, the “antimicrobial activity” refers to anti-biofilm activity. In some embodiments, the “antimicrobial activity” refers to Gram-negative bactericidal and / or bacteriostatic activity. In some embodiments, the “antimicrobial activity” refers to Gramnegative bacterial biofilm activity. In some embodiments, the outer surface is devoid of Gramnegative bacterial biofilm.

[0083] In some embodiments, the microorganism comprises or consist of Gram-negative bacteria. In some embodiments, the Gram-negative bacteria comprises a bacterial genus selected from Pseudomonas, Salmonela and Escherichia. In some embodiments, the Gramnegative bacteria comprises E. coli, Salmonella Paratyphi B., or Pseudomonas aeruginosa, including any combination thereof.

[0084] The term "biofilm", as used herein, refers to an aggregate of living cells which are stuck to each other and / or immobilized onto a surface as colonies. The cells are frequently embedded within a self-secreted matrix of extracellular polymeric substance (EPS), also referred to as "slime", which is a polymeric sticky mixture of nucleic acids, proteins and polysaccharides. Microorganism growing in a biofilm may be physiologically distinct from cells in the "planktonic form" of the same organism, which by contrast, are single-cells that may float or swim in a liquid medium. Biofilms can go through several life-cycle steps which include initial attachment, irreversible attachment, one or more maturation stages, and dispersion. In the context of the present embodiments, the living cells forming a biofilm are Gram-negative bacteria.

[0085] The term "antibiofilm" refers to the capacity of the substrate to disturb the formation of a biofilm of bacterial, fungal and / or other cells, and / or to affect a reduction in the rate of buildup of a biofilm of bacterial, fungal and / or other cells, on a surface of the substrate.

[0086] As used herein, the term "preventing" in the context of antimicrobial, indicates that the growth rate of the microorganism cells is essentially nullified or is reduced by at least 20 %, at least 30 %, at least 40 %, at least 50 %, at least 60 %, at least 70 %, at least 80 %, at least 90 %, including any value therebetween, of the appearance of the microorganism in a comparable situation lacking the presence of the layer (i.e. QD layer). Each possibility represents a separate embodiment of the invention.

[0087] Alternatively, preventing means a reduction to at least 15%, 10%, or 5% of the appearance of the microorganism cells in a comparable situation lacking the presence of the layer.

[0088] As used herein, the term “reducing”, indicates that the growth rate (and or microbial loading expressed in CFU or CFU / ml) of the microorganism (including spores, cells, or biofilm thereof) is essentially reduced as compared to a similar substrate devoid of the layer.

[0089] In some embodiments, the term “essentially reduced” comprises at least 2 times, at least 5 times, at least 10 times, at least 50 times, at least 100 times, at least 1000 times, at least 10.000 times, at least 100.000 times, at least 1000.000 times, between 10 and 1000.000 times,between 100 and 1000.000 times, between 1000 and 10.000.000 times, between 1000 and 1000.000 times, between 10.000 and 1000.000 times CFU / ml reduction, including any range between, as compared to the CFU / ml content of a similar article devoid of the layer.

[0090] In some embodiments, the layer substantially prevents microbial infestation of the material / substrate. In some embodiments, the layer substantially prevents microbial infestation of the material / substrate upon exposing thereof to ambient conditions (e.g. ambient atmosphere comprising one or more microbes) for a time period between 1 day and 12 months, between 1 day and 6months, between 1 day and 2months, between 1 day and 1 month, between 1 and 20d, between 1 and 60d, between 1 and 50d, between 10 and 60d, between 1 and lOd, between 10 and 50d, between 10 and 40d, between 10 and 30d, including any range between. Methods for determining a level of appearance of a microorganism cells are known in the art.

[0091] In context of the present invention, the antimicrobial activity of the outer surface is determined by zone of inhibition (ZOI) test. ZOI test can be performed and evaluated based on Kirby-Bauer disk diffusion method, whereas the minimum size of ZOI corresponding to antimicrobial activity is around 6-10 millimeters, depending on the specific guidelines and interpretation used. Values below this threshold are generally classified as resistant, while larger zones indicate greater sensitivity or effectiveness of the antimicrobial agent. Zones between 10-15 mm may be classified as moderately sensitive or intermediate, depending on the specific guidelines. Zones of 15 mm or larger are typically categorized as highly sensitive or susceptible to the antimicrobial agent.

[0092] The antimicrobial activity of the outer surface corresponds to ZOI of at least 6 mm, at least 10, at least 15mm, or between 6 and 40mm, between 10 and 40mm, between 15 and 40mm, between 20 and 40mm, between 10 and 35mm, between 15 and 35mm, including any range between.

[0093] The substrate disclosed herein maybe a part of an article, such as a protective cover, optical device, a solar panel, pane, etc. or any protective light transparent substrate exposed to ambient. In another aspect, there is provided an article, comprising the substrate of the invention. In some embodiments, the article is a solar cell.Method of manufacture

[0094] In another aspect, there is a method for preparing the substrate of the invention comprising applying a mixture comprising the QD on a surface of the material to obtain a coated material; and drying the coated material, thereby obtaining the substrate. In some embodiments, the method is for providing antimicrobial properties to a material.

[0095] In another aspect, the method for preparing the substrate of the invention comprises: applying a mixture comprising the QD to the at least one surface of the material wherein the QD are bound to the first ligand, wherein the first ligand is as described above; performing a ligand exchange, to obtain a coated material comprising the QD bound to the second ligand; and optionally drying the coated material, thereby obtaining the substrate.

[0096] In some embodiments, the method is for providing antimicrobial properties to a material.

[0097] In some embodiments, applying and drying are performed subsequently. In some embodiments, the coated material is characterized by a coating thickness between lOOnm and 10mm, including any range between.

[0098] In some embodiments, the mixture is dispersion comprising the QD dispersed in an organic solvent. In some embodiments, the mixture further comprises an additive, a stabilizer, a dispersant, or any combination thereof. In some embodiments, the mixture is devoid of an additive, a stabilizer or a dispersant.

[0099] In some embodiments, the organic solvent is a volatile organic solvent. In some embodiments, the volatile organic solvent has a vapor pressure at ambient temperature (20- 25°C) of greater than 5 mmHg (~ 667 Pa), greater than 20mmHg, greater than 50mmHg, or greater than lOOmmHg.

[0100] In some embodiments, the organic solvent is selected from an aliphatic organic solvent, an aromatic organic solvent, a ketone-based solvent, an ether-based solvent, an ester- based solvent, alcohol (e.g. lower alcohols such as methanol, ethanol, n-butanol, tert-butanol or propanol), a halogenated solvent (e.g. chlorinated organic solvent), or any combination thereof.

[0101] Non-limiting examples of organic solvents (e.g., aliphatic hydrocarbons) include but are not limited to: pentane, hexane, cyclohexane, octane, heptane, or any combination thereof. Other aliphatic hydrocarbon solvents are well known in the art, such as ethyl ether, methyl ethyl ketone (MEK), methylisobutylketone, dichloromethane, chloroform, aliphatic esters (such as ethyl acetate).

[0102] Non-limiting examples of aromatic solvents include but are not limited to toluene, ethylbenzene, xylene, chlorobenzene, styrene, di chlorobenzene, nitrobenzene, trimethylbenzene, trichlorobenzene or any combination thereof.

[0103] Non-limiting examples of chlorinated organic solvent include but are not limited to Chloroform, Carbon tetrachloride, Methylene chloride (Dichloromethane), Trichloroethylene,Tetrachloroethylene (Perchloroethylene), 1,1,1 -Tri chloroethane, Chlorobenzene, andDichlorobenzene, or any combination thereof.

[0104] In some embodiments, the organic solvent is or comprises hexane, DCM, etc.

[0105] In some embodiments, a concentration of the QD in the mixture is between 1 and 100 mg / ml, between 1 and 50 mg / ml, between 10 and 100 mg / ml, between 10 and 20 mg / ml, between 10 and 50 mg / ml, including any range between. In some embodiments, a concentration of the QD in the mixture is between 10 and 30 mg / ml, or about 20 mg / ml.

[0106] In some embodiments, the ligand exchange comprises applying the second ligand to the at least one surface. In some embodiments, the second ligand is applied in a form of a solution or a dispersion. In some embodiments, a solution of the second ligand to the at least one surface, wherein the solution comprises an organic solvent. In some embodiments, the solution of the second ligand comprises the same solvent as the mixture of QD. In some embodiments, the solution of the second ligand comprises a first solvent and the mixture of QD comprises a second solvent, wherein the first and second solvent are distinct species.

[0107] In some embodiments, the organic solvent of the solution is a volatile solvent disclosed above.

[0108] In some embodiments, the applying step is performed by a process selected from dropcasting, coating, spin coating, spray coating, flow coating, dip coating, extrusion coating, transfer coating, and printing, or any combination thereof.

[0109] In some embodiments, the drying step is performed by conventional drying methods, such as thermal drying, convectional drying, vacuum drying, etc.

[0110] In some embodiments, a concentration of the second ligand in the solution is between 0.01 and IM, between 0.01 and 0.2M, or about 0.1M, including any range between.

[0111] In some embodiments, the ligand exchange is performed by contacting the solution with the at least one surface, wherein contacting is performed for a time period of at least Is, at least 10s, at least Im, between 10s and Ih, between 10s and lOmin, including any range between.

[0112] In some embodiments, the steps of applying and ligand exchange are performed at a temperature between -20 and 50C, between 0 and 50C, between 0 and 40C, between -20 and 30C, between 10 and 50C, between 10 and 30°C, including any range between.

[0113] In some embodiments, the ligand exchange is performed after drying or after the applying step. In some embodiments, the ligand exchange is performed by contacting the substrate with the second ligand or a liquid composition comprising same. In some embodiments, the contacting is by dipping, drop-casting, coating, spin coating, spray coating,flow coating, dip coating, extrusion coating, transfer coating, and printing, or any combination thereof.

[0114] In some embodiments, the second ligand is the ligand disclosed hereinabove. In some embodiments, the second ligand is PDA. In some embodiments, the method further comprises a step of rinsing the substrate (i.e. to remove excess of unbound ligand / QD or both), and / or drying the substrate (i.e. to remove the solvent).

[0115] In some embodiments, the material is selected from glass material, plastic material, ceramic material and metal material. In some embodiments, the material is a glass material. In some embodiments, the glass material comprises Indium tin oxide (ITO), or Fluorine doped tin oxide. In some embodiments, the glass material is tin oxide coated glass. In some embodiments, the outer surface of the glass material is tin oxide coated (e.g. ITO, or Fluorine doped tin oxide coating). In some embodiments, the tin oxide coating further comprises a TiO2 layer on top of the tin oxide coating.

[0116] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.General Definitions

[0117] As used herein the term “about” refers to ± 10 %.

[0118] The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to".

[0119] The term “consisting of means “including and limited to”.

[0120] The term "consisting essentially of means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0121] The word “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and / or to exclude the incorporation of features from other embodiments.

[0122] The word “optionally” is used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the invention may include a plurality of “optional” features unless such features conflict.

[0123] As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

[0124] Although embodiments of the invention are not limited in this regard, discussions utilizing terms such as, for example, “processing,” “computing,” “calculating,” “determining,” “establishing”, “analyzing”, “checking”, or the like, may refer to operation(s) and / or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and / or transforms data represented as physical (e.g., electronic) quantities within the computer’s registers and / or memories into other data similarly represented as physical quantities within the computer’s registers and / or memories or other information non-transitory storage medium that may store instructions to perform operations and / or processes.

[0125] Although embodiments of the invention are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. The term “set” when used herein may include one or more items.

[0126] In the discussion unless otherwise stated, adjectives such as “substantially” and “about” modifying a condition or relationship characteristic of a feature or features of an embodiment of the invention, are understood to mean that the condition or characteristic is defined to within tolerances that are acceptable for operation of the embodiment for an application for which it is intended. Unless otherwise indicated, the word “or” in the specification and claims is considered to be the inclusive “or” rather than the exclusive or, and indicates at least one of, or any combination of items it conjoins.

[0127] It should be understood that the terms “a” and “an” as used above and elsewhere herein refer to “one or more” of the enumerated components. It will be clear to one of ordinary skill in the art that the use of the singular includes the plural unless specifically stated otherwise. Therefore, the terms “a”, “an” and “at least one” are used interchangeably in this application.

[0128] For purposes of better understanding the present teachings and in no way limiting the scope of the teachings, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims,are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0129] In the description and claims of the present application, each of the verbs, “comprise”, “include”, and “have” and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of components, elements or parts of the subject or subjects of the verb.

[0130] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0131] Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0132] As used herein, the term “substantially” refers to at least 80%, at least 85%, at least 90%, at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, including any range or value therebetween. Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging / ranges between” a first indicate number and a second indicate number and “ranging / ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

[0133] Further, all numerical values, e.g. when referring the amounts or ranges of the elements constituting the formulation are approximations which are varied (+) or (-) by up to20%, at times by up to 10% of from the stated values. It is to be understood, even if not always explicitly stated that all numerical designations are preceded by the term "about".

[0134] The term “consisting essentially of’ is used to define formulations which include the recited elements but exclude other elements that may have an essential significance on the formulation. “Consisting of’ shall thus mean excluding more than trace elements of other elements. Embodiments defined by each of these transition terms are within the scope of this invention. As used herein the term "method" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.

[0135] As used herein, the term “treating” includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition.

[0136] As used herein, the term "alkyl" describes an aliphatic hydrocarbon including straight chain and branched chain groups. In some embodiments, the alkyl group has 1 to 20 carbon atoms, between 1 and 10, between 1 and 5, between 5 and 10, between 10 and 15, between 15 and 20, including any range between.

[0137] In some embodiments, the alkyl encompasses a short alkyl and / or a long alkyl. In some embodiments, the alkyl has from 21 to 100 carbon atoms, or more. In the context of the present invention, a "long alkyl" is an alkyl having at least 20 carbon atoms in its main chain (the longest path of continuous covalently attached atoms). A short alkyl therefore has 20 or less (e.g. 2, 3, 4, 5, 6, 8, 10, 15, or 20) main-chain carbons. The alkyl can be substituted or unsubstituted, as defined herein.

[0138] The term "alkyl", as used herein, also encompasses saturated or unsaturated hydrocarbon, hence this term further encompasses alkenyl and alkynyl.

[0139] The term "alkenyl" describes an unsaturated alkyl, as defined herein, having at least two carbon atoms and at least one carbon-carbon double bond. The alkenyl may be substituted or unsubstituted by one or more substituents, as described hereinabove.

[0140] The term "alkynyl", as defined herein, is an unsaturated alkyl having at least two carbon atoms and at least one carbon-carbon triple bond. The alkynyl may be substituted or unsubstituted by one or more substituents, as described hereinabove.

[0141] The term "cycloalkyl" describes an all-carbon monocyclic or fused ring (i.e. rings which share an adjacent pair of carbon atoms) group where one or more of the rings does not have a completely conjugated pi-electron system. The cycloalkyl group may be substituted or unsubstituted, as indicated herein.

[0142] The term "aryl" describes an all-carbon monocyclic or fused-ring polycyclic (i.e. rings which share adjacent pairs of carbon atoms) groups having a completely conjugated pi-electron system. The aryl group may be substituted or unsubstituted, as indicated herein.

[0143] The term "alkoxy" describes both an O-alkyl and an -O-cycloalkyl group, as defined herein. The term "aryloxy" describes an -O-aryl, as defined herein.

[0144] Each of the alkyl, cycloalkyl and aryl groups in the general formulas herein may be substituted by one or more substituents, whereby each substituent group can independently be, for example, halide, alkyl, alkoxy, cycloalkyl, nitro, amino, hydroxyl, thiol, thioalkoxy, carboxy, amide, aryl and aryloxy, depending on the substituted group and its position in the molecule. Additional substituents are also contemplated.

[0145] The term "halide", "halogen" or “halo” describes fluorine, chlorine, bromine or iodine. The term “haloalkyl” describes an alkyl group as defined herein, further substituted by one or more halide(s). The term “haloalkoxy” describes an alkoxy group as defined herein, further substituted by one or more halide(s). The term “hydroxyl” or "hydroxy" describes a -OH group. The term "mercapto" or “thiol” describes a -SH group. The term "thioalkoxy" describes both an -S-alkyl group, and a -S-cycloalkyl group, as defined herein. The term "thioaryloxy" describes both an -S-aryl and a -S-heteroaryl group, as defined herein. The term “amino” describes a -NR’R” group, or a salt thereof, with R’ and R” as described herein.

[0146] The term "heterocyclyl" describes a monocyclic or fused ring group having in the ring(s) one or more atoms such as nitrogen, oxygen and sulfur. The rings may also have one or more double bonds. However, the rings do not have a completely conjugated pi-electron system. Representative examples are piperidine, piperazine, tetrahydrofuran, tetrahydropyran, morpholino and the like.

[0147] The term "carboxy" describes a -C(O)OR' group, or a carboxylate salt thereof, where R' is hydrogen, alkyl, cycloalkyl, alkenyl, aryl, heteroaryl (e.g. optionally bonded through a ring carbon, or through a heteroatom) or heterocyclyl (e.g. optionally bonded through a ring carbon, or through a heteroatom) as defined herein.

[0148] In some embodiments, R' and R" are the same or different, wherein each of R' and R" is independently selected from hydrogen, alkyl, cycloalkyl, alkenyl, aryl, heteroaryl (e.g.optionally bonded through a ring carbon, or through a heteroatom) or heterocyclyl (e.g. optionally bonded through a ring carbon, or through a heteroatom) as defined herein.

[0149] The term “carbonyl” describes a -C(O)R' group, where R' is as defined hereinabove. The above-terms also encompass thio-derivatives thereof (thiocarboxy and thiocarbonyl).

[0150] The term “thiocarbonyl” describes a -C(S)R' group, where R' is as defined hereinabove. A "thiocarboxy" group describes a -C(S)OR' group, where R' is as defined herein. A "sulfinyl" group describes an -S(O)R' group, where R' is as defined herein. A "sulfonyl" or “sulfonate” group describes an -S(O)2R' group, where R' is as defined herein.

[0151] A "carbamyl" or “carbamate” group describes an -OC(O)NR'R" group, where R' is as defined herein and R" is as defined for R'. A "nitro" group refers to a -NO2 group. The term "amide" as used herein encompasses C-amide and N-amide. The term "C-amide" describes a - C(O)NR'R" end group or a -C(O)NR' -linking group, as these phrases are defined hereinabove, where R' and R" are as defined herein. The term "N-amide" describes a -NR"C(O)R' end group or a -NR'C(O)- linking group, as these phrases are defined hereinabove, where R' and R" are as defined herein.

[0152] A"cyano" or "nitrile" group refers to a -CN group. The term "azo" or "diazo" describes an -N=NR' end group or an -N=N- linking group, as these phrases are defined hereinabove, with R' as defined hereinabove. The term "guanidine" describes a -R'NC(N)NR"R"' end group or a -R'NC(N) NR" - linking group, as these phrases are defined hereinabove, where R', R" and R'" are as defined herein. As used herein, the term “azide” refers to a -N3 group. The term “sulfonamide” refers to a -S(O)2NR'R" group, with R' and R" as defined herein.

[0153] The term “phosphonyl” or “phosphonate” describes an -OP(O)-(OR')2 group, with R' as defined hereinabove. The term “phosphinyl” describes a -PR'R" group, with R' and R" as defined hereinabove. The term “alkylaryl” describes an alkyl, as defined herein, which substituted by an aryl, as described herein. An exemplary alkylaryl is benzyl.

[0154] The term "heteroaryl" describes a monocyclic or fused ring (i.e. rings which share an adjacent pair of atoms) group having in the ring(s) one or more atoms, such as, for example, nitrogen, oxygen and sulfur and, in addition, having a completely conjugated pi-electron system. As used herein, the term “heteroaryl” refers to an aromatic ring in which at least one atom forming the aromatic ring is a heteroatom. Heteroaryl rings can be foamed by three, four, five, six, seven, eight, nine and more than nine atoms. Heteroaryl groups can be optionally substituted. Examples of heteroaryl groups include, but are not limited to, aromatic C3-8 heterocyclic groups containing one oxygen or sulfur atom, or two oxygen atoms, or two sulfur atoms or up to four nitrogen atoms, or a combination of one oxygen or sulfur atom and up totwo nitrogen atoms, and their substituted as well as benzo- and pyrido-fused derivatives, for example, connected via one of the ring-forming carbon atoms. In certain embodiments, heteroaryl is selected from among oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, pyridinyl, pyridazinyl, pyrimidinal, pyrazinyl, indolyl, benzimidazolyl, quinolinyl, isoquinolinyl, quinazolinyl or quinoxalinyl.

[0155] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0156] The descriptions of the various embodiments of the present invention have been presented for purposes of illustration but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

[0157] Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.EXAMPLES

[0158] Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non-limiting fashion.Materials and methodsMaterials

[0159] Tri-n-octyl phosphine (TOP) (90% tech.), Te powder (99.999%), squalane (99%), lead acetate trihydrate (Pb(C2H3O2)2*3(H2O)), (99%), oleic acid (OA) (90% tech), and p-phenylene diamine (PDA) (97+%) were obtained from Holand Moran; methanol (AR), and hexane (95%), were purchased from BioLab; ethanol (99.5%) and isopropanol (<99.8% tech.) were purchased from Romical; indium-titanium oxide (ITO) glass substrates, helmanex III were attained fromOsilla; Ti-Nanoxide BL / SC (Solaronix); deionized water (> 18.0 MQcm'1). All chemicals are used as purchased without further purification. Tri-n-octyl phosphine (TOP) (90% tech.), Te powder (99.999%), squalane (99%), lead acetate trihydrate (Pb(C2H3O2)2*3(H2O)), (99%), oleic acid (OA) (90% tech), and p-phenylene diamine (PDA) (97+%) were obtained from Holand Moran; methanol (AR), and hexane (95%), were purchased from BioLab; ethanol (99.5%) and isopropanol (<99.8% tech.) were purchased from Romical; indium-titanium oxide (ITO) glass substrates, helmanex III were attained from Osilla; Ti-Nanoxide BL / SC (Solaronix); deionized water (> 18.0 MQcm'1). All chemicals are used as purchased without further purification.Synthesis of PbTe QDs

[0160] 6.1 ± 0.5 nm PbTe QDs were synthesized in a three-neck round-bottom flask under N2 gas using the standard Schlenk line technique. 570 mg (1.5 mmol) of Pb acetate trihydrate (Pb(C2H3O2)2*3(H2O)), 1 mL (3.2 mmol) of oleic acid (OA), 14 mL of squalene, and 6 mL of 0.5 M tellurium-tri-n-octyl phosphine (TOP-Te) solution were used. The solution was stirred overnight until all the tellurium powder was completely dissolved, and the solution turned transparent and yellow. Pb salt, OA, and squalene were mixed and heated to 40°C under vacuum for 15 minutes. Subsequently, the reaction mixture was heated to 100°C and kept at this temperature for an additional 45 minutes. The vacuum was replaced with N2 gas, and the mixture was heated to 180°C. 6 mL of a 0.5 M TOP-Te solution was rapidly injected into the reaction mixture. The reaction temperature dropped to ~155°C and was held at this temperature (± 2°C) for 2 minutes. The reaction was quenched in a water bath to room temperature. The mixture was washed with 10 mL of hexane in a 50 mL centrifuge tube. The particles were centrifuged for 5 min at 4000 rpm. Further, 20 mL of ethanol was added, and the tube was centrifuged for 5 min at 4000 rpm. The supernatant was disposed of, and the particles were washed with ethanol and redispersed in 10 mL of hexane. The 9.8 ± 0.7 nm and 13.2 ± 1.1 nm QDs were synthesized with the same protocol, changing the OA volume and TOP-Te concentration. For 9.8 nm QD synthesis, 3 mL of OA, 12 mL of squalene and 6 mL of 0.75 M TOP-Te were added to the reaction. For 13.2 nm QD synthesis, 6 mL of OA, 9 mL of squalene, and 6 mL of 0.75 M TOP-Te were used.Layers Fabrication Solid-State Ligand Exchange

[0161] The ITO glass substrates were used as purchased, applying a cleaning procedure provided by the supplier. Ti-nanoxide (TiO2) deposition on the ITO glass substrate was performed in a N2 glove box. TiO2 lowers the surface roughness on ITO and promotesfabrication of uniform monolayers of thin film

[0033] , 50 / / I of Ti -nanoxi de solution was drop- casted, in a static regime, on the ITO glass substrates and spun in a spin coater at 5000 rpm for 30 seconds. The deposited TiO2 layers were annealed at 550°C for one hour under 6 L / min air flow in a tube furnace with a heat acceleration of 5°C / min. This step marked the end of the fabrication process for the TiO2 on ITO (TiO2 / ITO) glass substrates used as control. Further, 80 jil PbTe QDs with a concentration of 20 mg / mL were drop-casted on a TiO2 / ITO glass substrate in the static regime and spun at 3000 rpm spinning speed for 30 seconds. The prepared PbTe on TiO2 / ITO (PbTe / TiO2 / ITO) layers were dried under air for 30 minutes for further use. At the end of this stage, some samples were set aside (and marked ‘No LE’) to test the effect of the QDs without the organic ligand.

[0162] Solid-state ligand exchange (LE) was performed in 0.1 M PDA in MeOH solution. The fabricated PbTe / TiCh / ITO layer was placed in a Petri dish containing 5 mL of 0.1 M PDA, ensuring that the PDA solution fully enveloped the entire substrate. Solid-state LE was performed for 5 minutes. After rinsing the fabricated layer with methanol three times to remove the excess PDA, the layer was dried using N2 flow. PbTe QD deposition and solid-state LE were performed two times on each TiCh / ITO glass substrate to ensure full substrate surface coverage.Layers Characterization

[0163] All samples were analysed using a high-resolution scanning electron microscope (HR- SEM) (Ultra-High-Resolution Maia 3 FE-SEM, Tescan). The QDs size and morphology were analysed using a STEM (bright) detector and an electron beam voltage of 25-30 kV. Samples were prepared by drop casting on a copper grid. The particle size and count generator program was used for PbTe-QDs size calculations. All the image processing was performed by the threshold function. Energy-dispersive X-ray spectroscopy (EDS) analysis of the layers was obtained by the Aztec microanalytic system (Oxford Instruments). Contact angle measurements were carried out using a digital microscope (HD multi -function digital microscope). The contact angle of 2 pL of double-distilled water on the PbTe layer surfaces was measured at four different locations and averaged to give an estimate of the surface wettability.Antibacterial Assay

[0164] Cultures of Gram -positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coH. Salmonella Paratyphi B and Pseudomonas aeruginosa were grown on Brain Heart agar plates (BHA, Acumedia, Lansing, MI, USA) for 24 h, transferred intoBrain Heart broth (BH, Acumedia, Lansing, MI, USA), grown at 37 ± 1°C with shaking at 170 rpm until reaching the absorbance of ODeeo ~ 0.3, diluted with commercially available sterile 0.9% saline solution to ODeeo = 0.10 ± 0.02, which corresponded to a cell concentration of 108CFU mL'1. The cells were diluted using saline to the final concentration of 106CFU mL'1. Then, 0.1 mL of the bacterial suspension was spread on BH agar plates. Then the PbTe QD layers under investigation and blank controls (TiO2 / ITO glasses) were placed on plates, and the plates were incubated overnight at 37 ± 1°C in the dark. For each test, the antibacterial activity was assessed by measuring the diameter of the zone of bacterial growth inhibition observed after incubation.FTIR Microscope Measurement

[0165] FTIR microscope imaging was performed on an infrared microscope (Jasco, IRT- 5200-16, Tokyo, Japan) coupled to an FTIR spectrometer (Jasco, 6800 FV, Tokyo, Japan). The 16x Cassegrain objective was used for all measurements in reflection mode and the lattice measurement option. The aperture was set to 50 pm x 50 pm per measurement point over a 6 x 6 square lattice. The radiation from the IR source of the spectrometer was focused on randomly selected points on the substrate, and the output radiation was reflected onto a liquid nitrogen cooled, mid-band MCT (mercury cadmium telluride) detector. Two measurements were carried out on each substrate in the spectral range of 650-4000 cm-1and each spectrum was an average over 32 scans. Before each measurement, a background was measured on a portion of the substrate observed to be clear of bacteria.Data Processing

[0166] All data processing procedures were carried out using the OriginPro software package (OriginPro Version 2023b, OriginLab Corporation, Northampton, MA, USA) and ImageJ software version 1.54f (Image Processing and Analysis in Java - Wayne Rasband and contributors, National Institutes of Health, Bethesda, MD, USA, public domain license, https: / / imagej.nih.gov / ij / ). Spectra obtained from FTIR micro-spectroscopy were cut to the region 1000 - 1800 cm'1, smoothed using the 18-side point Savitzky-Golay method, baseline corrected, and normalized to the peak around 1640 cm'1(C=O stretching vibration of amide I proteins) before further analysis.EXAMPLE 1Characterization of PbTe Layered Substrates

[0167] The EDS spectrum of the PbTe nanoparticles presented in Figure 1(A) confirms the presence of Pb (48.6%) and Te (51.4%) in the approximate stoichiometric ratio of PbTecompounds. The SEM image in Figure 1(B) displays PbTe nanoparticles that are evenly distributed and have a spherical morphology. The average particle size falls within the range of 6.1 ± 0.5 nm, as shown in Figure 1C. The SEM image in Fig ID displays 13.2 nm PbTe nanoparticles that are evenly distributed and have a cubic morphology.

[0168] FTIR spectroscopy (Fig 6) shows transmittance peaks around wavenumbers that have been reported for PbTe nanocrystals synthesized through various routes. The peaks at 2852 cm'1and 2921 cm'1have been observed in electrodeposited PbTe films and attributed to antistretching -CEE and stretching -CH vibration modes, respectively. The peaks around 1377 cm'1and 1462 cm'1were assigned to in-plane deformations in -CH3 and -CH2 respectively, while that observed at 2955 cm'1is due to asymmetric -CH3 stretch. The absorptions between 800 cm'1and around 1000 cm'1were attributed to -CH2 rocking modes. Fig 4 shows results of UV- Vis transmission measurements on PbTe layer compared to TiCh / ITO substrate, indicating that for up to five layers of PbTe quantum dots, the coatings are largely transparent especially between 400 nm to 1100 nm, which is considered an important optical absorption region, for example, in silicon based solar cells.

[0169] The contact angle of double-distilled water on the surfaces before and after layering showed values that were significantly higher for the layered substrates than the blank controls (p<0.01). The mean contact angles on the blank controls, the PbTe layers with LE and the PbTe layers without LE were found to be 61.5 ± 2.0, 82.8 ± 4.8, and 82.1 ± 5.2 degrees, respectively. Zone of Inhibition of PbTe QDs Layered ITO glass Substrates

[0170] The antibacterial efficacy of PbTe QD layers, fabricated on TiO2 / ITO glass substrates, was evaluated against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coH. Salmonella Paratyphi B and Pseudomonas aeruginosa. The zone of inhibition (ZOI) for each bacteria type was determined using the PbTe layers, with and without LE. Blank TiCh / ITO glasses of the same size were used as control. Figure 2 shows an example of the observed ZOI for 6.1 nm PbTe QD layers tested on the four bacterium types used in this study. It can be seen this material provides well-defined growth inhibition zones, except for S. aureus. The control did not show the inhibition effect on bacteria. A summary of the diameters of the ZOI is presented in Figure 3. The diameter values ranged from 26 - 35 mm for E. coH. 26 - 30 mm for S. Paratyphi B, and 18 - 26 mm for P aeruginosa. The effect was between negligible and sparse for the S. aureus. Layer functionalization with the organic ligand was observed to increase slightly the antibacterial properties of the PbTe QDs.FTIR Analysis of Bacteria on PbTe QDs layers

[0171] FTIR analysis showed that there were fewer bacterial colonies on substrates with PbTe QD layers than on the blank controls. The absolute peak-to-peak height around 1540 cm'1, related to amide II protein absorption, an extensively reported peak in the mid-IR profile of bacteria, was used to infer bacterial presence in the scanned regions. Figure 4 shows color maps based on 6 x 6 measurement-point squares from FTIR micro-spectroscopic imaging of S. Paratyphi B bacteria on the blank and PbTe-layered substrates. For the layered substrates, the scanned regions showed mostly no or much lower absorption intensities (bluer appearance) on the chosen discriminatory wavenumber compared to the blank controls (mostly redder appearance). This indicates, in line with Beer-Lambert law, that thicker bacteria layer on the blank controls absorb more radiation compared to the layered substrates with mostly no bacteria. The color maps for S. aureus (not shown) showed intense absorptions, indicative of widespread bacteria colonization across substrate surfaces and the reduced effect of the QDs on the Gram-positive strain.

[0172] To compare the absorption profiles of the bacteria on the control and layered substrates, measured spectra were normalized to the amide I peak around 1640 cm'1. Examples of the normalized spectra for each bacteria type in the region 1000-1800 cm'1are presented in Figure 5. On Figures 5 (A-C), it can be observed that for the bacteria on the PbTe QDs layers, there is a significant increase in the peaks around 1080 cm'1and 1400 cm'1compared to the blanks, and the peak around 1150 cm'1which is almost absent in the spectra of bacteria on the blank substrates. These peaks are, respectively, related to symmetric PO2' vibrations in nucleic acids, symmetric COO' vibrations in amino acids, and phosphodiester vibrations

[0029] , They relate to RNA and DNA contents, and the observed increase could suggest a disruption of cell membrane integrity leading to leakage of cytoplasmic contents, including nuclear materials, and ultimately an increased infrared absorption on these bands.

[0173] The tested PbTe QDs layers showed notable antibacterial effect on Gram -negative Escherichia coH. Salmonella Paratyphi B, and Pseudomonas aeruginosa. However, a negligible effect was observed for Gram-positive Staphylococcus aureus. Accordingly, it is postulated that the substrate of the invention has specific / selective antibacterial activity against Gram-negative bacteria.

[0174] Given the stability of the PbTe layers on the substrates and the observed antibacterial property, they can be considered for surface finishing of bacterial -prone surfaces like hospital bedside tabletops, shower handles, bed rails, and soap dispenser handles, among others. These l ' lsurfaces have been reported as significant targets for bacterial contamination in healthcare facilities, making them pathways for HAIs, which is a current public health challenge.

[0175] The contact angles of water on layered substrates were found to be significantly greater than those on blank substrates (p<0.01), indicative of a decrease in hydrophilicity / wettability of the substrates upon layering with the PbTe QDs. A decrease in wettability implies less adhesion, which is a preferred property for antibacterial surfaces. After each experiment, we observed attachment of dead bacteria to the layer surface. The inventors found that by autoclaving at 120°C, the antibacterial effect of the layers is maintained. Figure S4 shows the antibacterial effect observed after autoclaving layered substrates.

[0176] Within the range of particle sizes used in our experiments (6-13 nm), antibacterial effect of PbTe QD layers was not observed to vary significantly with size. The ligand functionalization improved the stability of the QDs on the substrates.

[0177] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0178] All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

Claims

CLAIMS1. A substrate comprising at least one surface, said at least one surface comprises:• a material in contact with PbTe quantum dots (QD), wherein the QD are located on an outer surface of the material;• wherein the QD are characterized by an average particle size in a range between 1 and 20 nm; and wherein each of the QD comprises a plurality of ligands bound to the QD, wherein said bound is via a covalent bond, a non-covalent bond or via a coordinative bond; and• wherein the plurality of ligands comprises a second ligand comprising an aromatic compound.

2. The substrate of claim 1, wherein said at least one surface is (i) devoid of a biofilm; (ii) is characterized by a bacterial loading below 10 colony forming units (CFU) per cm2, or both (i) and (ii).

3. The substrate of claim 1 or 2, wherein said at least one surface is characterized by antibacterial activity, wherein the antibacterial activity comprises bactericidal and / or bacteriostatic activity.

4. The substrate of any one of claims 1 to 3, wherein the plurality of ligands further comprises a first ligand comprising a fatty acid.

5. A substrate comprising at least one surface:• said at least one surface comprises a material in contact with PbTe quantum dots (QD), wherein the QD are bound to an outer surface of the material,• wherein the QD are characterized by an average particle size in a range between 1 and 20 nm; and wherein the at least one surface is (i) characterized by a bacterial loading below 10 colony forming units (CFU) per cm2; (ii) devoid of biofilm, or both (i) and (ii).

6. The substrate of any one of claims 1 to 5, wherein the QD form a layer on top of the material within said at least one surface.

7. The substrate of any one of claims 1 to 6, wherein the material is selected from glass, plastic, ceramics and metal.

8. The substrate of any one of claims 1 to 7, wherein the QD are crystalline as determined by X-ray spectroscopy and are spherically shaped, cubically shapedor both.

9. The substrate of any one of claims 6 to 8, wherein an average distance between two adjacent QD within the layer is 0. l-10nm.

10. The substrate of any one of claims 1 to 9, wherein the average particle size of the QD is between 3 and 15nm.

11. The substrate of any one of claims 1 to 10, wherein the average particle size is between 4 and 15nm.

12. The substrate of any one of claims 1 to 11, wherein the average particle size of the QD is between 5 and 15nm.

13. The substrate of any one of claims 1 to 12, wherein the average particle size of the QD is between 5 and lOnm, and the QD are spherically shaped and wherein the average particle size is determined based on SEM image.

14. The substrate of any one of claims 1 to 12, wherein the average particle size of the QD is between 11 and 15nm, and the QD are cubically shaped; and wherein the average particle size is determined based on SEM image.

15. The substrate of any one of claims 1 to 14, wherein the stoichiometric ratio of Pb in the QD is between 48 % and 52 %, as determined by EDS.

16. The substrate of anyone of claims 6 to 15, wherein the layer has an average thickness of between 3 nm and 1mm and is characterized by surface coverage of 70-100%.

17. The substrate of any one of claims 1 to 16, wherein said at least one surface is characterized by a water contact angle between 60 and 90 degrees.

18. The substrate of claim 17, wherein the water contact angle is between 80 and 85 degrees.

19. The substrate of any one of claims 5 to 18, further comprising a plurality of ligands bound to the QD.

20. The substrate of claim 19, wherein the plurality of ligands comprises a second ligand; and wherein the second ligand comprises an aromatic compound.

21. The substrate of any one of claims 1 to 4 and 20, wherein the aromatic compound comprises one or more functional groups selected from thiol, amine, and carboxy, including any salt and any combination thereof.

22. The substrate of any one of claims 1 to 4 and 20-21, wherein the aromatic compound comprises an amino phenyl.

23. The substrate of claim 22, wherein the amino phenyl is a phenyl diamine.

24. The substrate of claim 23, wherein the phenyl diamine is p-phenylene diamine (PDA).

25. The substrate of claim 19 or 20, wherein the plurality of ligands further comprises a first ligand; and wherein the first ligand is or comprises a fatty acid.

26. The substrate of claim 4 or 25, wherein the fatty acid is a C2-C30 fatty acid.

27. The substrate of claim 26, wherein the C2-C30 fatty acid is a C5-C20 fatty acid.

28. The substrate of claim 26 or 27, wherein the C2-C30 fatty acid is a C12-C20 fatty acid.

29. The substrate of claim 28, wherein the C12-C20 fatty acid is oleic acid.

30. The substrate of any one of claims 1 to 29, wherein the at least one surface has antibacterial activity, wherein the antibacterial activity comprises bactericidal and / or bacteriostatic activity.

31. The substrate of claim 30, wherein the antibacterial activity comprises Gram-negative bacteria bactericidal and / or bacteriostatic activity.

32. The substrate of any one of claims 1 to 31, wherein said biofilm is a Gram-negative bacteria biofilm.

33. The substrate of any one of claims 2 to 32, wherein the bacterial loading is Gramnegative bacteria loading.

34. The substrate of any one of claims 31 to 33, wherein the Gram-negative bacteria comprise E. coli, Salmonella Paratyphi B., or Pseudomonas aeruginosa, including any combination thereof.

35. The substrate of any one of claims 30 to 34, wherein the antibacterial activity is maintained after exposing said substrate to a temperature of at least 120 °C.

36. The substrate of any one of claims 30 to 35, wherein the antibacterial activity is determined by zone of inhibition test.

37. The substrate of any one of claims 30 to 36, wherein said material is or comprises glass.

38. An article comprising the substrate of any one of claims 1 to 37.

39. The article of claim 38, selected from a solar panel and a pane.

40. A method for preparing the substrate of any one of claims 1 to 39, comprising:• applying a mixture comprising the QD to the at least one surface of the material , wherein the QD are bound to the first ligand;• performing a ligand exchange, to obtain a coated material comprising the QD bound to the second ligand; and• drying the coated material, thereby obtaining the substrate.

41. The method of claim 40, wherein the mixture is a dispersion of the QD in a volatile organic solvent.

42. The method of claim 41, wherein said volatile organic solvent is selected form an aliphatic hydrocarbon solvent, chlorinated organic solvent and an aromatic solvent.

43. The method of claim 41 or 42, wherein said volatile organic solvent is hexane.

44. The method of any one of claims 40 to 43, wherein said applying comprises dropcasting, coating, spin coating, spray coating, flow coating, dip coating, extrusion coating, transfer coating, and printing, or any combination thereof.

45. The method of any one of claims 40 to 43, wherein the first ligand is or comprises a fatty acid.

46. The method of claim 45, wherein the fatty acid is a C2-C30 fatty acid.

47. The method of claim 46, wherein the is a C12-C20 fatty acid, optionally wherein the C12-C20 fatty acid is oleic acid.

48. The method of any one of claims 40 to 47, wherein a concentration of the QD in the mixture is between 1 and 100 mg / ml. [20mg / ml is the actual cone.]49. The method of any one of claims 40 to 48, wherein the ligand exchange comprises applying a solution of the second ligand to the at least one surface.

50. The method of any one of claims 40 to 49, wherein the second ligand is an aromatic compound.

51. The method of claim 50, wherein the aromatic compound is an amino phenyl.

52. The method of claim 50, wherein the amino phenyl is PDA.

53. The method of any one of claims 40 to 52, wherein the material is selected from glass, plastic and metal substrate.

54. The method of any one of claims 40 to 53, wherein the material is glass material, the glass material further comprises a coating comprising with a first layer comprising Indium tin oxide (ITO), or Fluorine doped tin oxide.

55. The method of claim 54, wherein the coating further comprises a second layer comprising TiO2, and wherein the second layer is in contact with the QD.

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