Fluorescent nanoparticles and preparation method thereof

Abstract

The present invention provides fluorescent nanoparticles comprising a zwitterionic complex comprising a cationically cross-linked polyethyleneimine and an anionic polymer comprising one or more repeating units represented by a moiety of Formula 1 wherein R1 is hydrogen or a C1-C3 alkyl group; and R2 is-CO2-or-CO2 (CH2) mCO2-, wherein m is an integer selected from 1 to 4. # imgabs0 #

Description

Technical Field

[0001] The present disclosure relates to fluorescent nanoparticles, methods for preparing the same, and uses thereof. Background Art

[0002] Over the past few decades, traditional organic fluorescent materials containing conjugated aromatic systems (such as fluorescent dyes, fluorescent proteins or conjugated polymers) have been widely used in various fields such as textile dyeing, lighting, bioimaging, medical diagnosis and anti-counterfeiting. However, these materials are affected by the aggregation-induced quenching (ACQ) effect when in the solid or aggregated state. This effect caused by the rigid π-conjugated structure of these materials limits their practical applications. To overcome this limitation, aggregation-induced emission molecules have emerged as an alternative to traditional organic dye molecules. AIE luminophores were first reported by Tang's team in 2001 and have attracted widespread attention due to their ability to emit light in the aggregated state. Unlike traditional fluorescent materials, AIE luminophores exhibit enhanced emission when aggregated, hence the name aggregation-induced emission (AIE) phenomenon. However, there are challenges associated with the use of AIE luminophores, including complex synthesis methods, high production costs and the lack of intrinsic photoluminescent properties of AIE molecules. In addition, many AIE-based photoluminescent materials can be "turned on and off" by controlling the aggregation state. This means that they do not emit light in dilute solutions and are generally considered not to be intrinsically photoluminescent.

[0003] Nanoparticles containing non-conjugated fluorescent polymers represent a new class of nanomaterials with good water dispersibility, biocompatibility, stability and low toxicity. These properties make them well-suited for a wide range of applications, including bioimaging, drug delivery, chemical detection, logic gates and temperature sensors. Typically, polymers containing heteroatoms with single bonds (e.g., NH, CO, CN) and double bonds (e.g., C=O, C=N, N=O) exhibit very weak fluorescence. However, their photoluminescence (PL) can be significantly enhanced by chemically or physically immobilizing them to restrict their vibrational and rotational relaxation.

[0004] An effective immobilization method is to utilize the cross-linking enhanced emission (CEE) effect, which covers various mechanisms such as supramolecular interaction CEE, ionic bonding CEE and confined CEE. Another strategy involves the clustering of electron-rich functional groups, and it is called cluster-induced emission (CTE). By confining the sub-fluorophores to a smaller volume, more efficient luminescence can be achieved through spatial conjugation (TSC) induced by the rigid conformation of the chromophore clusters. Utilizing the concepts of CEE and CTE, non-conjugated fluorescent nanoparticles have been prepared from precursor polymers or monomers by polymerization, cross-linking or self-assembly.

[0005] Polyethyleneimine (PEI) is a water-soluble polymer known for its high positive charge, which is derived from primary amine (-NH2) and secondary amine (-NH-) groups. These active amine groups allow PEI to be easily modified through various chemical reactions, thereby synthesizing a variety of PEI-based materials with a wide range of applications, such as pH sensing, bioimaging, gene delivery, drug delivery, antibacterial membranes, heavy metal ion removal, and CO2 adsorption. Branched PEI molecules have been reported to exhibit very weak blue fluorescence with a quantum yield (QY) of less than 1%. Several strategies to enhance PEI fluorescence have been reported. For example, Yang et al. cross-linked PEI with carbon tetrachloride (CTC), resulting in a QY of 2.7% when excited by 400nm light, and a maximum emission at 475nm. In another study, Liu et al. modified PEI with boric acid, resulting in a QY of 8.7% when excited by 380nm light, and a maximum emission at 500nm. In a recent study, Han et al. described the synthesis of green-emitting polymer dots by combining PEI with tetrakis(hydroxymethyl)phosphonium chloride (THPC). The resulting polymer dots exhibited a high quantum yield (QY) of 25% upon excitation at 400 nm, with maximum emission at 515 nm. However, these modified PEIs typically require high-energy excitation in the 360 ​​to 400 nm range to achieve the highest emission intensity.

[0006] Therefore, there is a need for improved PEI-based fluorescent materials that can address or overcome at least some of the above-mentioned shortcomings. Summary of the Invention

[0007] Here, we present a novel method for the synthesis of green fluorescent polymer nanoparticles via graft copolymerization. The process involves a two-step reaction: first, crosslinking of polyethyleneimine (PEI) with glutaraldehyde (GA) in ethanol, followed by in situ polymerization of acrylic acid-based monomers in aqueous medium (Scheme 1). The synthesis of fluorescent nanoparticles proceeds via in situ electrostatic recombination between the negatively charged polymer and the positively charged PEI, resulting in polyion-complexed nanoparticles. Among the various nanoparticles synthesized, glutaraldehyde-crosslinked PEI / poly(methacrylic acid) (gPEI / PMAA) nanoparticles exhibited the most desirable properties, including high monodispersity, an average diameter of 35 nm, excitation-dependent fluorescence, and an emission maximum at 527 nm upon excitation at 480 nm in aqueous dispersion. The quantum yield of gPEI / PMAA nanoparticles reached 23.6% (±1.2%), compared to rhodamine 6GI, a commonly used standard for quantum yield measurement. The new water-dispersible green fluorescent polymer nanoparticles have promising intrinsic photoluminescence properties and can be used as green fluorescent fillers in white light-emitting diodes (WLEDs) that utilize monochromatic blue LED chips as light sources.

[0008] In a first aspect, provided herein are fluorescent nanoparticles comprising a zwitterionic complex, wherein the zwitterionic complex comprises a cationic cross-linked polyethyleneimine and an anionic polymer comprising one or more repeating units represented by a moiety of Formula 1:

[0009]

[0010] where R 1 is hydrogen or C1-C3 alkyl; and R 2 Yes -CO2 - or -CO2(CH2) m CO2 - , wherein m is an integer selected from 1-4.

[0011] In certain embodiments, cationic cross-linked polyethyleneimine is prepared by reacting polyethyleneimine with a cross-linking agent selected from the group consisting of C2-C 18 Alkyl dialdehydes, The group composed of.

[0012] In certain embodiments, the polyethylenimine is reacted with CHO(CH2) n Cationic cross-linked polyethyleneimine is prepared by reacting CHO, wherein n is an integer selected from 2-10.

[0013] In certain embodiments, the cationic cross-linked polyethyleneimine is prepared by reacting polyethyleneimine with glutaraldehyde.

[0014] In certain embodiments, the cationic cross-linked polyethyleneimine is prepared by reacting a cross-linking agent with a polyethyleneimine selected from the group consisting of branched polyethyleneimine, linear polyethyleneimine, and mixtures thereof.

[0015] In certain embodiments, the polyethyleneimine has a weight average molecular weight of 1,000-1,000,000 kDa.

[0016] In certain embodiments, R 1 is hydrogen, methyl or ethyl; and R 2 Yes -CO2 - or -CO2(CH2) m CO2 - , wherein m is an integer selected from 1-2.

[0017] In certain embodiments, R 1 is hydrogen or methyl; and R 2 Yes -CO2 - or -CO2(CH2)2CO2- .

[0018] In certain embodiments, the anionic polymer comprises anionic poly(acrylic acid), anionic poly(methacrylic acid), anionic poly(2-carboxyethyl acrylate), or copolymers or mixtures thereof.

[0019] In certain embodiments, the C2-C 18 The invention relates to a method for preparing a cationic cross-linked polyethyleneimine by reacting an alkyl dialdehyde with polyethyleneimine, wherein the polyethyleneimine is selected from the group consisting of branched polyethyleneimine, linear polyethyleneimine and mixtures thereof, wherein the polyethyleneimine has a weight average molecular weight of 1,000-1,000,000 kDa; R 1 is hydrogen, methyl or ethyl; and R 2 Yes -CO2 - or -CO2(CH2) m CO2 - , wherein m is an integer selected from 1-2.

[0020] In certain embodiments, the cationic cross-linked polyethyleneimine is prepared by reacting glutaraldehyde with a branched polyethyleneimine, wherein the polyethyleneimine has a weight average molecular weight of 10,000-30,000 kDa; and the anionic polymer comprises anionic poly(acrylic acid), anionic poly(methacrylic acid), anionic poly(2-carboxyethyl acrylate), or a copolymer or mixture thereof.

[0021] In certain embodiments, the cationic cross-linked polyethyleneimine and the anionic polymer are present in the zwitterionic complex in a mass ratio of 1:1 to 1:4, respectively.

[0022] In certain embodiments, the cationic cross-linked polyethyleneimine is prepared by reacting glutaraldehyde with a branched polyethyleneimine, wherein the polyethyleneimine has a weight average molecular weight of 20,000-30,000 kDa; and the anionic polymer comprises anionic poly(acrylic acid), anionic poly(methacrylic acid), anionic poly(2-carboxyethyl acrylate), or a copolymer or mixture thereof.

[0023] In certain embodiments, the anionic polymer comprises anionic poly(methacrylic acid), and the cationic cross-linked polyethyleneimine and the anionic poly(methacrylic acid) are present in the zwitterionic complex in a mass ratio of 1:2 to 1:3, respectively.

[0024] In certain embodiments, glutaraldehyde and branched polyethyleneimine are reacted at a pH of about 3.

[0025] In a second aspect, provided herein is a method for preparing the fluorescent nanoparticles, the method comprising combining a cross-linked polyethyleneimine and at least one anionic polymer precursor to form a reaction mixture; and polymerizing the at least one anionic polymer precursor with a polymerization agent to form nanoparticles, wherein each of the at least one anionic polymer precursor independently has Formula 2:

[0026]

[0027] where R 1 is hydrogen or C1-C3 alkyl; and R 2 is -CO2H or -(CH2) m CO2H, wherein m is an integer selected from 1-4.

[0028] In certain embodiments, the polymerization agent comprises ultraviolet radiation, a free radical initiator, heat, or a combination thereof.

[0029] In certain embodiments, the free radical initiator is a peroxide.

[0030] In certain embodiments, the method further comprises combining the polyethyleneimine with a cross-linking agent selected from the group consisting of:

[0031] C2-C 18 Alkyl dialdehydes, Thereby, the cross-linked polyethyleneimine is formed.

[0032] In certain embodiments, polyethyleneimine and C2-C 18 The alkyl dialdehydes are combined at a pH of approximately 3. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above-mentioned aspects of the present invention and many of the attendant advantages will become more readily understood and appreciated by referring to the following detailed description taken in conjunction with the accompanying drawings.

[0034] Figure 1 Depicted is a scheme for an exemplary two-step synthesis of green fluorescent nanoparticles: Step 1) Crosslinking of PEI with 2 mol% glutaraldehyde in ethanol (EtOH) solution at room temperature for 24 hours. Step 2) Polymerization of anionic monomers (e.g., acrylic acid (AA), methacrylic acid (MAA), and 2-carboxyethyl acrylate (CEA)) to form poly-ion-complexed nanoparticles.

[0035] Figure 2 Depicted are A) images of gPEI / PMAA nanoparticles synthesized at pH 1, 3, 5, 7, and 9 under ambient light (upper panel) and 365 nm light (lower panel), B) maximum fluorescence intensity of gPEI / PMAA nanoparticles synthesized at different pH values ​​(1, 3, 5, 7, and 9).

[0036] Figure 3 Depicted are fluorescence intensity spectra of gPEI / PMAA nanoparticles synthesized at gPEI to MAA weight ratios of A) 1:1, B) 1:2, C) 1:3, D) 1:4, and E) comparison of fluorescence intensity of nanoparticles synthesized with MAA, AA, and CEA at different gPEI to monomer weight ratios.

[0037] Figure 4 Depicted are A) gPEI / PMAA nanoparticle size and size distribution; B) SEM images and size distribution of gPEI / PMAA nanoparticles; C) ζ-potential as a function of pH of gPEI / PMAA nanoparticles; and D) images of gPEI / PMAA nanoparticles (1,000 ppm) at different solution pH under ambient light (top) and 365 nm light (bottom). gPEI / PMAA nanoparticles were synthesized at a 1:2 (wt / wt) ratio of gPEI to MAA at pH 3.

[0038] Figure 5 A and B) UV / Vis absorption and fluorescence spectra of 25k PEI at a concentration of 100,000 ppm; C and D) UV / Vis absorption and fluorescence spectra of gPEI at a concentration of 1,000 ppm; E and F) UV / Vis absorption and fluorescence spectra of gPEI / PMAA nanoparticles at a concentration of 1,000 ppm.

[0039] Figure 6 Depicted are the spectra, CCT, CIE, D of LEDs coated with A) 0 wt% (control); B) 10 wt%; C) 20 wt% and D) 30 wt% of gPEI / PMAA nanoparticles. uv E) is the CIE of LED chips coated with A) 0 wt% (control); B) 10 wt%; C) 20 wt% and D) 30 wt% gPEI / PMAA nanoparticles. xy 1931 chromaticity diagram, with Planckian locus and correlated color temperature lines.

[0040] Figure 7 Depicted are the monomer conversions of MAA in the synthesis of gPEI / PMAA at a 1:2 (wt / wt) ratio of gPEI:MAA at pH=3.

[0041] Figure 8 Depicted are the size distributions of gPEI / PMAA nanoparticles synthesized with a 1:2 (wt / wt) ratio of gPEI:MAA at A) pH = 1, B) pH = 3, C) pH = 5, D) pH = 7, and E) pH = 9.

[0042] Figure 9 Depicted are the size distributions of gPEI / PMAA nanoparticles synthesized at gPEI:MAA weight ratios of A) 1:1, B) 1:2, C) 1:3, and D) 1:4 at pH=3.

[0043] Figure 10 Depicted are the particle size distributions of gPEI / PCEA nanoparticles synthesized at gPEI:CEA weight ratios of A) 1:1, B) 1:2, C) 1:3, and D) 1:4 at pH=3.

[0044] Figure 11 Depicted are the particle size distributions of gPEI / PAA nanoparticles synthesized at gPEI:AA weight ratios of A) 1:1, B) 1:2, C) 1:3, and D) 1:4 at pH=3.

[0045] Figure 12 Depicted are FTIR spectra of 25k branched PEI, GA, gPEI, PMAA, and gPEI / PMAA nanoparticles synthesized at a gPEI:PMAA weight ratio of 1:2 at pH=3.

[0046] Figure 13 Depicted are fluorescence spectra of gPEI / PMAA nanoparticles (1,000 ppm) synthesized with a 1:2 (wt / wt) gPEI:MAA at A) pH = 1, B) pH = 3, C) pH = 5, D) pH = 7, and E) pH = 9.

[0047] Figure 14 Depicted are fluorescence spectra of gPEI / PAA nanoparticles (1,000 ppm) synthesized at gPEI:AA weight ratios of A) 1:1, B) 1:2, C) 1:3, and D) 1:4 at pH=3.

[0048] Figure 15 Depicted are fluorescence spectra of gPEI / PCEA nanoparticles (1,000 ppm) synthesized at gPEI:CEA weight ratios of A) 1:1, B) 1:2, C) 1:3, and D) 1:4 at pH=3.

[0049] Figure 16 Plotted are integrated fluorescence intensity versus absorbance for quinine sulfate and gPEI.

[0050] Figure 17 Depicted are plots of integrated fluorescence intensity versus absorbance for Rhodamine 6G and gPEI / PMAA nanoparticles synthesized at a gPEI:PMAA weight ratio of 1:2 at pH=3.

[0051] Figure 18The CCT, CIE, and CIE values ​​of LED chips coated with 0 wt% (control), 10 wt%, 16 wt%, 20 wt%, and 30 wt% of gPEI / PMAA nanoparticles are depicted. xy 、D uv , CRI table.

[0052] Figure 19 Depicted are compounds studied for modification / crosslinking of PEI, and photographs of the corresponding modified / crosslinked PEI (1000 ppm in water) under a 365 nm UV lamp. Low fluorescence intensity was observed for PEI modified with EDTA ester and cyclohexane oxide. However, the remaining compounds containing at least two electrophilic moieties and capable of crosslinking PEI exhibited stronger fluorescence intensities, with Cy-PEI, cyclopentenone, and cyclohexenone exhibiting the highest fluorescence intensities, as shown in FIG. Figure 20 shown.

[0053] Figure 20 Depicted are the maximum λ values ​​of seven modified / cross-linked PEIs and native PEI. em For comparison, the parentheses show the λ of each modified PEI (1000 ppm) ex . DETAILED DESCRIPTION

[0054] definition

[0055] Throughout this disclosure, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of a specified integer or group of integers but not the exclusion of any other integer or group of integers. It should also be noted that in this disclosure, especially in the claims and / or paragraphs, terms such as "comprise," "comprising," "containing," etc., may mean "including," and terms such as "consisting essentially of" and "consisting essentially of" allow for elements not expressly recited but exclude elements found in the prior art or elements that affect the basic or novel characteristics of the invention.

[0056] Furthermore, throughout the present disclosure and claims, unless the context requires otherwise, the word "include" or variations such as "includes" or "including" will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0057] Unless otherwise expressly stated, nouns used herein include both the singular and the plural. In addition, unless otherwise expressly stated, when the term "about" is used before a quantitative value, the teachings of the present invention also include the specific quantitative value itself. As used herein, unless otherwise stated or inferred, the term "about" refers to a variation of ±10%, ±7%, ±5%, ±3%, ±1%, or ±0% relative to the stated value.

[0058] As used herein, a "polymeric compound" (or "polymer") refers to a molecule comprising a plurality of one or more repeating units connected by covalent chemical bonds. A polymeric compound can be represented by the general formula I:

[0059] *-(-(Ma) x —(Mb) y —) z *

[0060] Formula I

[0061] Wherein each Ma and Mb is a repeating unit or monomer. A polymeric compound may have only one type of repeating unit or may have two or more different repeating units. When a polymeric compound has only one type of repeating unit, it may be referred to as a homopolymer. When a polymeric compound has two or more types of different repeating units, the terms "copolymer" or "copolymeric compound" may be used instead. For example, a copolymeric compound may include repeating units, wherein Ma and Mb represent two different repeating units. Unless otherwise specified, the arrangement of repeating units in the copolymer may be head-to-tail, head-to-head, or tail-to-tail. In addition, unless otherwise specified, the copolymer may be a random copolymer, an alternating copolymer, or a block copolymer. For example, Formula I may be used to represent a copolymer of Ma and Mb, having an x ​​mole fraction of Ma and a y mole fraction of Mb in the copolymer, wherein the manner in which the comonomers Ma and Mb are repeated may be alternating, random, regio-random, regio-regular, or block, with up to z comonomers present. In addition to its composition, a polymeric compound can be further characterized by its degree of polymerization (n) and molar mass (e.g., number average molecular weight (M) and / or weight average molecular weight (Mw), depending on the measurement technique). The polymers described herein can exist in various stereochemical configurations, for example, in isotactic, syndiotactic, atactic, or combinations thereof.

[0062] The term "alkyl" is well known in the art and includes saturated aliphatic groups, including straight chain alkyl groups, branched chain alkyl groups, cycloalkyl (alicyclic) groups, alkyl-substituted cycloalkyl groups, and cycloalkyl-substituted alkyl groups. In certain embodiments, a straight chain or branched chain alkyl group has about 30 or fewer carbon atoms in its backbone (e.g., a straight chain is C1-C1 30 , the branched chain is C3-C 30), or about 20 or fewer carbon atoms. Likewise, cycloalkyl groups have from about 3 to about 10 carbon atoms in their ring structure, or about 5, 6, or 7 carbon atoms in their ring structure.

[0063] Provided herein are fluorescent nanoparticles comprising a zwitterionic complex, wherein the zwitterionic complex comprises a cationic cross-linked polyethyleneimine and an anionic polymer comprising one or more repeating units represented by a moiety of Formula 1:

[0064]

[0065] where R 1 is hydrogen or C1-C3 alkyl; and R 2 Yes -CO2 - or -CO2(CH2) m CO2 - , wherein m is an integer selected from 1-4.

[0066] The zwitterionic complex can comprise a plurality of basic residues, each of which can independently exist in a protonated form or as a free base, and a plurality of acidic residues, which can also independently exist in a protonated form as a conjugate base, and thus can exist in a variety of protonation / zwitterionic states. The present disclosure contemplates all such protonation / zwitterionic states. The protonation / zwitterionic state of the zwitterionic complex can depend on the pH of the composition containing the zwitterionic complex.

[0067] The further repeating unit may be the same or different. Where the anionic polymer comprises different repeating units, the anionic polymer may comprise 2, 3, 4, 5, 6, 7, 8, 9, 10 or more different repeating units.

[0068] R 1 Can be hydrogen, methyl, ethyl, n-propyl or isopropyl. In certain embodiments, R 1 is hydrogen or methyl.

[0069] R 2 It can be -CO2 - or -CO2(CH2) m CO2 - , wherein m is 1-4, 1-3 or 1-2. In certain embodiments, R 2 It is CO2 - or -CO2(CH2)2CO2 - It should be understood that, due to the characteristics of acid-base chemistry, the presence of -CO2 in each repeating unit - or -CO2(CH2) m CO2 -May exist independently in a protonated state (ie, as a conjugate acid). However, the net negative charge of the anionic polymer should be at least -1 or greater.

[0070] In certain embodiments, the anionic polymer comprises one or more repeating units selected from the group consisting of the following repeating units, wherein R 1 is hydrogen and R 2 It is CO2 - , R 1 is methyl and R 2 It is CO2 - , R 1 is hydrogen and R 2 It is -CO2(CH2)2CO2 - In certain embodiments, the anionic polymer comprises anionic poly(acrylic acid), anionic poly(methacrylic acid), anionic poly(2-carboxyethyl acrylate), or copolymers or mixtures thereof.

[0071] Cationic cross-linked polyethyleneimine can be prepared by reacting polyethyleneimine with a cross-linking agent.

[0072] The polyethyleneimine can be a branched polyethyleneimine, a linear polyethyleneimine, a cyclic polyethyleneimine, or a combination or mixture thereof. In certain embodiments, the polyethyleneimine is a branched polyethyleneimine. The weight average molecular weight of the polyethyleneimine can be 1,000-100,000 kDa, 1,000-90,000 kDa, 1,000-80,000 kDa, 1,000-70,000 kDa, 1,000-60,000 kDa, 1,000-50,000 kDa, 1,000-40,000 kDa, 1,000-30,000 kDa, 5,000-30,000 kDa, 10,000-30,000 kDa, 15,000-30,000 kDa, 20,000-30,000 kDa, 25,000-30,000 kDa, or 20,000-25,000 kDa. In certain embodiments, the polyethyleneimine has a weight average molecular weight of about 25,000 kDa.

[0073] There are no particular limitations on the crosslinking agent and it can be any crosslinking agent comprising two, three, four, five or more electrophilic species capable of reacting with the nucleophile present in the polyethyleneimine. In certain embodiments, the crosslinking agent comprises two or more electrophilic species selected from the group consisting of carbonyl, epoxide, isocyanate, vinyl ketone and vinyl aldehyde. In certain embodiments, the crosslinking agent is a linear or branched C2-C 18 Alkyl dialdehyde, C2-C 17 Alkyl dialdehyde, C2-C 16 Alkyl dialdehyde, C2-C15 Alkyl dialdehyde, C2-C 14 Alkyl dialdehyde, C2-C 13 Alkyl dialdehyde, C2-C 12 Alkyl dialdehyde, C2-C 11 Alkyl dialdehyde, C2-C 10 alkyl dialdehyde, C2-C9 alkyl dialdehyde, C2-C8 alkyl dialdehyde, C2-C7 alkyl dialdehyde, C2-C6 alkyl dialdehyde, C2-C5 alkyl dialdehyde, C2-C4 alkyl dialdehyde or C2-C3 alkyl dialdehyde. Exemplary alkyl dialdehydes include, but are not limited to, adipaldehyde (C6), glutaraldehyde (C5), succinaldehyde (C4), malondialdehyde (C3) and glyoxal (C2). In certain embodiments, the cross-linking agent is glutaraldehyde. Figure 19 As shown, other crosslinkers can be used to prepare crosslinked fluorescent PEI. Such crosslinkers include:

[0074]

[0075] The average particle size of the fluorescent nanoparticles can be 10-500nm, 10-400nm, 10-300nm, 10-200nm, 10-100nm, 10-90nm, 10-80nm, 10-70nm, 10-65nm, 10-60nm, 5-65nm, 10-50nm, 10-40nm, 20-50nm, 20-40nm, 30-40nm, 32-38nm, 32-36nm, 33-36nm, 34-36nm or 34-35nm. In certain embodiments, the average particle size of the fluorescent nanoparticles is about 34.6nm.

[0076] Under the excitation wavelength between 400-480nm, 420-480nm, 440-480nm or 460-480nm, fluorescent nanoparticles can show the emission maximum of fluorescence between 480-527nm, 490-527nm, 500-527nm, 510-527nm or 520-527nm. Advantageously, the fluorescent nanoparticles comprising zwitterionic complex show a quantum yield significantly higher than corresponding cross-linked polyethyleneimine. In certain embodiments, the quantum yield of fluorescent nanoparticles is about 23.5%. Because fluorescent nanoparticles as herein described can use less energetic light excitation (for example, within the scope of 400-480nm, 420-480nm, 440-480nm or 460-480nm) to realize maximum emission intensity, they can be used as the fluorescent material in biological system, if otherwise, biological system can be used to excite the higher energy light (for example, <400nm) required for known fluorescent material based on PEI and damage.

[0077] The fluorescent nanoparticles described herein can be readily prepared using methods well known in the art. In certain embodiments, the fluorescent nanoparticles are prepared by combining a cross-linked polyethyleneimine and at least one anionic polymer precursor to form a reaction mixture; and polymerizing the at least one anionic polymer precursor with a polymerization agent to form nanoparticles, wherein each of the at least one anionic polymer precursor independently has Formula 2:

[0078]

[0079] where R 1 is hydrogen or C1-C3 alkyl; and R 2 is -CO2H or -(CH2) m CO2H, wherein m is an integer selected from 1-4.

[0080] The at least one anionic polymer precursor can be the same or different.In certain embodiments, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more anionic polymer precursors are combined with a crosslinked polyethyleneimine.

[0081] The cross-linked polyethyleneimine and the more anionic polymer precursor can be combined in a mass ratio of 1:9 to 9:1, 1:4 to 4:1, 3:7 to 7:3, 2:3 to 3:2, 1:1 to 1:4, 1:2 to 1:4, 1:2 to 1:3, or 1:3 to 1:4, respectively. Unexpectedly, it was found that when the cross-linked polyethyleneimine and methacrylic acid were combined in a mass ratio of 1:2 to 1:3 or about 1:3, respectively, the fluorescence intensity of the fluorescent nanoparticles was the highest.

[0082] The step of crosslinked polyethyleneimine and at least one anionic polymer precursor combination and polymerization at least one anionic polymer precursor can be carried out independently of one another under pure state or in solvent.The suitable solvent for combining crosslinked polyethyleneimine and at least one anionic polymer precursor and polymerization can be any solvent that crosslinked polyethyleneimine and at least one anionic polymer precursor are at least partially soluble therein.In certain embodiments, the solvent for combining step and polymerization step comprises polar protic solvent or aprotic solvent, for example water, alcohol, ether, alkyl halide, ether, ester, ketone, methane amide, alkyl nitrile, alkyl sulfoxide and mixture thereof.The exemplary solvent that can be used for crosslinking reaction includes but not limited to water, methanol, ethanol, 1-propyl alcohol, 2-propyl alcohol, ethylene glycol, tetrahydrofuran (THF), tetrahydropyran, dioxane and mixture thereof.In certain embodiments, the solvent for combining and polymerization step independently comprises water, ethanol or its mixture.

[0083] The polymerization agent can be any compound or method that can be used to polymerize acrylic acid-based monomers. The selection of a suitable polymerization agent is within the skill of those of ordinary skill in the art. In certain embodiments, the polymerization agent comprises ultraviolet radiation, a free radical initiator, heat, or a combination thereof. The free radical initiator can comprise an organic peroxide, an inorganic peroxide, an azoalkane, or a metal. Exemplary free radical initiators include, but are not limited to, hydrogen peroxide, hypochlorous acid, di-tert-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α,α-bis(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, benzoyl peroxide, lauroyl peroxide, dilauroyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, azobisisobutyronitrile (AIBN), 1,1′-azobis(cyclohexanecarbonitrile) (ABCN), potassium persulfate, iron sulfate, and combinations thereof. In certain embodiments, the free radical initiator comprises hydrogen peroxide.

[0084] In certain embodiments, the method further comprises the step of cross-linking the polyethyleneimine with a cross-linking agent. The polyethyleneimine can be any polyethyleneimine disclosed in any embodiment herein. The cross-linking agent can be any cross-linking agent disclosed in any embodiment herein. The cross-linking reaction can be carried out in any solvent in which the polyethyleneimine and the cross-linking agent are at least partially dissolved. In certain embodiments, the solvent for the cross-linking reaction comprises a polar protic solvent or an aprotic solvent, such as water, alcohol, ether, alkyl halide, ether, ester, ketone, formamide, alkyl nitrile, alkyl sulfoxide and mixtures thereof. Exemplary solvents that can be used for the cross-linking reaction include, but are not limited to, water, methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, tetrahydrofuran, tetrahydropyran, dioxane and mixtures thereof. In certain embodiments, the solvent for the cross-linking reaction comprises ethanol or a mixture thereof.

[0085] As discussed below, the pH of the crosslinking reaction can affect the properties of the fluorescent nanoparticles described herein. It was unexpectedly discovered that, while the pH of the crosslinking reaction can range from 1 to 9, the fluorescent nanoparticles exhibited the highest fluorescence intensity when crosslinked with polyethyleneimine and an alkyl dialdehyde crosslinker at a pH of 1 to 5, 2 to 5, 2 to 4, 2.5 to 3.5, 2.75 to 3.25, or about 3.

[0086] The cross-linking agent can be combined with polyethyleneimine at 0.1-25 mol%, 0.1-20 mol%, 0.1-15 mol%, 0.1-10 mol%, 1-10 mol%, 1-9 mol%, 1-8 mol%, 1-6 mol%, 1-5 mol%, 1-3 mol%, 2-3 mol%, 1.5-2.5 mol%, or 1.75-2.25 mol%. In certain embodiments, the cross-linking agent is combined with polyethyleneimine at about 2 mol%.

[0087] The cross-linking reaction can be carried out at 20-60° C., 20-50° C., 20-40° C., 20-30° C., or 20-25° C. In certain embodiments, the cross-linking reaction is carried out at about 23° C.

[0088] The present disclosure also provides a white light emitting diode (LED), comprising an LED having an emission wavelength in the range of 400-480 nm, 420-480 nm, 440-480 nm, or 460-480 nm, and a phosphor layer comprising the fluorescent nanoparticles described herein, wherein the phosphor layer is disposed on a surface of the LED such that light emitted by the LED passes through the phosphor. In certain embodiments, the LED is a violet LED, an indigo LED, or a blue LED.

[0089] Synthesis of gPEI / PMAA Polymeric Ionic Composite Nanoparticles

[0090] The synthesis of green fluorescent nanoparticles containing glutaraldehyde-crosslinked polyethyleneimine (gPEI) and poly(methacrylic acid) (PMAA) was carried out in two stages, as Figure 1 As shown. In the first stage, PEI is cross-linked with 2mol% glutaraldehyde in an ethanol (EtOH) solution at room temperature for 0.5-24 hours. The reaction involves a reaction between the aldehyde group of PEI rich in amine and glutaraldehyde, resulting in the formation of an imine bond. After removing EtOH from the EtOH / water mixture, a pale yellow gPEI aqueous solution is obtained. The influence of the degree of cross-linking is studied by changing the molar percentage of glutaraldehyde and PEI within the range of 2mol%, 3mol%, 4mol% and 6mol%. Precipitation is observed when the glutaraldehyde concentration exceeds 3mol%. Therefore, the subsequent reaction selects a reaction cross-linked using 2mol% glutaraldehyde.

[0091] In the second stage of the synthesis, anionic monomers containing carboxylic acid groups, such as acrylic acid (AA), methacrylic acid (MAA), and 2-carboxyethyl acrylate (CEA), are polymerized in situ to form poly-ion-complexed nanoparticles. The electrostatic interaction between the amine groups in PEI and the carboxylic acid groups in the growing polymer leads to the formation of these nanoparticles.

[0092] Effect of reaction conditions on the synthesis of gPEI / PMAA nanoparticles

[0093] Before investigating the effect of monomer structure on the properties of fluorescent nanoparticles, a gPEI to MAA weight ratio of 1:2 was used to study the effects of reaction time and pH on MAA polymerization. Figure 7 The results shown show that monomer conversion gradually increases with increasing reaction time, reaching approximately 80% conversion after three hours. Further extending the reaction time from 3 hours to 4.5 hours did not bring any significant changes in monomer conversion. Therefore, the optimal reaction time for the synthesis of gPEI / PMAA nanoparticles was determined to be 3 hours.

[0094] PEI is a cationic polymer that is pH-sensitive due to the presence of amine groups. In an acidic environment, the amine groups are protonated, resulting in a positive charge. Therefore, the effect of solution pH on the synthesis and photoluminescence properties of PEI-based nanoparticles was investigated at pH 1, 3, 5, 7, and 9. Figure 8 The results shown indicate that the nanoparticles synthesized at pH 3 and 5 exhibited a narrow size distribution, while the nanoparticles synthesized at pH 1, 7, and 9 exhibited a multimodal size distribution. The average particle sizes obtained at pH 3 and 5 were approximately 35 nm and 38 nm, respectively.

[0095] To examine the effect of pH on the photoluminescence properties of gPEI / PMAA nanoparticles, the fluorescence intensity was measured using a spectrofluorometer. Figure 2 The results revealed that gPEI / PMAA nanoparticles synthesized at pH 3 exhibited the highest fluorescence intensity. In addition, the maximum excitation and emission wavelengths were 480 nm and 527 nm, respectively, indicating the green fluorescence properties of these nanoparticles.

[0096] Influence of monomer structure

[0097] In the second stage of the synthesis, anionic monomers containing carboxylic acid groups were investigated, including acrylic acid (AA), methacrylic acid (MAA), and 2-carboxyethyl acrylate (CEA). Polymerization was initiated with H2O2 at 80°C and pH 3. The resulting polymer consists of negatively charged chains that can electrostatically interact with the amine groups in PEI to form polyionic nanoparticles. As a result, the nanoparticles have positively charged polymer chains (the amine groups in PEI) and negatively charged polymer chains (the carboxylic acid groups), giving them zwitterionic properties.

[0098] To investigate the effect of the weight ratio between gPEI and acrylic acid-based monomers, weight ratios of 1:1, 1:2, 1:3, and 1:4 were tested. When MAA was polymerized, highly monodispersed nanoparticles were obtained with gPEI and MAA at weight ratios of 1:2 and 1:3, with average particle sizes of 35 nm and 47 nm, respectively. Figure 9 When CEA was polymerized, unimodal distributions of gPEI / PCEA nanoparticles were also obtained at weight ratios of gPEI to CEA of 1:2 and 1:3. However, the average particle sizes of these ratios were significantly larger compared to gPEI / PMAA nanoparticles, measured at 178 nm and 258 nm, respectively ( Figure 10 In the case of graft polymerization of AA onto gPEI, a multimodal particle size distribution of gPEI / PAA nanoparticles was observed at all weight ratios ( Figure 11 Based on these findings, it can be concluded that polymerization of MAA in the presence of gPEI at a weight ratio of 2:1 will produce the smallest nanoparticles with a narrow size distribution.

[0099] The fluorescence intensity of gPEI / PMAA, gPEI / PAA and gPEI / PCEA nanoparticles was measured and compared. The results showed that gPEI / PMAA nanoparticles synthesized with a weight ratio of gPEI to MAA of 1:2 showed the highest fluorescence intensity ( Figure 3 E). One possible explanation for the observed change in fluorescence intensity is related to the structural rigidity of the polymer. Due to the presence of methyl side groups on the polymer backbone, poly(methacrylic acid) (PMAA) has a more rigid structure than polyacrylic acid (PAA). The increased rigidity of PMAA leads to a higher degree of confinement of the polyion complexes formed within the nanoparticles, thereby enhancing the fluorescence intensity. On the other hand, poly(2-carboxyethyl acrylate) contains flexible -CH2-CH2- side groups, which provide more free volume within the polymer structure. Therefore, the degree of confinement of the polyion complexes is lower, resulting in weaker fluorescence intensity. Therefore, polymers with higher backbone rigidity (such as PMAA) impose greater restrictions on the movement of the polymer chain. This enhanced confinement promotes stronger electronic interactions between subfluorophores (CO, CN, C=O, C=N) within the nanoparticles, resulting in more efficient radiation attenuation and thus higher fluorescence intensity.

[0100] Characteristics of gPEI / PMAA nanoparticles

[0101] The chemical structures of native PEI, GA, gPEI, PMAA, and gPEI / PMAA were analyzed using Fourier transform infrared (FTIR) spectroscopy. Figure 12 ). The characteristic peak of PEI appears at about 3400 cm -1 (NH expansion), 1645cm-1 (Primary NH bend), 1568cm -1 (Secondary NH bend), 1470cm -1 (-CH2- stretching) and 1312cm -1 (CN stretching). The spectrum of GA is at 1718cm -1 When the spectrum of gPEI is compared with that of PEI and GA, the peak at 1645 cm-1 of PEI is still observed. -1 and 1560cm -1 The -NH2 and -NH- peaks at 1645 cm correspond to the C=N group. -1 The absorption at 2500-3500 cm-1 increased, indicating the formation of a Schiff base due to the reaction between GA and the primary amine groups of PEI. -1 Broad peaks in the range of 1700 cm-1 correspond to OH and NH stretching. -1 The C=O stretching peak at 1172 cm -1 The CO stretching peak at π indicates the presence of PMAA polymer. FTIR spectroscopy confirmed the chemical composition of the nanoparticles, which contained glutaraldehyde-crosslinked PEI and PMAA polymer.

[0102] The morphology of gPEI / PMAA nanoparticles synthesized under the optimal conditions (gPEI:MMA=1:2w / w, pH=3, 3h) was examined using scanning electron microscopy (SEM). Figure 4 As shown in Figure 2, most nanoparticles are spherical with diameters ranging from 5 nm to 68 nm. DLS measurements showed that the average diameter of the nanoparticles was 35 nm and the PDI value was 0.29 ( Figure 4 A).

[0103] Due to the presence of opposite charges, the combination of gPEI and PMAA polymers via in situ polymerization resulted in the formation of zwitterionic gPEI / PMAA composite nanoparticles. Figure 4 Figure C clearly demonstrates the zwitterionic nature of the nanoparticles, which plots the ζ-potential as a function of pH. The isoelectric point of the gPEI / PMAA nanoparticles was found to occur at pH = 6. The nanoparticles were observed to become unstable around this pH value, leading to nanoparticle aggregation, as shown in Figure 5. Figure 4 D. However, the nanoparticles showed stability when the solution pH level was lower than 4 or higher than 9. This indicates that gPEI / PMAA nanoparticles can maintain their dispersion and stability in either acidic or alkaline environments, while aggregation occurs under neutral pH conditions close to the isoelectric point.

[0104] The absorption characteristics of native PEI, GA-modified PEI, and gPEI / PMAA nanoparticles were analyzed using UV-Vis spectroscopy. For native PEI dissolved in water, only a weak absorption signal between 250 and 320 nm was observed even at a concentration of up to 10 wt %. Figure 5 A). After PEI was modified with GA, the resulting polymer showed a clear absorption peak at 420 nm ( Figure 5 C). This absorption peak can be attributed to the formation of imine bonds, which are formed by the reaction between the primary amine groups of PEI and the aldehyde groups of GA. The resulting gPEI / PMAA composite nanoparticles showed two absorption peaks at 326 and 475 nm ( Figure 5 E) These absorption peaks indicate that the nanoparticles have unique optical properties due to the formation of poly-ion complexes.

[0105] The fluorescence properties of natural PEI, GA-modified PEI, and gPEI / PMAA nanoparticles were studied using fluorescence spectroscopy. When excited by 360 nm light, natural PEI exhibited weak fluorescence with a maximum emission at 469 nm ( Figure 5 B). It is worth noting that the fluorescence intensity of native PEI shows dependence on the excitation wavelength. After PEI is cross-linked with GA, the fluorescence intensity of PEI is significantly enhanced, and the color of the solution changes from colorless to light yellow ( Figure 5 D). This observation is consistent with theory, indicating that GA modification alters the electronic structure of PEI, leading to an increase in fluorescence intensity. GA-modified PEI also exhibits excitation-dependent fluorescence properties. When excited by 400nm light, gPEI emits maximum light intensity at a wavelength of 502nm. This indicates that GA modification of PEI causes the maximum emission wavelength to red-shift from 469nm to 502nm when PEI is excited at 360nm and 400nm, respectively.

[0106] Figure 5Figure F shows the fluorescence spectrum of gPEI / PMAA nanoparticles. When excited at 460nm, 480nm and 500nm wavelengths, these nanoparticles exhibit strong green fluorescence emission within the range of 520nm to 530nm. Compared with gPEI, the excitation and emission maxima of gPEI / PMAA nanoparticles are further red-shifted to 480nm and 527nm, respectively. In addition, by fluorescence spectroscopy, the maximum fluorescence intensity of gPEI / PMAA nanoparticles is ten times higher than the maximum fluorescence intensity of gPEI. The red shift of the excitation and emission maxima of gPEI / PMAA nanoparticles can be attributed to the presence of PMAA, which may enhance the π electron system in the nanoparticles, resulting in displacement to longer wavelengths. Overall, compared with gPEI, the red-shifted excitation and emission maxima observed in gPEI / PMAA nanoparticles can be attributed to the influence of PMAA on electronic structure, molecular interaction and energy state in the nanoparticle system.

[0107] The photoluminescence properties of gPEI / PMAA nanoparticles were also characterized by measuring the relative quantum yield (QY) using quinine sulfate and rhodamine 6G as reference standards. It has been previously reported in the literature that native branched PEI exhibits very low QY, less than 1%. In the example, after PEI was modified with GA, the relative QY increased to 5.39% (± 0.38%). This shows that the fluorescence intensity of GA-modified gPEI is significantly enhanced compared to native PEI. In addition, the relative QY of gPEI / PMAA nanoparticles is further increased to 23.5% (± 1.2%). The significant increase in quantum yield indicates that the fluorescence intensity of gPEI / PMAA nanoparticles is significantly increased compared to native PEI and GA-modified gPEI.

[0108] The increased quantum yield and enhanced fluorescence properties of gPEI / PMAA nanoparticles suggest that PMAA incorporation and nanoparticle formation play a crucial role in the luminescence properties of gPEI / PMAA nanoparticles. Incorporation of PMAA into the gPEI system introduces negatively charged segments that can electrostatically interact with the positively charged gPEI segments. This leads to the formation of polyionic nanoparticles, in which the gPEI and PMAA chains are entangled and stabilized by electrostatic attraction. The formation of these polyionic complexes and the confinement within the nanoparticle structure can limit the vibrational and rotational relaxation of the polymer chains.

[0109] The confinement and close arrangement of subfluorophores of nanoscale size can lead to a phenomenon known as spatial conjugation of chromophore clusters. Spatial conjugation refers to the interaction between adjacent chromophores through non-covalent interactions without direct bonding. In the case of gPEI / PMAA nanoparticles, subfluorophores (such as CO, CN, C=O and C=N bonds) are confined within the nanoparticle structure and are in close proximity to each other. This close arrangement enables efficient energy transfer between subfluorophores, thereby enhancing luminescence. Overall, the presence of heteroatom bonds, the formation of polyionic complexes and the confinement of subfluorophores within the nanoscale size of gPEI / PMAA nanoparticles contribute to the spatial conjugation of chromophore clusters, thereby achieving efficient energy transfer and enhancing the photoluminescence properties of nanoparticles.

[0110] gPEI / PMAA nanoparticles as phosphors for WLEDs

[0111] One method for manufacturing white light-emitting diode (LED) chips involves integrating blue and green light sources to achieve the desired color temperature. This is called a phosphor-converted LED. Blue light excites a phosphor powder, which is typically encapsulated within a housing. Light emitted by the yellow phosphor combines with the blue light emitted by the LED to produce white light. The potential of gPEI / PMAA nanoparticles, which emit green light at a wavelength of 528 nm, is applied to generate white light LEDs using a monochromatic blue light source. This method offers the advantage of simplifying the design of LED lighting systems by combining the blue light emitted by the LED chip with the green light emitted by the nanoparticles embedded in the silicon housing.

[0112] Figure 6 and Figure 18 The optical properties of LED chips coated with different weight percentages of nanoparticles (10wt%, 20wt% and 30wt%) are shown. The CCT values ​​of LEDs with 10wt% and 20wt% coating are in the warm white to natural white range of 3648K and 5269K, respectively. However, the CCT value of the LED coated with 30wt% nanoparticles is 1877K, which is outside the white light range. In addition, the D uv The values ​​are all less than 0.02. This indicates that the light emitted by the LEDs is within the white region of the CIE 1931XYZ color space defined by the International Commission on Illumination. Furthermore, the color rendering index (CRI) values ​​of these white LEDs all exceed 80Ra, meaning that these LEDs can be classified as good chips in terms of color rendering quality.

[0113] Using gPEI / PMAA nanoparticles for white LEDs offers several advantages over other materials: 1) Tunable Color Properties: gPEI / PMAA nanoparticles enable the production of white LEDs with desired and adjustable colors. By varying the weight percentage, the CCT and CRI of the LEDs can be tailored to specific requirements. This flexibility in color control is advantageous for a variety of lighting applications requiring specific color temperatures or color rendering characteristics. 2) Simplified Design: gPEI / PMAA nanoparticles are integrated as a yellow-green phosphor activated by monochromatic blue light, simplifying the design of LED lighting systems. The blue light emitted by the LED chip is combined with the yellow-green light emitted by the nanoparticles, eliminating the need for complex color mixing mechanisms or multiple light sources. This simplification can save costs and streamline the production process. 3) Compatibility with Silicone Housings: gPEI / PMAA nanoparticles can be embedded in silicone housings, a material commonly used in LED manufacturing. This compatibility ensures good adhesion and stability of the nanoparticles within the LED structure, thereby improving the performance and lifetime of white LEDs. These advantages make fluorescent gPEI / PMAA nanoparticles promising materials for generating white-light LEDs with the advantages of versatility, simplified design, and high-quality light output.

[0114] We have developed a method for synthesizing nonconjugated green fluorescent nanoparticles in aqueous media. The synthesis involves two main steps: crosslinking of polyethyleneimine with glutaraldehyde in ethanol, followed by in situ polymerization of acrylic acid-based monomers. The combination of crosslinked PEI and polymerized acrylic acid-based monomers forms polyion-complexed nanoparticles. Scanning electron microscopy (SEM) analysis revealed the spherical morphology of the gPEI / PMAA nanoparticles, and zeta potential measurements provided insights into their zwitterionic nature and pH-dependent stability. Under excitation at wavelengths of 460 nm, 480 nm, and 500 nm, the glutaraldehyde-crosslinked PEI / poly(methacrylic acid) (gPEI / PMAA) nanoparticles exhibited robust green fluorescence emission in the 520-530 nm range, with a high quantum yield of up to 23.5%. This green fluorescence capability has been effectively utilized as a green light source in LED fabrication. Nonconjugated gPEI / PMAA nanoparticles with unique green fluorescence properties offer great potential for a variety of applications, including light-emitting diodes, optoelectronic devices, bioimaging, and fluorescence-based sensing systems.

[0115] experiment

[0116] Material

[0117] Branched polyethyleneimine [PEI, number average molecular weight (M n )≈10kDa, weight average molecular weight (M w)≈25 kDa] and glutaraldehyde (GA, 50 wt% in H2O) were obtained from Sigma Aldrich and used as received. Methacrylic acid (MAA), acrylic acid (AA), and 2-carboxyethyl acrylate (CEA) were also obtained from Sigma Aldrich and purified using a column packed with inhibitor remover (Sigma Aldrich). Hydrogen peroxide (H2O2, 35 wt% in water, Riedel-de ) was diluted to a concentration of 100 mM and stored at 4°C. Purification was performed using cellulose dialysis tubing with a molecular weight cutoff of 12,400 Da (Sigma Aldrich). Anhydrous ethanol (GR grade) was obtained from DUKS. Milli-Q water (H2O) was used as the dispersion medium. Silicone (ZWL8820, containing components A and B) was purchased from Shenzhen Zhanwanglong Technology Co., Ltd. (China).

[0118] Example 1 - Synthesis of cross-linked polyethyleneimine (gPEI) using glutaraldehyde

[0119] In a typical 200g batch, a mixture of 10g branched polyethyleneimine (PEI) dissolved in 90g ethanol (EtOH) was added dropwise to 0.945g glutaraldehyde (GA, 50wt% in H2O) dissolved in 99.055g EtOH and then stirred at room temperature for 24 hours. The color of the resulting solution was changed from clear to light yellow. Subsequently, the mixture was mixed with 200g water and EtOH was removed on a rotary evaporator. The aqueous solution was then dialyzed through Milli-Q water to purify the solution until the conductivity of the dialyzed solution dropped to a threshold value below 30μS / cm.

[0120] Example 2 - Synthesis of Polymeric Ion Composite Nanoparticles

[0121] The total weight of the preparation is 42.39g, and the concentration is that the glutaraldehyde cross-linked polyethyleneimine (gPEI) solution of 2.36wt% is mixed with the monomer (scope is 1g to 4g) of purification. Then, the pH of the mixture is adjusted to pH value 1, 3, 5, 7 or 9 using 2M HCl or 2M NaOH, and diluted with water to a final weight of 99g. The resulting mixture is transferred to a double-layer flask reactor equipped with a magnetic stirrer, a nitrogen inlet, a thermometer and a condenser. The mixture is stirred at room temperature for 10 minutes at a speed of 450rpm under N2, then heated to 80°C. By adding 1mL of 100mM H2O2, polymerization is initiated, and the reaction is carried out for 3 hours. In the reaction process, the solution becomes a brown turbid dispersion from a clear light yellow solution. Subsequently, the crude product is dialyzed by Milli-Q water until the conductivity of the dialyzed solution is reduced to less than 30μS / cm.

[0122] Example 3 - Measurement and Characterization

[0123] The spectral range was 500–4000 cm-1 on a Nicolet iS50 FT-IR spectrometer using a KBr disk. -1 Record Fourier transform infrared (FTIR) spectrum. Use Malvern Zetasizer Nano ZS to measure particle size and particle size distribution by dynamic light scattering (DLS). The Malvern Zetasizer Nano ZS is equipped with a photon correlation spectroscopy with electrophoretic dynamic light scattering and a dual laser diode light source with a wavelength of 632.8 nm at 4 mW and operates at a detector angle of 173 °. For particle size measurement, the sample is diluted to 1000 ppm in an aqueous solution, and for ζ-potential measurement, the sample is diluted to 1000 ppm in a 1 mM NaCl solution. The result of particle size and ζ-potential is the average value of three repeated measurements. Field emission scanning electron microscopy (FE-SEM, TESCAN MAIA3) is used to examine the morphology of nanoparticles. For sample preparation, an ion sputter coater (SEC, MCM-200) is used to coat a thin layer of gold on a P-type silicon chip substrate (SPI, 4136SC-AB). UV-Vis spectrometer (Agilent Technology Cary 8454) is used to obtain UV-visible light spectrum, covering the range of 200nm to 800nm. Samples are diluted to a concentration of 1000ppm with Milli-Q water before measurement. Fluorescence spectra are obtained using a fluorescence spectrophotometer (Horiba FluoroMax-4), with an excitation wavelength range of 300nm to 500nm, and a fixed increment of 20nm. The quantum yield (QY) of gPEI and gPEI / PMAA nanoparticles is measured using the relative quantum yield method. Quinine sulfate and rhodamine 6G are selected as reference standards, and the excitation wavelengths are 360nm and 480nm, respectively. At least five sample solutions or dispersions are prepared by diluting with Milli-Q water to obtain an absorbance of 0.01au to 0.1au at each excitation wavelength. Quinine sulfate and rhodamine 6G were diluted in 0.5 M H2SO4 solution and anhydrous ethanol, respectively, to obtain absorbances in the range of 0.01 au to 0.1 au at their respective excitation wavelengths. The fluorescence emission spectra of the prepared solutions or dispersions were measured by a fluorescence spectrophotometer. Then, the quantum yield QY of the sample was calculated by equation (1): x :

[0124] Among them, QY s is the quantum yield of the standard, A x and A s are the absorbance of the sample and the standard, respectively, and F x and Fs are the integrated fluorescence intensities of the sample and standard, n x and n s are the reflectance indices of the sample and standard, and m x and m s are the slopes of the integrated fluorescence intensity versus absorbance plots for samples and standards, respectively.

[0125] Example 4 - Fabrication of White Light Emitting Diodes (WLEDs)

[0126] Use vacuum freeze dryer (LABFREEZ, FD-10-R) to prepare the dry powder of gPEI / PMAA nanoparticles.Different amounts of nanoparticles (10wt%, 16wt%, 20wt% and 30wt% of the total amount of organosilicon) are fully mixed with organosilicon component B, and then mixed with organosilicon component A at room temperature.The mixing ratio of component A and component B is according to the 1:4 (wt / wt) recommended by the supplier.The gained mixture is vacuum degassed at room temperature for 30 minutes, and then 5mg of the mixture is applied to the 365nm LED chip.Then the sample is cured at 60 ℃ for 40 minutes, and then heated in an oven at 135 ℃ for 110 minutes.

[0127] The coated LED chips were connected to a power supply with a current of 120 mA (Major Science MP-250N), and a photodetector (AsenseTek Lighting passport, ALP-01, Taiwan, China) was used to measure the correlated color temperature (CCT), color rendering index (CRI), and deep ultraviolet (Duv) light.

Claims

1. Fluorescent nanoparticles comprising a zwitterionic complex, wherein the zwitterionic complex comprises a cationic cross-linked polyethyleneimine and an anionic polymer comprising one or more repeating units represented by a moiety of Formula 1: where R 1 is hydrogen or C1-C3 alkyl; and R 2 Yes -CO2 - or -CO2(CH2) m CO2 - , wherein m is an integer selected from 1-4.

2. The fluorescent nanoparticles according to claim 1, wherein the cationic cross-linked polyethyleneimine is prepared by reacting polyethyleneimine with a cross-linking agent, wherein the cross-linking agent is selected from the group consisting of C2-C 18 Alkyl dialdehydes, The group composed of.

3. The fluorescent nanoparticles according to claim 1, wherein the fluorescent nanoparticles are prepared by reacting polyethyleneimine with CHO(CH2) n The cationic cross-linked polyethyleneimine is prepared by reacting CHO, wherein n is an integer selected from 2-10. The fluorescent nanoparticles according to claim 1 , wherein the cationic cross-linked polyethyleneimine is prepared by reacting polyethyleneimine with glutaraldehyde. 5 . The fluorescent nanoparticles according to claim 1 , wherein the cationic cross-linked polyethyleneimine is prepared by reacting a cross-linking agent with polyethyleneimine, and the polyethyleneimine is selected from the group consisting of branched polyethyleneimine, linear polyethyleneimine, and a mixture thereof. The fluorescent nanoparticles according to claim 5 , wherein the weight average molecular weight of the polyethyleneimine is 1,000-1,000,000 kDa.

7. The fluorescent nanoparticles according to claim 1, wherein R 1 is hydrogen, methyl or ethyl; and R 2 Yes -CO2 - or -CO2(CH2) m CO2 - , wherein m is an integer selected from 1-2.

8. The fluorescent nanoparticles according to claim 1, wherein R 1 is hydrogen or methyl; and R 2 Yes -CO2 - or -CO2(CH2)2CO2 - .

9. The fluorescent nanoparticle of claim 1, wherein the anionic polymer comprises anionic poly(acrylic acid), anionic poly(methacrylic acid), anionic poly(2-carboxyethyl acrylate), or a copolymer or mixture thereof.

10. The fluorescent nanoparticles according to claim 1, wherein the C2-C 18 The cationic cross-linked polyethyleneimine is prepared by reacting an alkyl dialdehyde with polyethyleneimine, wherein the polyethyleneimine is selected from the group consisting of branched polyethyleneimine, linear polyethyleneimine and mixtures thereof, wherein the polyethyleneimine has a weight average molecular weight of 1,000-1,000,000 kDa; R 1 is hydrogen, methyl or ethyl; and R 2 Yes -CO2 - or -CO2(CH2) m CO2 - , wherein m is an integer selected from 1-2.

11. The fluorescent nanoparticles according to claim 1, wherein the cationic cross-linked polyethyleneimine is prepared by reacting glutaraldehyde with a branched polyethyleneimine, wherein the polyethyleneimine has a weight average molecular weight of 10,000-30,000 kDa; and the anionic polymer comprises anionic poly(acrylic acid), anionic poly(methacrylic acid), anionic poly(2-carboxyethyl acrylate), or a copolymer or mixture thereof. 12 . The fluorescent nanoparticles according to claim 1 , wherein the cationic cross-linked polyethyleneimine and the anionic polymer are present in the zwitterionic complex at a mass ratio of 1:1 to 1:4, respectively.

13. The fluorescent nanoparticles according to claim 1, wherein the cationic cross-linked polyethyleneimine is prepared by reacting glutaraldehyde with a branched polyethyleneimine, wherein the polyethyleneimine has a weight average molecular weight of 20,000-30,000 kDa; and the anionic polymer comprises anionic poly(acrylic acid), anionic poly(methacrylic acid), anionic poly(2-carboxyethyl acrylate), or a copolymer or mixture thereof. The fluorescent nanoparticles according to claim 13 , wherein the anionic polymer comprises anionic poly(methacrylic acid), and the cationic cross-linked polyethyleneimine and the anionic poly(methacrylic acid) are present in the zwitterionic complex at a mass ratio of 1:2 to 1:3, respectively. 15 . The fluorescent nanoparticles according to claim 14 , wherein the glutaraldehyde and the branched polyethyleneimine are reacted at a pH of about 3.

16. A method for preparing the fluorescent nanoparticles of claim 1, the method comprising combining a cross-linked polyethyleneimine and at least one anionic polymer precursor to form a reaction mixture; and polymerizing the at least one anionic polymer precursor with a polymerization agent to form the nanoparticles, wherein each of the at least one anionic polymer precursor independently has Formula 2: where R 1 is hydrogen or C1-C3 alkyl; and R 2 is -CO2H or -(CH2) m CO2H, wherein m is an integer selected from 1-4.

17. The method of claim 16, wherein the polymerization agent comprises ultraviolet radiation, a free radical initiator, heat, or a combination thereof.

18. The method of claim 17, wherein the free radical initiator is a peroxide.

19. The method of claim 16, further comprising combining polyethyleneimine and a cross-linking agent selected from the group consisting of: C2-C 18 Alkyl dialdehydes, Thereby, the cross-linked polyethyleneimine is formed.

20. The method according to claim 19, wherein the polyethyleneimine and the C2-C 18 The alkyl dialdehydes are combined at a pH of approximately 3.

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