Photochromic tungsten oxide composition and process for the preparation thereof

Abstract

The present invention provides a photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides coated with at least one alkanol containing at least 7 carbon atoms, and an inorganic complex of tungsten and said at least one alkanol; as well as a process for the preparation thereof. The invention further relates to a masterbatch comprising a polymer, e.g., polyethylene, incorporated with said photochromic tungsten oxide composition, and a polyethylene greenhouse cover comprising said masterbatch.

Description

ECOG-OOl PCTPHOTOCHROMIC TUNGSTEN OXIDE COMPOSITION AND PROCESS FOR THE PREPARATION THEREOFTECHNICAL FIELD

[0001] The present invention relates to a photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides coated with at least one alkanol containing at least 7 carbon atoms, and an inorganic complex of tungsten and said at least one alkanol; as well as a process for the preparation thereof.BACKGROUND ART

[0002] Greenhouse farming is a cornerstone of modem agriculture, providing controlled environments to enhance crop productivity and ensure food security. However, heat stress in greenhouses remains a major challenge, particularly in regions with high ambient temperatures. Excessive heat reduces crop yields, increases water demand, and compromises plant health. With rising global temperatures due to climate change, the need for effective solutions to mitigate greenhouse heat stress has become increasingly urgent.

[0003] Existing technologies and approaches in the industry and literature have attempted to address heat stress in greenhouses. These include:Shading nets: Widely used to block solar radiation and reduce temperatures, shading nets often obstruct both infrared (IR) and photosynthetically active radiation (PAR). This creates a trade-off, as the reduction in PAR can hinder plant photosynthesis and overall growth.Mechanical cooling systems: Active cooling methods, such as fans and evaporative cooling, are resource-intensive, requiring significant energy and water inputs. These systems are often costly, require regular maintenance, and are unsuitable for many greenhouse operators in resource-limited areas.Fixed-property greenhouse films: Commercial greenhouse films, including those developed by companies like Kafrit (Israel) and SecondSky (Abu Dhabi), utilize fixed reflective or absorptive properties to manage heat. However, these films are unable to adapt to varying environmental conditions dynamically. As a result, they may overcool greenhouses during mild conditions or fail to mitigate heat stress sufficiently during peak temperatures.ECOG-OOl PCTSUMMARY OF INVENTION

[0004] In one aspect, disclosed herein is a process for the preparation of a photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides (i.e., WOs-x) coated with at least one alkanol containing at least 7 carbon atoms; and an inorganic complex of tungsten and said at least one alkanol, said process comprising:(i) introducing tungsten hexacarbonyl (W(CO)e), optionally in the form of a powder, into a liquid medium comprising said at least one alkanol, to thereby obtain a reaction mixture;(ii) heating the reaction mixture at a temperature higher than the melting temperature of said at least one alkanol but not higher than 100°C, while stirring, under ambient pressure, for a period of from a few seconds up to about 10 minutes, to thereby facilitate mixing of said tungsten hexacarbonyl and said at least one alkanol;(iii) heating the reaction mixture thus obtained at a temperature from about 150°C to about 200°C, for a period not exceeding 60 minutes, while said reaction mixture is covered, to thereby facilitate partial oxidation of said tungsten hexacarbonyl and consequently obtain said nanostructures; and(iv) fast cooling the reaction mixture thus obtained to a temperature lower than 100°C, e.g., room temperature, wherein the color of said reaction mixture during the heating step (iii) first becomes yellow, and then gradually changes from yellow to green and from green to blue as said heating proceeds, and wherein the cooling step (iv) is initiated not before the color of said reaction mixture is purely green; and in case the color of said reaction mixture is purely blue, as long as upon exposure to ultraviolet (UV) irradiation, said mixture reaction exhibits a photochromic shift from blue to green.

[0005] The photochromic tungsten oxide composition prepared by the process disclosed herein is characterized by a peak at 420 nm in the ultraviolet-visible (UV-Vis) spectrum, which is exhibited upon exposure of said photochromic tungsten oxide composition to UV irradiation. As shown herein, said peak seems to be attributed to the inorganic complex of tungsten and said at least one alkanol, formed in the reaction mixture during the heating step (iii) as an intermediate compound prior to the formation of the sub-stoichiometric tungstenECOG-OOl PCT oxides, and the intensity of said peak is in positive correlation with the amount of said inorganic complex in said composition. As further shown, the amount of said inorganic complex in the reaction mixture is at its maximum at a stage wherein the color of the reaction mixture has completely changed from yellow to green, and gradually decreases as the amount of the tungsten oxides in the reaction mixture increases and the color of the reaction mixture gradually changes from green to blue. Importantly, the fact that the heating step (iii) is terminated at the latest when the color of said reaction mixture is purely blue but as long as upon exposure to UV irradiation said mixture reaction exhibits a photochromic shift from blue to green, actually guarantees that any composition obtained by the process disclosed, provided that the cooling step is initiated not before the color of said reaction mixture is purely green, will comprise said inorganic complex and will thus be characterized, upon exposure to UV irradiation, by said peak. In this respect, it should be noted that the actual time frame during which the reaction mixture is heated in step (iii), which may not exceed 60 minutes, depends on the temperature at which said step is carried out and is generally shorter as the temperature increases. For example, while the time frame required to obtain a composition which, upon exposure to UV irradiation, is characterized by a strong peak at 420 nm may reach up to 50-60 minutes at 150°C, it may be not more than 20-30 minutes at 200°C.

[0006] The photochromic properties of the composition prepared by the process disclosed herein depends on the stage at which the cooling step (iv) is initiated, i.e., on the amount of the sub-stoichiometric tungsten oxides, and the ratio between these oxides and the inorganic complex, in said composition. Specifically, in certain embodiments, the cooling step (iv) is initiated at a stage wherein the color of the reaction mixture is purely green, and upon exposure to UV irradiation said composition consequently further exhibits a spontaneous reversible photochromic shift from light green to strong yellow. In other embodiments, the cooling step (iv) is initiated at a stage wherein the color of said reaction mixture is either blue or in a phase of changing from green to blue, and upon exposure to UV irradiation said composition consequently further exhibits a spontaneous reversible photochromic shift from blue to green, and an enhanced IR absorption, i.e., increased IR responsiveness.

[0007] In another aspect, disclosed herein is a photochromic tungsten oxide composition comprising (a) nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides (i.e., WCh-x) coated with at least one alkanol containing at least 7 carbon atoms; and (b) an inorganic complex of tungsten and said at least one alkanol. Such aECOG-OOl PCT photochromic tungsten oxide composition may be obtained, e.g., by the process defined above.

[0008] In yet another aspect, disclosed herein is a masterbatch comprising a polymer incorporated with a photochromic tungsten oxide composition as defined above. In certain embodiments, the polymer incorporated with said composition is polyethylene.

[0009] In still another aspect thus disclosed herein is a polyethylene greenhouse cover comprising (e.g., made of) a masterbatch comprising polyethylene incorporated with a photochromic tungsten oxide composition as defined above.

[0010] In a further aspect, disclosed herein is a non-photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub- stoichiometric tungsten oxides (i.e., WOs-x) coated with at least one alkanol containing at least 7 carbon atoms, obtained by the process of the present invention, wherein the cooled reaction mixture obtained following step (iv) of said process is in liquid form, and has been centrifuged, optionally while washing with an organic solvent to dissolve said at least one alkanol and prevent its solidification, to thereby remove said inorganic complex from the composition, optionally followed by drying. Said non-photochromic tungsten oxide composition, which is inorganic complex free, exhibits IR absorption properties that are not enhanced upon exposure to UV irradiation, but neither a peak at 420 nm in the UV-Vis spectrum nor a spontaneous reversible photochromic shift from blue to green.

[0011] In yet a further aspect, disclosed herein is an article, e.g., a lens such as a sunglass’ lens, comprising (e.g., made of) a plastic incorporated with either a photochromic tungsten oxide composition or a non-photochromic tungsten oxide composition, each as defined above.BRIEF DESCRIPTION OF DRAWINGS

[0012] Fig. 1 shows spectral changes demonstrating IR enhancement and the emergence of a 420 nm peak in tungsten oxide-hexadecanol after 0 minutes (solid line); 5 minutes (dotted line); and 10 minutes (dashed line) of UV exposure.

[0013] Fig. 2 shows the optical properties of the tungsten oxide solution in hexane in the dark (triangle line ( A Dark 1)), after exposure to UV light (diamond line (• UV 1)), and then after relaxing in the dark again (square line (♦ Dark 2)).ECOG-OOl PCT

[0014] Fig. 3 shows reversibility of the photoresponse of tungsten oxide to sunlight. Optical images of the solution: (a) before exposure to sunlight, (b) after exposure to sunlight, (c) after several minutes indoors, and (d) after re-exposure to sunlight.

[0015] Figs. 4A-4D show optical properties of tungsten oxide in hexadecanol at 200°C for 10, 20, 30, and 60 minutes (4 A, 4B, 4C and 4D, respectively). Each figure shows spectra before UV exposure (solid line), as well as after 5 and 10 minutes of UV exposure (dotted line and dashed line, respectively). The 20-minute reaction (4B) shows the strongest 420 nm peak, which diminishes at longer reaction times.

[0016] Figs. 5A-5C show tungsten oxide in hexadecanol before and after UV exposure (5A); washed tungsten oxide before and after UV exposure (5B); and removed hexadecanol solution before and after UV exposure (5C). Solid line: before UV irradiation, dashed line: after UV exposure.

[0017] Figs. 6A-6D show the effect of temperature on the reaction between tungsten hexacarbonyl and hexadecanol: (6A) 170°C, (6B) 180°C, (6C) 190°C, and (6D) 200°C. Solid line: before UV irradiation (0 min), dotted line: after 5 minutes of UV exposure, and dashed line: after 10 minutes of UV exposure

[0018] Figs. 7A-7C show optical properties of tungsten oxide in solvents with varying alkyl chain lengths (dodecanol (7 A), tetradecanol (7B), and hexadecanol (7C). Each figure shows UV-Vis-NIR absorption spectra recorded before UV exposure (solid line) and after 5 and 10 minutes of UV exposure (dotted line and dashed line, respectively). An increase in the intensity of the 420 nm absorption peak and IR enhancement is observed with increasing chain length.

[0019] Figs. 8A-8B show XRD structural characterization of the product prepared in Study 1. (8A) Diffraction pattern showing the characteristic peaks of hexadecanol and unreacted tungsten hexacarbonyl (W(CO)e), confirming their partial presence in the synthesized product. (8B) XRD pattern highlighting the formation of sub-stoichiometric tungsten oxides - W5O14, W20O58, W18O49, W25O73 - indicating a mixture of reduced tungsten species formed during the reaction.

[0020] Figs. 9A-9C show IR absorption of tungsten oxide with copper salt added at different reaction times: (9 A) 0 min, (9B) 10 min, and (9C) 15 min (total reaction time was 20 min in all cases). Each figure shows spectra before UV exposure (solid line) and after 5 and 10 minutes of UV exposure (dotted line and dashed line, respectively). Maximum IR enhancement (~4x) appears at 15 min.ECOG-OOl PCT

[0021] Figs. 10A-10F show optical properties of Cu-W oxide nanostructures prepared with varying W:Cu ratios: 100:0 (W:C, 10A), 90: 10 (W:C, 10B), 75:25 (W:C, 10C), 50:50 (W:C, 10D), 25:75 (W:C, 10E), and 0:100 (W:C, 10F). Each figure shows spectra recorded before UV exposure (solid line) and after 5 and 10 minutes of UV exposure (dotted line and dashed line, respectively). The formulation with 25% Cu (10C) shows optimal absorption in both the UV and IR regions.

[0022] Fig. 11 shows sunlight irradiance at noon on 20.08.24 in Baqa al-Gharbiyye, Israel (black line), passing through a 150-micron PE cover film (dotted line), and passing through a 150-micron PE film containing sub-stoichiometric tungsten oxides structures (dashed line).

[0023] Fig. 12 shows optical image of the greenhouse covered with PE film with (right) and without (left) sub-stoichiometric tungsten oxides structures.

[0024] Figs. 13A-13C show tracking the temperature inside the greenhouse at the upper (13A), the middle (13B), and the bottom (13C). The dashed line represents the PE cover film without the additive, while the solid line corresponds to the film containing the non- stoichiometric tungsten oxide additive.

[0025] Fig. 14 shows temperature difference between cover films with and without sub- stoichiometric tungsten oxide additive.DETAILED DESCRIPTION

[0026] The present invention introduces a novel greenhouse heat stress management approach by developing a unique tungsten oxide-based composition. Unlike conventional tungsten oxide materials, this composition demonstrates photochromic behavior and enhanced IR absorption upon exposure to UV radiation. This represents a significant advancement over existing technologies, as tungsten oxide materials with these combined properties have not been previously reported.

[0027] In one aspect, disclosed herein is a process for the preparation of a photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides coated with at least one alkanol containing at least 7 carbon atoms; and an inorganic complex of tungsten and said at least one alkanol, said process comprising:(i) introducing tungsten hexacarbonyl, optionally in the form of a powder, into a liquid medium comprising said at least one alkanol, to thereby obtain a reaction mixture;ECOG-OOl PCT(ii) heating the reaction mixture at a temperature higher than the melting temperature of said at least one alkanol but not higher than 100°C, while stirring, under ambient pressure, for a period of from a few seconds up to about 10 minutes, to thereby facilitate mixing of said tungsten hexacarbonyl and said at least one alkanol;(iii) heating the reaction mixture thus obtained at a temperature from about 150°C to about 200°C, for a period not exceeding 60 minutes, while said reaction mixture is covered, to thereby facilitate partial oxidation of said tungsten hexacarbonyl and consequently obtain said nanostructures; and(iv) fast cooling the reaction mixture thus obtained, e.g., using a cooling bath or ice bath, to a temperature lower than 100°C, e.g., room temperature, wherein the color of said reaction mixture during the heating step (iii) first becomes yellow, and then gradually changes from yellow to green and from green to blue as said heating proceeds, and wherein the cooling step (iv) is initiated not before the color of said reaction mixture is purely green; and when the color of said reaction mixture is purely blue, as long as upon exposure to UV irradiation, said mixture reaction exhibits a photochromic shift from blue to green.

[0028] According to the process of the present invention, the reaction mixture is obtained in step (i) by introducing tungsten hexacarbonyl, optionally in the form of a powder, into a liquid medium comprising said at least one alkanol, i.e., into a liquid medium containing said at least one alkanol in an entirely melted form.

[0029] In addition, whereas the heating step (ii), carried out at a temperature of up to 100°C, is aimed at facilitating mixing of said tungsten hexacarbonyl and said at least one alkanol, the heating step (iii), carried out at a temperature from about 150°C to about 200°C while said reaction mixture is covered, is aimed at facilitating partial oxidation of said tungsten hexacarbonyl in said reaction mixture and consequently obtaining the desired nanostructures. The covering is essential for managing the exposure of said reaction mixture to oxygen, and it may be practically done using, e.g., a cap or a foil.

[0030] As stated above, the amount of the inorganic complex, formed in the reaction mixture as an intermediate compound prior to the formation of the sub-stoichiometric tungsten oxides, is at its maximum at a stage wherein the color of the reaction mixture has completely changed from yellow to green, and gradually decreases as the amount of theECOG-OOl PCT tungsten oxides in the reaction mixture increases and the color of the reaction mixture gradually changes from green to blue.

[0031] In certain embodiments, disclosed herein is a process as defined above, wherein the cooling step (iv) is initiated at a stage wherein the color of said reaction mixture is purely green; and upon exposure to UV irradiation, said photochromic tungsten oxide composition exhibits a peak at 420 nm in the UV-Vis spectrum and a spontaneous reversible photochromic shift from light green to strong yellow.

[0032] In other embodiments, disclosed herein is a process as defined above, wherein the cooling step (iv) is initiated at a stage wherein the color of said reaction mixture is either blue or in a phase of changing from green to blue; and upon exposure to UV irradiation, said photochromic tungsten oxide composition exhibits a peak at 420 nm in the UV-Vis spectrum, a spontaneous reversible photochromic shift from blue to green, and an enhanced IR absorption, i.e., increased IR responsiveness.

[0033] The phrase “spontaneous reversible photochromic shift” as used herein with respect to the photochromic tungsten oxide composition means that the photochromic shift characterizing said composition upon exposure to UV irradiation occurs spontaneously, i.e., without an external trigger such as an electric field (Deb et cd.. 2008; Moshofsky and Mokari, 2014) or pH alteration (Sun et al., 2000), and is reversible.

[0034] The phrase “sub-stoichiometric tungsten oxide” as used herein refers to a tungsten oxide comprising less than the stoichiometric amount of oxide, i.e., a tungsten oxide comprising, in average, less than three oxygen atoms linked to each tungsten atom (WCh-x, wherein X is >0 and <1). In certain embodiments, the sub-stoichiometric tungsten oxides referred to are each selected from WO2.625 (W32O84; WsOs), WO2.725 (W18O49), WO2.785 (W17O47), WO2.8 (W5O14), WO2.9 (W20O58), and WO2.92 (W25O73). In particular such embodiments, the sub-stoichiometric tungsten oxides referred to comprise at least one of W5O14, W20O58, W18O49, and W25O73. In more particular such embodiments, said sub- stoichiometric tungsten oxides comprise W5O14 and W20O58; W5O14 and W18O49; W5O14 and W25O73; W20O58 and W18O49; W20O58 and W25O73; W5O14, W20O58 and W18O49; W5O14, W20O58 and W25O73; W20O58, W18O49, and W25O73; or each one of W5O14, W20O58, W18O49, and W25O73.

[0035] The term “inorganic complex” or “coordination complex” used herein interchangeably with respect to the intermediate compound formed in the reaction mixture during the heating step (iii) and prior to the formation of the sub-stoichiometric tungstenECOG-OOl PCT oxides, refers to a chemical complex formed by the association of tungsten atom or ion (acting as a coordination center) with a surrounding array of said alkanol molecules (ligands), wherein the linkage between the tungsten and each one of the alkanol molecules is through a lone pair of the oxygen atom of said alkanol molecule.

[0036] The term “alkanol” as used herein refers to a linear or branched alkane containing at least 7, preferably 10-22, carbon atoms, in which one of the hydrogen atoms is replaced by -OH group. Particular such molecules are linear alkanols, e.g., linear alkanols wherein the -OH group is on one of the terminal carbon atoms such as 1 -decanol, 1 -dodecanol (lauryl alcohol), 1 -tetradecanol (myristyl alcohol), 1 -hexadecanol (cetyl alcohol), 1 -octadecanol (stearyl alcohol), 1-eicosanol (arachidyl alcohol), and 1 -docosanol (behenyl alcohol). In specific embodiments, said alkanol is 1 -hexadecanol.

[0037] In certain embodiments, disclosed herein is a process as defined in any one of the embodiments above, wherein the liquid medium into which the tungsten hexacarbonyl is introduced in step (i) has been prepared by heating said at least one alkanol to a temperature above its melting point. According to the present invention, the tungsten hexacarbonyl may be introduced into said liquid medium at different stages of said heating, e.g., at an early stage of said heating to facilitate gradual oxidation as the temperature further increases; or once the liquid medium reaches a higher temperature, allowing for faster oxidation and different phase development. In a particular such embodiment, said at least one alkanol is 1 - hexadecanol, and said liquid medium has been prepared by heating 1 -hexadecanol to a temperature above 50°C.

[0038] The weight ratio between the tungsten hexacarbonyl and the alkanol(s) in the reaction mixture obtained in step (i) affects the reaction environment and, consequently, tungsten oxides’ oxidation dynamics and final properties. At lower W(CO)e-to-alkanol ratios (excess alkanol), the reaction medium is more dilute, leading to slower oxidation and extended nucleation phases, which can result in smaller or less aggregated particles with relatively fewer defects. Higher ratios (less alkanol) create a more concentrated environment, accelerating reaction kinetics and promoting rapid nucleation and oxidation, often forming more defective structures with oxygen vacancies. These defects can enhance properties such as IR absorption but may compromise stability. Controlling this ratio is critical to tailoring the tungsten oxide nanostructures’ morphology, phase, and functionality for specific applications, such as improving photochromic or IR-responsive behaviors. In certain embodiments, disclosed herein is a process as defined in any one of the embodiments above,ECOG-OOl PCT wherein the amount of tungsten hexacarbonyl introduced into the liquid medium constitutes from about 1.25% to about 20% by weight of reaction mixture obtained, i.e., the ratio between said tungsten hexacarbonyl and said at least one alkanol in said reaction mixture is from about 1 :80 to about 1 :5, by weight, respectively.

[0039] In certain embodiments, disclosed herein is a process as defined in any one of the embodiments above, wherein (1) said at least one alkanol is 1 -hexadecanol; and said reaction mixture is heated in step (ii) at a temperature of about 80°C, preferably for a period of about 5 minutes; and / or (2) said heating in step (iii) is carried out for about 20 minutes.

[0040] Thus, in one particular such aspect, disclosed herein is process for the preparation of a photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides coated with 1 -hexadecanol; and an inorganic complex of tungsten and 1 -hexadecanol, said process comprising:(i) introducing tungsten hexacarbonyl, optionally in the form of a powder, into a liquid medium comprising 1 -hexadecanol, to thereby obtain a reaction mixture;(ii) heating the reaction mixture at a temperature of about 80°C, while stirring, under ambient pressure, for a period of up to about 10 minutes, preferably about 5 minutes, thereby facilitating mixing of said tungsten hexacarbonyl and said 1 -hexadecanol;(iii) heating the reaction mixture thus obtained at a temperature from about 150°C to about 200°C, for a period of about 20 minutes, while said reaction mixture is covered, thereby facilitating partial oxidation of said tungsten hexacarbonyl and consequently obtaining said nanostructures; and(iv) fast cooling the reaction mixture thus obtained to a temperature lower than 100°C, e.g., room temperature, wherein the color of said reaction mixture during the heating step (iii) first becomes yellow, and then gradually changes from yellow to green and from green to blue as said heating proceeds, and wherein the cooling step (iv) is initiated not before the color of said reaction mixture is purely green; and when the color of said reaction mixture is purely blue, as long as upon exposure to UV irradiation, said mixture reaction exhibits a photochromic shift from blue to green.

[0041] In other embodiments, disclosed herein is a process as defined in any one of the embodiments above, wherein the liquid medium into which said tungsten hexacarbonyl isECOG-OOl PCT introduced in step (i) further comprises a mineral oil or a component thereof, and said at least one alkanol constitutes at least 5% by weight of said liquid medium. The addition of mineral oil or a component thereof, which does not chemically react with the tungsten, serves as a diluent, influencing the viscosity of the reaction mixture and the reaction environment, which in turn modulate the kinetics of tungsten oxide formation. The inclusion of a mineral oil or a component thereof can impact the nucleation and growth of tungsten oxide nanostructures, as well as the overall reaction dynamics, by altering the distribution and mobility of reactive species. As demonstrated in related studies, the use of mineral oil in alkanol-based solvent systems can promote or inhibit structural formation depending on its ratio with the active alkanol (Moshofsky and Mokari, 2013). Maintaining at least 5% alkanol in the reaction medium is critical, as the presence of alkanol is essential for initiating and sustaining the synthesis of tungsten oxide nanostructures. This flexibility in the solvent composition allows for fine-tuning of the reaction parameters to achieve optimal nanostructure properties without compromising the integrity of the synthesis process. The ratio between the at least one alkanol and the mineral oil or component thereof in the liquid medium should thus be optimized to balance the reaction kinetics and ensure the controlled formation of tungsten oxide nanostructures with the desired properties. In particular such embodiments, the weight ratio between said at least one alkanol and said mineral oil or component thereof in said liquid medium is from about 3: 1 to about 1 :3, e.g., about 3: 1, about 2: 1, about 1 : 1, about 1 :2, or about 1 :3, respectively. In particular such embodiments, said mineral oil or component thereof is (C?-C2o)alkane, i.e., a linear or branched hydrocarbon containing 7-20 carbon atoms. In specific such embodiments, said alkane corresponds to said at least one alkanol, i.e., has a structure from which said alkanol may theoretically be obtained by substituting one of the hydrogen atoms with -OH, e.g., said alkanol is 1 -hexadecanol; and said alkane is hexadecane.

[0042] In certain embodiments, disclosed herein is a process as defined in any one of the embodiments above, wherein the cooled reaction mixture obtained in step (iv) is in the form of a solid or semi-solid, and said process further comprises the step of (v) grinding the solidified reaction mixture to fine powder, e.g., to a powder comprising particles having a size ranging from about 10 to about 100 microns. The grinding step may be conducted using any suitable technology and following any procedure known in the art.

[0043] In another aspect, disclosed herein is a photochromic tungsten oxide composition comprising (a) nanostructures made of a core comprising a plurality of sub-stoichiometricECOG-OOl PCT tungsten oxides coated with at least one alkanol containing at least 7 carbon atoms; and (b) an inorganic complex of tungsten and said at least one alkanol. Such a photochromic tungsten oxide composition may be obtained, e.g., by the process disclosed herein, according to any one of the embodiments above.

[0044] As discussed above, upon exposure to UV irradiation, the photochromic tungsten oxide composition disclosed exhibits a peak at 420 nm in the UV-Vis spectrum, and depending on the specific procedure by which it has been prepared, said composition further exhibits either a spontaneous reversible photochromic shift from light green to strong yellow; or a spontaneous reversible photochromic shift from blue to green, and an enhanced IR absorption. In certain embodiments, thus disclosed herein is a photochromic tungsten oxide composition as defined above, wherein upon exposure to UV irradiation, said composition exhibits a peak at 420 nm in the UV-Vis spectrum; a spontaneous reversible photochromic shift from blue to green; and optionally an increased IR responsiveness.

[0045] In yet another aspect, disclosed herein is a masterbatch comprising a polymer incorporated with a photochromic tungsten oxide composition as defined above. Examples of polymers to be used in such masterbatches include, without being limited to, polyethylene (PE), polypropylene, polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), and ethylene vinyl acetate (EVA). In certain embodiments, the polymer incorporated with said composition is polyethylene. In particular embodiments, the sub-stoichiometric tungsten oxides loading in said masterbatch is from about 0.001% to about 20% by weight (in case the composition incorporated within the polymer has been obtained by the process disclosed herein, the tungsten oxides loading may be calculated, e.g., on an assumed 100% yield of the reaction relative to the tungsten hexacarbonyl precursor. In particular such masterbatches, the nanostructures are evenly dispersed within said polymer.

[0046] As shown herein, a polyethylene-based masterbatch as disclosed herein and greenhouse cover films made of said masterbatch are highly effective for dynamic temperature regulation in greenhouses. The films reduce heat stress in summer while maintaining light transmittance critical for plant growth. This application enhances agricultural productivity and sustainability.

[0047] In still another aspect thus disclosed herein is a polyethylene greenhouse cover comprising (e.g., made of) a masterbatch as disclosed herein, according to any one of the embodiments above, i.e., a masterbatch comprising polyethylene incorporated with a photochromic tungsten oxide composition as disclosed herein.ECOG-OOl PCT

[0048] The photochromic tungsten oxide composition disclosed herein may be useful in additional various industries, including:(i) Paints and coatings. Tungsten oxide’s photochromic and IR absorption properties can be utilized in energy-efficient paints and coatings. These coatings could regulate heat transfer in buildings or vehicles, reducing cooling and heating demands. Additionally, the photochromic effect offers potential for smart exterior or interior coatings that adapt to sunlight exposure.(ii) Sunglass filters and optical devices. The photochromic behavior of tungsten oxide makes it an excellent candidate for sunglass filters that dynamically adjust to light intensity. This technology can be extended to lenses for optical devices, including cameras, smart glasses, and visors, enhancing user comfort and performance.(iii) Smart packaging materials. Incorporating tungsten oxide into flexible films could provide smart packaging solutions that protect temperature-sensitive goods, such as pharmaceuticals or food, by dynamically regulating temperature exposure during storage and transport.(iv) Automotive applications. The material could be used in car windows, windshields, or coatings to reduce interior temperatures, improving fuel efficiency by decreasing reliance on air conditioning.

[0049] In a further aspect, disclosed herein is a non-photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub- stoichiometric tungsten oxides coated with at least one alkanol containing at least 7 carbon atoms, obtained by the process of the present invention, wherein the cooled reaction mixture obtained following step (iv) is in liquid form, and has been centrifuged, optionally while washing with an organic solvent to dissolve said at least one alkanol and prevent its solidification, to thereby remove said inorganic complex from the composition, optionally followed by drying.

[0050] In certain embodiments, the organic solvent used for washing the cooled reaction mixture is a polar organic solvent, a non-polar organic solvent, or a mixture thereof. Examples of polar organic solvents include, without limiting, acetic acid, acetone, acetonitrile, dimethylformamide (DMF), dimelthylsulfoxide (DMSO), methanol, ethanol, propanol, isopropanol, butanol, / -butyl alcohol, chlorobenzene, 1,2-di chloroethane, ethylene glycol, diethylene glycol, ethyl acetate, and methylene chloride. Examples of non-polarECOG-OOl PCT organic solvents include, without being limited to, hexane, cyclohexane, chloroform, diethyl ether, toluene, xylene, tetrachloroethylene, n-heptane, isooctane, and benzene.

[0051] As stated above, in view of the process for obtaining the non-photochromic tungsten oxide composition, said composition is inorganic complex free, and therefore exhibits IR absorption properties that are not enhanced upon exposure to UV irradiation, but neither a peak at 420 nm in the UV-Vis spectrum nor a spontaneous reversible photochromic shift from blue to green.

[0052] In yet a further aspect, disclosed herein is an article comprising (e.g., made of) a plastic incorporated with either a photochromic tungsten oxide composition or a non- photochromic tungsten oxide composition, each as disclosed herein according to any one of the embodiments above. In certain embodiments, the article disclosed is a lens, e.g., a sunglass’ lens.

[0053] Unless otherwise indicated, all numbers referring, e.g., temperatures, time periods, percentages, and ratios, used in the present specification 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 this description and claims are approximations that may vary by up to plus or minus 10% depending upon the desired properties sought to be obtained by the invention.

[0054] The invention will now be illustrated by the following non-limiting Examples.EXAMPLESMaterials and Methods

[0055] Materials. 1 -decanol (DO; >98%), 1 -dodecanol (lauryl alcohol, >98%), 1- tetradecanol (TDO; myristyl alcohol, >98%), 1 -hexadecanol (HDO; cetyl alcohol, >98%), 1 -octadecanol (stearyl alcohol, >98%), 1-eicosanol (arachidyl alcohol, >98%), and 1- docosanol (behenyl alcohol, >98%), and Paraffin oil (light). Tungsten hexacarbonyl (W(CO)e, >97%), and copper chloride (CuCh 2H2O, >95%).

[0056] General procedure. A 20 mL vial was charged with 4 g of 100% HDO and placed in a preheated oil bath at 100°C to ensure complete melting of the solvent. Once the solvent was fully melted, 200 mg of tungsten hexacarbonyl (W(CO)e) was added to the vial. The vial was then transferred to a second preheated oil bath set to a target temperature (150- 200°C), and the reaction was allowed to proceed for a defined period (10-30 minutes). AfterECOG-OOl PCT the reaction, the vial was removed from the oil bath and allowed to cool before analyzing the IR properties using a spectrophotometer.

[0057] Experimental variations. Temperature effects: Reactions were conducted at varying oil bath temperatures (170°C, 180°C, 190°C, 200°C) to determine the optimal conditions for IR behavior and nanostructure formation. Solvent-to-oil ratios: The following ratios of HDO to paraffin oil (hexadecane) were tested: 25% HDO and 75% oil, 50% HDO and 50% oil, 75% HDO and 25% oil, and 100% HDO. Each ratio was investigated over different reaction times (10, 15, 20 minutes) to assess the influence on reaction kinetics. Solvent types: Three solvents - HDO, TDO, and DO - were compared at a 50% solvent-to- oil ratio to study their impact on UV and IR behavior. Copper additive: Copper chloride (CuCh 2H2O) was added in select experiments to evaluate its effect on the reaction mechanism and IR behavior.

[0058] Analytical methods. The reaction products were analyzed using a spectrophotometer to evaluate their IR spectra. Measurements were taken before and after UV irradiation (up to 15 minutes) to observe changes in IR behavior. Color changes in the reaction mixture were monitored as an indicator of the reaction progress, and the UV absorption properties were recorded to assess the effect of solvent type.Study 1. Formation of tungsten oxide (blue phase)

[0059] The tungsten oxide in the blue phase was formed directly within the hexadecanol matrix, which played a dual role as solvent and ligand during the reaction. Notably, the synthesis process did not require any purification or separation steps for the tungsten oxide, as the optical properties were analyzed directly from the material embedded in the hexadecanol. This approach highlights the efficiency of the process and its suitability for practical applications.

[0060] The blue-phase tungsten oxide exhibited distinct IR properties, as shown by the solid line in Fig. 1. However, an intriguing phenomenon was observed when this phase was exposed to UV radiation. A new peak emerged at 420 nm in the UV-visible spectrum, and the IR properties were significantly enhanced, as evidenced by the dashed and dotted lines in Fig- 1 This suggests a strong interaction between the tungsten oxide and the hexadecanol matrix under UV exposure.ECOG-OOl PCT

[0061] After discussing the formation of tungsten oxide, the optical properties of the product under UV exposure and its subsequent recovery were analyzed. These observations highlight the material’s reversible photochromic behavior, a key feature of the tungsten oxide phase.

[0062] Fig. 2 presents the optical properties of tungsten oxide before, during, and after UV exposure. The spectra demonstrate that UV exposure induces a new peak at 420 nm and enhances the material’s IR properties. Notably, after stopping the UV exposure, the optical properties gradually return to their original state, confirming the reversible nature of the photochromic behavior.

[0063] Moreover, Fig. 3 provides optical images of the tungsten oxide solution. The first frame shows the solution before UV exposure, appearing in its original state. The second frame depicts the solution during UV exposure, where a visible color change occurs due to the formation of the photochromic phase. The third frame shows the solution after UV exposure has stopped, demonstrating the gradual return to the initial appearance as the photochromic effect reverses.

[0064] To better understand the key factors influencing the reaction between tungsten hexacarbonyl (W(CO)e) and 100% HDO, a series of controlled experiments were performed to assess the impact of several critical parameters. Specifically, the effects of temperature, reaction time, and copper chloride (CuCh 2H2O) addition were evaluated. Each factor was systematically varied to examine how they influence the reaction kinetics and the resulting products, focusing on IR behavior. By systematically investigating these experimental parameters, we aimed to identify the most significant factors affecting the reaction, optimize reaction conditions, understand how these variables contribute to the overall reaction mechanism, and choose the right conditions for optimal product. Unless stated otherwise, all experiments were conducted using the general synthesis procedure to ensure consistency and comparability when studying the various parameters.

[0065] Reaction time effect. The effect of reaction time on the formation of tungsten oxide in hexadecanol at 200°C was analyzed, with the results presented in Fig. 4. Optical properties were used as a critical tool to understand the progression of the reaction, the interaction between tungsten oxide and hexadecanol, and the stability of the resulting structures under UV exposure.ECOG-OOl PCT

[0066] IR-active structures begin forming at 10 minutes (Fig. 4a), and the 420 nm peak appears after UV exposure. This marks the initial stage of tungsten oxide formation and its integration with the hexadecanol matrix. By 20 minutes (Fig. 4b), the 420 nm peak reaches maximum intensity, accompanied by the most vital IR enhancement. This indicates the optimal development of the tungsten-hexadecanol inorganic complex, where the balance between the tungsten oxide phase and its interaction with hexadecanol is most favorable.

[0067] At 30 minutes (Fig. 4c), the intensity of the 420 nm peak decreases, suggesting a reduction in the stability of the tungsten-hexadecanol inorganic complex or changes in its structure. By 60 minutes (Fig. 4d), the 420 nm peak is no longer present, and the IR enhancement significantly diminishes. This behavior likely results from the overreaction of tungsten oxide or further structural transformations that disrupt the complex’s ability to enhance IR and UV-visible properties.

[0068] These findings demonstrate how optical properties are a diagnostic tool for understanding the formation, interaction, and stability of the tungsten oxide phase and its associated complex. The results identify 20 minutes as the optimal reaction time to achieve the best UV-visible and IR properties balance. This offers insights for controlling synthesis conditions to target specific material characteristics.

[0069] Washing effect. To further understand the formation of the 420 nm peak and the enhancement of IR properties, the tungsten oxide was purified and separated from the excess hexadecanol. Interestingly, when the tungsten oxide was analyzed in isolation, the 420 nm peak was absent, and the IR properties were not enhanced, even upon UV exposure, as shown in Fig. 5 (middle). These findings indicate that the interaction with hexadecanol is crucial for both the generation of the 420 nm peak and the observed IR enhancement.

[0070] When the removed fraction of hexadecanol was reintroduced and exposed to UV radiation, the 420 nm peak reappeared, but the IR enhancement did not, as shown in Fig. 5 (bottom). This suggests that the 420 nm peak is associated with the complex between tungsten and hexadecanol, while the IR enhancement is an intrinsic property of the tungsten oxide itself. This differentiation highlights the distinct roles of the hexadecanol matrix in forming the tungsten-hexadecanol inorganic complex responsible for the 420 nm peak and the tungsten oxide in contributing to the IR properties.

[0071] Further investigations are required to elucidate the exact nature and role of the tungsten-hexadecanol interaction in forming the 420 nm peak. These insights could lead toECOG-OOl PCT new strategies for designing materials with tunable optical and IR properties for advanced applications.

[0072] Temperature effect. The objective was to investigate how varying the temperature influences the reaction between tungsten hexacarbonyl (W(CO)e) and 100% HDO.

[0073] Procedure: Four experiments were conducted using the standard procedure, with each reaction set at a different temperature. The reactions were initiated at 100°C to allow the solvent to melt entirely before being transferred to a preheated oil bath set to 170°C, 180°C, 190°C, or 200°C. A consistent reaction time of 20 minutes was maintained for all experiments to ensure the optimal formation of tungsten oxide and to observe the effects of temperature on the reaction kinetics and the optical properties of the resulting product.

[0074] As expected, increasing the temperature enhanced the reaction rate, resulting in faster and more efficient product formation. The IR spectra from reactions conducted at 190°C and 200°C (Figs. 6c and 6d, respectively) showed significantly enhanced IR behavior compared to those at lower temperatures. In contrast, reactions at 170°C (Fig. 6a) exhibited weaker absorption intensities, indicating less efficient product formation at lower temperatures. These results suggest that higher temperatures facilitate the breakdown of W(CO)e and promote additional reaction pathways, forming the desired tungsten nanowires.

[0075] Effect of different solvents. The objective was to investigate the effect of different solvent chain lengths on reaction efficiency and the resulting product characteristics.

[0076] Procedure; Three solvents, HDO, TDO, and DO, were tested. Each solvent was reacted with 200 mg of tungsten hexacarbonyl (W(CO)e). The reaction was initiated at 100°C to melt the solvent and ensure proper mixing, followed by an increase to 200°C in a preheated oil bath. The reaction time was maintained at 20 minutes.

[0077] Results. The chain length of the solvent molecules plays a crucial role in chemical reactions involving organometallic compounds. In this case, the alkyl chain length of the alcohol solvents influences the solubility of tungsten hexacarbonyl (W(CO)e), the dispersion of the reactants, and potentially the interaction between tungsten species and the solvent. Longer alkyl chains may promote better stabilization of the tungsten oxide species and influence optical properties, such as UV absorption and IR behavior. Examining these effects provides insight into the role of the solvent structure in reaction dynamics and the formation of photochromic tungsten oxide phases.ECOG-OOl PCT

[0078] As shown in Figs. 7A-7C, the type of solvent used did not significantly affect the overall reaction outcome, as all reactions exhibited similar color changes by the end of the 10-minute reaction period. However, the intensity of the 420 nm peak formed after UV exposure varied depending on the solvent chain length. Solvents with longer alkyl chains showed higher 420 nm peak intensity, with HDO exhibiting the highest intensity, followed by TDO and DO. This suggests that the chain length of the solvent plays a role in stabilizing the tungsten oxide-solvent complex, enhancing its interaction with UV light. Despite these differences in UV-visible properties, the IR spectra remained consistent across all solvents, indicating that the chain length did not significantly alter the core chemical transformation, leading to tungsten oxide formation.

[0079] As displayed in Figs. 8A-8B, the XRD analysis confirmed the presence of sub- stoichiometric tungsten oxides, specifically W5O14, W20O58 and W18O49, in the analyzed sample. The diffraction pattern clearly shows characteristic peaks corresponding to these oxides. Additionally, peaks attributed to hexadecanol were identified, confirming its incorporation into the material. Peaks corresponding to unreacted tungsten hexacarbonyl were also observed, indicating that not all of the precursor underwent reaction.

[0080] Additional observations. Further examination of different functional groups, including sulfur (1 -hexadecanethiol), amine (1 -hexadecylamine) and phosphate (1- hexadecylphosphonic acid) moieties, revealed that the nature of the moiety is critical for the formation of photochromic tungsten oxide. In all cases, the use of solvents containing these functional groups resulted in products that did not form the blue phase of tungsten oxide and showed no IR absorbance. Additionally, no peak at 420 nm was generated when the products were exposed to UV radiation, and no enhancement in IR behavior was observed.

[0081] These results suggest that sulfur, amine, and phosphate moieties do not provide the necessary stabilization or interaction to support the formation of photochromic tungsten oxide. This emphasizes the importance of carefully selecting solvent structures and functional groups when designing reactions for materials with advanced optical properties.

[0082] Effect of copper salt addition on IR behavior. The objective was to investigate the impact of copper salt (CuCh 2H2O) addition on the IR behavior of tungsten oxide formation in a 100% 1 -hexadecanol (HDO) solvent.

[0083] Procedure: The experiment involved reacting 200 mg of W(CO)e in three separate vials containing 4 g of HDO solvent. Copper chloride (CuCh 2H2O) was added at differentECOG-OOl PCT stages of the reaction: (1) at the start (0 minutes) - immediately after adding W(CO)e to the solvent at 100°C, when the solvent had fully melted; (2) at the mid-reaction (10 minutes) - after 10 minutes of heating in the oil bath; and (3) at the end of the reaction (15 minutes) - near the final stages of the reaction. The reaction was initiated by heating the solvent to 100°C to ensure complete melting and uniform dispersion of W(CO)e. The mixture was then transferred to a preheated 190°C oil bath, where the reaction continued for 20 minutes. During the process, the vials were periodically shaken to promote uniform mixing and prevent reactants from adhering to the vial walls.

[0084] Results: The addition of copper chloride (CuCh 2H2O) at different reaction stages significantly influenced both the reaction dynamics and the resulting IR properties, as demonstrated in Figs. 9A-9C. 0-Minute addition: Introducing copper chloride at the start of the reaction resulted in a twofold (x2) increase in IR intensity after 10 minutes of UV exposure. 10-Minute addition: Adding copper chloride 10 minutes into the reaction led to a 1.6-fold (x1.6) enhancement in IR intensity post-UV exposure. Notably, this timing produced materials with superior IR properties both before and after UV exposure. 15- Minute addition: Copper chloride addition at the 15-minute mark yielded the most substantial enhancement, with a fourfold (z4) increase in IR intensity following UV exposure. These observations suggest that the timing of copper salt addition affects the incorporation and distribution of copper within the tungsten oxide matrix, thereby influencing the material’s IR behavior.

[0085] Proposed mechanisms: Early addition (0 minutes)'. Introducing copper chloride at the onset may lead to the formation of separate copper-containing phases, resulting in less effective integration into the tungsten oxide lattice (Kaban et al.. 2012). Mid-reaction addition (10 minutes)'. Adding copper chloride during the reaction allows for better incorporation into the developing tungsten oxide structure, enhancing IR properties (Migas el al.. 2010). Late addition (15 minutes) '. Copper chloride added at later stages likely results in surface adsorption onto pre-formed tungsten oxide, leading to significant IR intensity increases due to surface interactions (Roman etal., 2024).

[0086] The next section presents further studies involving the physical mixing of preformed tungsten and copper oxide synthesized under similar conditions to validate these hypotheses.ECOG-OOl PCT

[0087] Effect of copper salt-to-tungsten oxide nanowires ratio. The objective was to investigate the influence of copper salt (CuCh 2H2O) on the properties and behavior of tungsten oxide nanowires in 100% HDO solvent at varying copper-to-tungsten ratios.

[0088] Procedure: Two initial reaction mixtures were prepared: (1) Tungsten reaction: 4 g of HDO was heated in a 100°C oil bath, followed by adding W(CO)e. The mixture was then transferred to a 200°C oil bath for a 20-minute reaction. (2) Copper reaction: A second vial containing 4 g of HDO was heated to 100°C, and CuCh 2H2O was added. The reaction was similarly carried out at 200°C for 20 minutes. After completing these reactions, six copper- to-tungsten mixtures were prepared: 100% W, 100% Cu, Cu 10:90 W, Cu 25:75 W, Cu 50:50 W, and Cu 75:25 W. These combinations were analyzed to study the influence of copper content on the optical and IR behavior of the resulting Cu-W oxide nanostructures.

[0089] Observations and results: As demonstrated in Figs. 10A-10F, the 100% tungsten oxide behaved as expected, showing characteristic IR absorption properties with strong UV activity. 100% Copper oxide did not exhibit significant IR properties and displayed a UV peak at approximately 320 nm. Cu-W mixtures: When tungsten oxide and copper products were mixed, the optical properties of the system changed markedly. Key findings include: (1) IR Properties: IR absorption increased with copper content up to a threshold of 25% Cu. Beyond this point, the IR absorption plateaued or declined, suggesting a critical limit for copper’s role in enhancing IR properties. (2) UV Properties: UV absorption increased with copper addition but decreased when copper content exceeded 25%, likely due to structural changes that reduced electronic coupling. Interestingly, despite the dilution of tungsten oxide when mixed with copper, the IR intensity of the mixtures remained higher than that of pure tungsten oxide. This suggests a synergistic interaction between copper and tungsten that enhances IR properties, even when tungsten content is reduced.

[0090] Background and rationale for adding copper. Incorporating copper into tungsten oxide matrices has been demonstrated to enhance their IR absorption properties. Studies have shown that copper-doped tungsten oxide nanocrystals exhibit increased light absorption across the spectrum, with optimal IR absorption at specific copper doping levels (Jeem et al., 2023). Additionally, the interaction between copper and tungsten modifies the structural and electronic properties of the composite material, leading to improved optical behaviors (Si et al., 2011).ECOG-OOl PCT

[0091] This synergy is attributed to copper’s ability to alter the electronic band structure of tungsten oxide, facilitating enhanced coupling between the two elements. The observed effects provide a strong rationale for investigating the influence of copper on tungsten oxide nanostructures under controlled reaction conditions and varying copper-to-tungsten ratios.

[0092] Building on this rationale, our experiments explored how different copper-to- tungsten ratios influence the optical and IR properties of the resulting Cu-W oxide nanostructures. The findings indicate that copper acts as a catalytic enhancer when used in appropriate amounts, optimizing the material’s optical performance. The detailed analysis of these effects is presented in the results section and supported by the accompanying figures. These results align with the literature and expand our understanding of the synergistic interaction between copper and tungsten.Study 2. Masterbatch formation, cover film production, and greenhouse results

[0093] Formation of the masterbatch (MB). The masterbatch (MB) was developed as a critical intermediate to incorporate tungsten oxide nanostructures into polyethylene (PE). Paraffin oil was used to enhance the adhesion of the tungsten oxide powder to the PE surface, ensuring uniform dispersion and preventing agglomeration within the polymer matrix. This step was essential to maintain the functional properties of the tungsten oxide.

[0094] Multiple grades of PE, including PE 320, PE 4023, and PE 100, were utilized in the MB preparation to ensure compatibility with various processing conditions and applications. These grades were selected based on their thermal stability and melt flow index, which are critical for achieving optimal extrusion performance.

[0095] The extrusion process for MB formation was conducted at temperatures ranging from 120°C to 220°C. This wide processing window allowed for flexibility across different PE grades while preserving the photochromic and IR properties of the tungsten oxide nanostructures. During the extrusion process, the paraffin oil facilitated the uniform integration of tungsten oxide into the polymer matrix.

[0096] The resulting MB retained the characteristic photochromic behavior of tungsten oxide. When exposed to sunlight, the material exhibited a blue-to-green color change, which reverted to blue without light. This transformation correlated with a significant enhancement in IR absorption, indicating the MB ’ s suitability for use in advanced greenhouse cover films.ECOG-OOl PCT

[0097] Production of cover films. The MB was used to produce greenhouse cover films through the film-blowing technique. Tungsten oxide loadings in the films ranged from 0.001% to 20% by weight, depending on the desired application. The films produced from the MB demonstrated consistent optical and thermal properties, ensuring scalability and reliability for industrial use.

[0098] The cover films exhibited photochromic behavior, dynamically adjusting their optical properties under varying sunlight conditions. The blue-to-green color change of the tungsten oxide nanostructures enhanced the films’ IR absorption, providing dynamic heat regulation for greenhouses. The films also maintained high visible light transmittance, crucial for supporting plant photosynthesis and growth, as demonstrated in Fig. 11.

[0099] Greenhouse testing and temperature reduction results. The performance of the tungsten oxide-infused films was tested in small-scale greenhouse models. Two greenhouses (60 cm x 60 cm x 120 cm) were constructed for comparison: (1) Reference greenhouse'. Covered with a standard 150-micrometer PE film; and (2) Test greenhouse'. Covered with a PE film containing tungsten oxide at 0.04% by weight.

[0100] As shown in Fig. 12, the test greenhouse significantly improved internal temperature regulation. Over a 48-hour monitoring period, the tungsten oxide-infused film reduced the internal temperature by approximately 2°C compared to the reference greenhouse (Figs. 13A-13C). Further testing was conducted with a higher tungsten oxide concentration of 0.1% by weight. In this extended 6-day experiment, the test greenhouse achieved even more significant temperature reductions, ranging from 5°C to 9°C during peak noon conditions (Fig. 14).ECOG-OOl PCTREFERENCESDeb, S.K., Opportunities and challenges in science and technology of WO3 for electrochromic and related applications. Solar Energy Materials and Solar Cells, 2008, 92(2), 245-258Jeem, M. et al., Defect-driven opto-critical phases tuned for all-solar utilization. Adv Mater. 2023, 35(46), 2305494.Kaban, I. et al, Phase separation in monotectic alloys as a route for liquid state fabrication of composite materials. Journal of Materials Science, 2012, 47, 8360-8366Migas, D.B. et al., Tungsten oxides. I. Effects of oxygen vacancies and doping on electronic and optical properties of different phases of WO3. Journal of Applied Physics, 2010, 108(9), 093713Moshofsky, B., Mokari, T., Length and diameter control of ultrathin nanowires of substoichiometric tungsten oxide with insights into the growth mechanism. Chemistry of Materials, 2013, 25(12), 2618-2628Moshofsky, B.; Mokari, T., Electrochromic active layers from ultrathin nanowires of tungsten oxide. J. Mater. Chem. C, 2014, 2, 3556Roman, B.J. et al., Tunable optical response of plasmonic metal oxide nanocrystals. MRS Bulletin, 2024, 49, 1032-1044Si, Z. et al., Synergistic effects between copper and tungsten on the structural and acidic properties of CuCMWOv-ZrCb catalyst. Catalysis Science & Technology, 2011, 3Sun, M. etal., Nanocrystalline tungsten oxide thin film: Preparation, microstructure, and photochromic behavior. Journal of Materials Research, 2000, 15(4), 927-933

Claims

ECOG-OOl PCTCLAIMS1. A process for the preparation of a photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides coated with at least one alkanol containing at least 7 carbon atoms; and an inorganic complex of tungsten and said at least one alkanol, said process comprising:(i) introducing tungsten hexacarbonyl (W(CO)e), optionally in the form of a powder, into a liquid medium comprising said at least one alkanol, to thereby obtain a reaction mixture;(ii) heating the reaction mixture at a temperature higher than the melting temperature of said at least one alkanol but not higher than 100°C, while stirring, under ambient pressure, for a period of from a few seconds up to about 10 minutes, to thereby facilitate mixing of said tungsten hexacarbonyl and said at least one alkanol;(iii) heating the reaction mixture thus obtained at a temperature from about 150°C to about 200°C, for a period not exceeding 60 minutes, while said reaction mixture is covered, to thereby facilitate partial oxidation of said tungsten hexacarbonyl and consequently obtain said nanostructures; and(iv) fast cooling the reaction mixture thus obtained to a temperature lower than 100°C, e.g., room temperature, wherein the color of said reaction mixture during the heating step (iii) first becomes yellow, and then gradually changes from yellow to green and from green to blue as said heating proceeds, and wherein the cooling step (iv) is initiated not before the color of said reaction mixture is purely green; and in case the color of said reaction mixture is purely blue, as long as upon exposure to UV irradiation, said mixture reaction exhibits a photochromic shift from blue to green.

2. The process of claim 1, wherein the amount of said inorganic complex in said composition is at its maximum at a stage wherein the color of the reaction mixture has completely changed from yellow to green, and decreases as the color of said reaction mixture gradually changes from green to blue; and wherein the intensity of the peak at 420 nm in the UV-Vis spectrum is in positive correlation with the amount of said inorganic complex in said composition.ECOG-OOl PCT3. The process of claim 1, wherein:(a) the cooling step (iv) is initiated at a stage wherein the color of said reaction mixture is purely green; and upon exposure to UV irradiation, said composition consequently exhibits a peak at 420 nm in the UV-Vis spectrum and a spontaneous reversible photochromic shift from light green to strong yellow; or(b) the cooling step (iv) is initiated at a stage wherein the color of said reaction mixture is either blue or in a phase of changing from green to blue; and upon exposure to UV irradiation, said composition consequently exhibits a peak at 420 nm in the UV-Vis spectrum, a spontaneous reversible photochromic shift from blue to green, and an enhanced infrared (IR) absorption (increased IR responsiveness).

4. The process of claim 1, wherein said sub-stoichiometric tungsten oxides are selected from WO2.625 (W32O84; W3O8), WO2.725 (W18O49), WO2.785 (W17O47), WO2.8 (W5O14), WO2.9 (W20O58), and WO2.92 (W25O73).

5. The process of claim 4, wherein said sub-stoichiometric tungsten oxides comprise at least one of W5O14, W20O58, W18O49, and W25O?3, preferably each one of W5O14, W20O58, W18O49, andW25O?3.

6. The process of any one of claims 1-5, wherein said at least one alkanol each independently is (Cio-C22)alkanol such as 1-decanol, 1-dodecanol (lauryl alcohol), 1- tetradecanol (myristyl alcohol), 1 -hexadecanol (cetyl alcohol), 1 -octadecanol (stearyl alcohol), 1-eicosanol (arachidyl alcohol), and 1 -docosanol (behenyl alcohol).

7. The process of claim 6, wherein said alkanol is 1 -hexadecanol.

8. The process of any one of claims 1-7, wherein said liquid medium has been prepared by heating said at least one alkanol to a temperature above its melting point.

9. The process of claim 8, wherein said at least one alkanol is 1 -hexadecanol, and said liquid medium has been prepared by heating 1 -hexadecanol to a temperature above 50°C.

10. The process of any one of claims 1 -9, wherein said tungsten hexacarbonyl constitutes from about 1.25% to about 20% by weight of said reaction mixture.ECOG-OOl PCT11. The process of any one of claims 1-10, wherein said at least one alkanol is 1- hexadecanol; and said reaction mixture is heated in step (ii) at a temperature of about 80°C, preferably for a period of about 5 minutes.

12. The process of any one of claims 1-11, wherein said heating in step (iii) is carried out for about 20 minutes.

13. The process of any one of claims 1-10, wherein said liquid medium further comprises a mineral oil or a component thereof, and said at least one alkanol constitutes at least 5% by weight of said liquid medium.

14. The process of claim 13, wherein the weight ratio between said at least one alkanol and said mineral oil or component thereof in said liquid medium is from about 3:1 to about 1 :3, respectively.

15. The process of claim 13 or 14, wherein said mineral oil or component thereof is (C7- C2o)alkane.

16. The process of claim 15, wherein said alkanol is 1 -hexadecanol; and said mineral oil or component thereof is hexadecane.

17. The process of any one of claims 1-16, wherein the cooled reaction mixture obtained is in the form of a solid or semi-solid, and said process further comprises the step of: (v) grinding the solidified reaction mixture to fine powder.

18. A photochromic tungsten oxide composition comprising (a) nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides coated with at least one alkanol containing at least 7 carbon atoms; and (b) an inorganic complex of tungsten and said at least one alkanol.

19. The photochromic tungsten oxide composition of claim 18, wherein upon exposure to UV irradiation, said composition exhibits a peak at 420 nm in the UV-Vis spectrum; a spontaneous reversible photochromic shift from blue to green; and optionally an enhanced infrared (IR) absorption.ECOG-OOl PCT20. The photochromic tungsten oxide composition of claim 18 or 19, obtained by the process of any one of claims 1-18.

21. A masterbatch comprising a polymer incorporated with a photochromic tungsten oxide composition according to any one of claims 18-20.

22. The masterbatch of claim 21, wherein said polymer is polyethylene.

23. The masterbatch of claim 21 or 22, wherein the sub-stoichiometric tungsten oxides loading in said masterbatch is from about 0.001% to about 20% by weight.

24. The masterbatch of any one of claims 21-23, wherein said nanostructures are evenly dispersed within said polymer.

25. A polyethylene greenhouse cover comprising a masterbatch according to any one of claims 22-24.

26. A non-photochromic tungsten oxide composition comprising nanostructures made of a core comprising a plurality of sub-stoichiometric tungsten oxides coated with at least one alkanol containing at least 7 carbon atoms, obtained by the process of any one of claims 1- 16, wherein the cooled reaction mixture obtained in step (iv) of said process is in liquid form, and has been centrifuged, optionally while washing with an organic solvent to dissolve said at least one alkanol and prevent its solidification, to thereby remove said inorganic complex from the composition, optionally followed by drying.

27. The non-photochromic tungsten oxide composition of claim 26, wherein said organic solvent is a polar organic solvent such as acetic acid, acetone, acetonitrile, dimethylformamide (DMF), dimelthylsulfoxide (DMSO), methanol, ethanol, propanol, isopropanol, butanol, / -butyl alcohol, chlorobenzene, 1,2-di chloroethane, ethylene glycol, diethylene glycol, ethyl acetate, and methylene chloride; a non-polar organic solvent such as hexane, cyclohexane, chloroform, diethyl ether, toluene, xylene, tetrachloroethylene, n- heptane, isooctane, and benzene; or a combination thereof.

28. The non-photochromic tungsten oxide composition of claim 26 or 27, wherein said composition exhibits IR absorption properties that are not enhanced upon exposure to UVECOG-OOl PCT irradiation, but neither a peak at 420 nm in the UV-Vis spectrum nor a spontaneous reversible photochromic shift from blue to green.

29. An article comprising a plastic incorporated with a photochromic tungsten oxide composition according to any one of claims 18-20, or a non-photochromic tungsten oxide composition according to any one of claims 26-28.

30. The article of claim 29, wherein said article is a lens such as a sunglass’ lens.

Images