A nanocomposite material of near-infrared localized surface plasmon resonance nanocrystals and quantum dots and its preparation and application

Abstract

The present invention discloses a nanocomposite material of near-infrared localized surface plasmon resonance nanocrystals and quantum dots and its preparation and application. The method comprises: in a light-shielded state, 2‑x Se@SiO2 nanocrystals in chloroform solution and CuInSe x S 2‑x / ZnS chloroform solution was mixed and stirred, and collected; the Cu 2‑x Se@SiO2 nanocrystal chloroform solution and the CuInSe x S 2‑x The volume ratio of ZnS to chloroform solution is 1:(10-200). The present invention solves the problem of low fluorescence quantum efficiency and poor light / chemical stability in the near-infrared range of the prior art, which limits its development in luminescent solar concentrators. The fluorescence quantum yield of the nanocomposite material prepared by the present invention is about 45%, which is increased by about 84%. It is applied to 2×2×0.3cm 3 The power conversion efficiency of the luminescent solar concentrator is as high as 0.42%.

Description

Technical Field

[0001] The present invention relates to a quantum dot, in particular to a nano-composite material of nanocrystals and quantum dots and the preparation and application thereof. Background Art

[0002] Luminescent solar concentrators (LSCs) technology can be used in conjunction with solar cells. The fluorescent materials doped inside them absorb sunlight, and the fluorescence that meets the total reflection conditions will be concentrated at the edge of the device, which can increase the incident light density received by the photovoltaic device, thereby improving the photoelectric conversion efficiency of the solar cell and reducing energy consumption and power generation costs. At the same time, semi-transparent luminescent solar concentrators can also be used as building materials, such as light-transmitting smart windows, concentrating carports / roofs, etc., combining the characteristics of energy conservation and aesthetics, and have great commercial potential. Generally speaking, a fluorescent material suitable for large-area luminescent solar concentrators should have the following characteristics: (1) a wide absorption spectrum that is compatible with the solar spectrum; (2) a large Stokes shift; (3) a high fluorescence quantum efficiency; (4) good dispersibility and compatibility with the polymer matrix; (5) high light / chemical stability; (6) green and environmentally friendly and low preparation cost. With the recent development and breakthroughs in inorganic semiconductor nanotechnology, a series of inorganic colloidal fluorescent nanomaterials have been successfully synthesized using wet chemical methods. Their absorption, fluorescence spectra, and photochemical stability can be manipulated by selecting the composition, structure, morphology, and size of the materials. Among them, three-dimensional quantum-confined inorganic semiconductor quantum dots (QDs) hold great promise for application in high-efficiency, large-area luminescent solar concentrators due to their wide absorption range, tunable Stokes shift, high fluorescence quantum efficiency, and photochemical stability.

[0003] Over the past two decades, research on inorganic colloidal quantum dots has mainly focused on the ultraviolet-visible spectrum, and most of the high-luminescence fluorescent material quantum dots contain heavy metal elements such as lead and cadmium, which are extremely unfriendly to the environment. However, research on green and environmentally friendly near-infrared quantum dots is not mature enough, especially CuInSe with its unique energy level structure, wide absorption range and adjustable Stokes shift. x S 2-x QDs. To improve CuInSe x S 2-x The fluorescence quantum efficiency and photostability of QDs are improved by coating the surface with ZnS, a material with a wider band gap, to passivate the dangling bonds on the core surface, reduce the defect concentration at the core-shell interface, and reduce the possibility of non-radiative recombination processes, thereby improving its fluorescence quantum efficiency. However, for the quaternary alloy CuInSe with a fluorescence peak of around 900-1000nm, x S 2-xFor Cu / ZnS QDs, their low fluorescence quantum efficiency and poor photo / chemical stability in the near-infrared range further limit their development in luminescent solar concentrators. Based on this, the development and synthesis of green, environmentally friendly, pollution-free, high fluorescence quantum yield near-infrared CuInSe x S 2-x / ZnS QDs is imminent. At present, the relevant research at home and abroad is still focused on the regulation and optimization of its intrinsic optical properties, and the research on near-infrared localized surface plasmon resonance materials and CuInSe x S 2-x There is little research on the influence of plasmon-exciton coupling between ZnS / ZnS quantum dots on the optical properties of quantum dots, which needs further exploration and discovery. Summary of the Invention

[0004] The purpose of the present invention is to provide a nanocomposite material of near-infrared localized surface plasmon resonance nanocrystals and quantum dots and its preparation and application, which solves the problem that the existing technology has low fluorescence quantum efficiency and poor light / chemical stability in the near-infrared range, which limits its development in luminescent solar concentrators.

[0005] In order to achieve the above object, the present invention provides a method for preparing a nanocomposite material of nanocrystals and quantum dots, the method comprising:

[0006] In the dark, Cu 2-x Se@SiO2 nanocrystals in chloroform solution and CuInSe x S 2-x / ZnS chloroform solution was mixed and stirred, and collected to obtain the nanocomposite material; the Cu 2-x Se@SiO2 nanocrystal chloroform solution and the CuInSe x S 2-x The volume ratio of ZnS / chloroform solution is 1:(10-200).

[0007] In the preparation of Cu 2-x Se@SiO2 nanocrystals coupled with CuInSe x S 2-x There are two competing processes in the nanocomposite system of Cu / ZnS quantum dots: direct energy transfer and resonant energy transfer. 2-x When the concentration of Se@SiO2 nanoparticles is high, the direct energy transfer process dominates, so that more electrons in the quantum dots will be transferred to the Cu 2-x Se@SiO2 and non-radiative recombination occurs; when the volume ratio is too small, Cu 2-xWhen the concentration of Se@SiO2 nanoparticles is low, it is not enough to provide sufficient electric field strength to the quantum dots and to some extent inhibits the effective transition of electrons in the quantum dots; all of the above will lead to a decrease in the PL intensity of the quantum dots and quenching. 2-x When the concentration of Se@SiO2 nanoparticles is appropriate, the resonance energy transfer process will dominate and more effectively excite CuInSe x S 2-x / ZnS quantum dots and promote their radiative recombination, resulting in enhanced PL intensity.

[0008] Preferably, the Cu 2-x The absorbance of Se@SiO2 nanocrystal chloroform solution in the localized surface plasmon resonance absorption band is 0.18; the CuInSe x S 2-x CuInSe / ZnS chloroform solution x S 2-x The concentration of ZnS was 0.46 mg / mL.

[0009] Preferably, the CuInSe x S 2-x / ZnS chloroform solution was prepared by the following method:

[0010] (1) dissolving cuprous iodide and indium acetate in a mixture of dodecanethiol and oleylamine, degassing under vacuum at 90°C, raising the temperature to 140°C under nitrogen protection and stirring to fully dissolve, heating the temperature to 180-230°C (not equal to 230°C), injecting dodecanethiol / oleylamine-selenium solution, then heating to 230°C for reaction, and then injecting ZnS precursor for reaction;

[0011] (2) After the reaction is completed, cool to 60-80°C, centrifuge and purify with chloroform and acetone, and disperse in chloroform to obtain CuInSe x S 2-x / ZnS chloroform solution.

[0012] More preferably, the dodecanethiol / oleylamine-selenium solution is prepared by mixing selenium powder, oleylamine and dodecanethiol under nitrogen atmosphere at room temperature; the ZnS precursor is prepared by dissolving zinc stearate in a mixture of octadecene, oleic acid and dodecanethiol, degassing under vacuum at 80°C, and heating to 150°C.

[0013] Preferably, the Cu 2-x Se@SiO2 nanocrystal chloroform solution was prepared by the following method:

[0014] (1) Disperse the surfactant in cyclohexane, add ethyl orthosilicate, ammonia solution and Cu 2-xSe chloroform solution was stirred continuously in the dark; after the reaction was completed, ethanol was added and centrifuged to separate Cu 2-x Se@SiO2 nanocrystals, Cu 2-x Se@SiO2 nanocrystals were dispersed in anhydrous ethanol and aged to obtain Cu 2-x Se@SiO2 ethanol solution;

[0015] (2) Cu 2-x Se@SiO2 ethanol solution was mixed with ammonia water to adjust the pH value to alkaline, and octadecyltrimethoxysilane chloroform solution was added under stirring at a speed of 800-1000 rpm / min. The reaction was continued by stirring at a speed of 800-1000 rpm / min (slow stirring speed may cause incomplete mixing of octadecyltrimethoxysilane chloroform solution and stratification). After that, the mixture was purified by centrifugation with ethanol and dispersed in chloroform to obtain the Cu@SiO2 solution. 2-x Se@SiO2 nanocrystals in chloroform solution.

[0016] The Cu 2-x The concentration of Se chloroform solution was 1.6 mg / mL. 2-x During the process of Se@SiO2 nanocrystals, Cu 2-x The concentration of Se is a key factor. If the concentration is too low, SiO2 will form a single nucleus. If the concentration is too high, multiple Cu2 will appear in one SiO2. -x Se nanoparticles, making the coating uneven.

[0017] Preferably, the surfactant is polyoxyethylene nonylphenyl ether; the Cu 2-x The absorbance of Se@SiO2 ethanol solution in the localized surface plasmon resonance absorption band is 0.21. 2-x Se@SiO2 chloroform solution, Cu 2-x The concentration of Se@SiO2 ethanol solution is qualitatively expressed by the absorbance. Generally speaking, the greater the sample absorbance, the greater its relative concentration. 2-x Se@SiO2 chloroform solution and Cu 2-x The absorbance of Se@SiO2 ethanol solution is high, that is, the relative concentration is high. Due to the strong non-radiative energy transfer of the localized surface plasmon resonance absorption band, the direct energy transfer process is dominant, resulting in the fluorescence quenching of the nanocomposite material. 2-x Se@SiO2 chloroform solution and Cu 2-x The absorbance of Se@SiO2 ethanol solution is relatively low, that is, the relative concentration is low. The low electric field effect of the localized surface plasmon resonance absorption band is not enough to compensate for the concentration dilution effect in the nanocomposite material, which will also lead to fluorescence quenching.

[0018] Preferably, the Cu 2-x Se chloroform solution is prepared by mixing cuprous chloride powder with oleylamine, degassing at 110°C, heating to 225°C, injecting oleic acid-selenium precursor when the solution turns into a transparent dark yellow, lowering the temperature to 205°C and maintaining it at 205°C, then cooling to 60°C, adding ethanol, centrifuging and purifying, and dispersing it in chloroform to obtain Cu 2-x Se chloroform solution.

[0019] In the preparation of Cu 2-x During the process of Se deposition, the injection temperature of oleic acid-selenium precursor (225℃) is a key factor that will directly affect the Cu 2-x The size of Se nanoparticles and the peak position of the localized surface plasmon resonance (LSPR) absorption band are affected. If the temperature is too high, Cu 2-x Se particles are large in size, and the LSPR absorption band peak will red-shift to 1300-1600 nm. Its vibration frequency will not fall within the absorption / fluorescence spectrum of quantum dots, and the increase in local electric field strength will not increase the absorption cross-section coefficient and fluorescence radiation recombination rate of quantum dots.

[0020] More preferably, the oleic acid-selenium precursor is prepared by dissolving selenium powder in oleic acid, evacuating the mixture at 90°C, heating the mixture to 220°C and then to 280°C under a nitrogen atmosphere until the solution becomes a yellow transparent clear liquid.

[0021] When preparing the oleic acid-selenium precursor, the reaction temperature of 280°C is a key factor. If the reaction temperature is lower than 280°C, selenium will not be completely dissolved and will aggregate in the oleic acid, resulting in a low actual concentration of the oleic acid-selenium precursor and an inability to react with cuprous chloride to form cuprous selenide.

[0022] The present invention provides a nanocomposite material prepared by the preparation method.

[0023] Preferably, the nanocomposite material is a core-shell structure, wherein the core is Cu 2-x Se@SiO2 nanocrystals with CuInSe shell x S 2-x / ZnS quantum dots; the CuInSe x S 2-x / ZnS quantum dots and Cu 2-x The electrostatic attraction on the surface of Se@SiO2 nanocrystals x S 2-x / ZnS quantum dots are uniformly adsorbed on Cu 2-x The surface of Se@SiO2 nanocrystals; the Cu 2-x Se@SiO2 nanocrystals are based on Cu 2-xSe nanoparticles are the core and SiO2 is coated on the outside of the core-shell structure, where the thickness of the SiO2 shell is about 10.5nm. The SiO2 shell can not only act as a passivation layer to protect Cu 2-x Se nanocrystals can also be used to regulate Cu 2-x Se nanocrystals and CuInSe x S 2-x / ZnS quantum dots, the dielectric layer between Cu 2-x Se nanocrystals and CuInSe x S 2-x / ZnS quantum dots play an important role in energy transfer. If the thickness of the SiO2 shell is too small, for example, the minimum thickness, that is, the SiO2 shell thickness is 0nm, due to the Cu 2-x The strong field effect of localized surface plasmon resonance in Se induces the dominance of non-radiative direct energy transfer, resulting in more electrons in the quantum dots being transferred to Cu. 2-x Se nanocrystals and fluorescence quenching occurs; if the thickness of the SiO2 shell is too large, the Cu 2-x The resonance energy transfer efficiency of Se nanocrystals leads to fluorescence quenching of the nanocomposite material; only when the SiO2 shell thickness is 10.5nm, it exhibits the strongest fluorescence emission intensity, higher fluorescence quantum yield and extended fluorescence lifetime.

[0024] The present invention provides an application of the nanocomposite material in the field of luminescent solar concentrators.

[0025] The nanocomposite material of nanocrystals and quantum dots of the present invention, as well as its preparation and application, solves the problems of low fluorescence quantum efficiency and poor light / chemical stability in the near-infrared range in the prior art, which limit its development in luminescent solar concentrators, and has the following advantages:

[0026] 1. The present invention is based on Cu 2-x In the preparation of Se chloroform solution, centrifugation was first performed at 4000 rpm for 1 min, and the supernatant was adjusted to 8000 rpm and centrifuged for 1 min. This not only greatly saved the time of centrifugal purification, but also achieved better purification effect. 2-x In the preparation of Se@SiO2, the reverse microemulsion method is used. It only takes one day to achieve the coating of silica, which greatly saves experimental time and improves experimental efficiency. In addition, the problems in the prior art will not occur during the coating process (the prior art usually uses the Stoeber method to coat silica on cuprous selenide, which takes three days to achieve the coating of silica. Due to the instability of cuprous selenide, it will be oxidized during the reaction or directly etched by the reaction solution, resulting in the disappearance of the LSPR peak. In addition, silica will usually hydrolyze and condense itself to form nuclei alone or on the surface of Cu.2-x Se surface sticks and aggregates instead of forming Cu with clear core-shell boundary. 2-x Se@SiO2 core-shell structure), the absorption after coating can be seen from the absorption spectrum and LSPR absorption band can be observed. The core-shell structure can be seen from TEM that its boundaries are clear and the particle size is uniform; in CuInSe x S 2-x In the preparation of ZnS, only one ZnS precursor needs to be prepared and one injection is completed during the coating process, so the preparation method is simpler.

[0027] 2. The present invention uses near-infrared non-noble metal nanomaterials cuprous selenide and CuInSe with localized surface plasmon resonance effect (LSPR) x S 2-x / ZnS quantum dots are coupled to form a composite system. The distance between the two is regulated by silicon dioxide (SiO2) to enhance the local electromagnetic field and energy transfer capabilities, increase the absorption cross-section coefficient of the quantum dots and the fluorescence radiation recombination rate, thereby improving the light absorption capacity and photoelectrochemical properties of the quantum dots. The fluorescence quantum yield of the prepared nanocomposite material is increased by about 84%, and the fluorescence intensity can still maintain about 53% after continuous ultraviolet irradiation for 2 hours.

[0028] 3. The nanocomposite material prepared by the present invention is applied in 2×2×0.3cm 3 The power conversion efficiency (PCE) of the luminescent solar concentrator is as high as 0.42%, and the external quantum efficiency (η ext ) as high as 2.63%. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Prepare a roadmap for embodiments of the present invention;

[0030] Figure 2 The Cu prepared in Example 1 of the present invention 2-x Transmission electron microscopy image of Se@SiO2 nanocrystals;

[0031] Figure 3 CuInSe prepared in Example 1 of the present invention x S 2-x / Transmission electron microscopy image of ZnS quantum dots;

[0032] Figure 4 This is a transmission electron microscope image of sample 1 prepared in Example 1 of the present invention;

[0033] Figure 5 Sample 1, Cu, obtained in Example 1 of the present invention 2-x Se@SiO2 nanocrystals and CuInSe x S 2-xUV-visible-near-infrared absorption spectrum of / ZnS;

[0034] Figure 6 This is a comparison chart of fluorescence enhancement factor curves of the materials prepared in Example 1, Example 2, and Example 3 of the present invention;

[0035] Figure 7 This is a comparison chart of the near-infrared fluorescence spectra of the materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0036] Figure 8 1 is a comparison chart of the fluorescence lifetimes of the materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention;

[0037] Figure 9 The current density-voltage (JV) curves of the materials prepared in Example 1 and Comparative Example 1 of the present invention when applied to luminescent solar concentrators of different areas;

[0038] Figure 10 This is a comparison chart of the light stability of the materials prepared in Example 1 of the present invention and Comparative Example 1 when used in a luminescent solar concentrator. DETAILED DESCRIPTION

[0039] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0040] Example 1

[0041] A new type of LSPR non-noble metal Cu 2-x Se@SiO2 nanocrystals and quaternary alloy CuInSe x S 2-x A method for preparing a ZnS / ZnS quantum dot nanocomposite material, the method comprising:

[0042] (1) 0.079 g of selenium powder was dissolved in 10 mL of oleic acid, and the mixture was vacuumed at 90 °C for 30 min. The mixture was heated to 220 °C under nitrogen atmosphere and reacted for 10-15 min. The mixture was then immediately heated to 280 °C and reacted for 25 min. The solution gradually turned into a yellow transparent clear liquid, indicating that an OA-Se precursor was formed (after cooling to room temperature, the OA-Se precursor turned into a gel-like state, which should be heated to make it liquid before use).

[0043] (2) 0.049 g of cuprous chloride powder was mixed with 10 mL of oleylamine and degassed at 110 °C for 30 min. The solution was then heated to 225 °C. When the solution turned into a transparent dark yellow, an organic copper precursor solution was obtained. 5 mL of OA-Se precursor was injected into the obtained organic copper precursor solution (at 225 °C, oleic acid-selenium precursor was extracted with a syringe and injected into a three-necked flask). The temperature was lowered to 205 °C and maintained at 205 °C for 2.5 min. The temperature was then lowered to 60 °C. Ethanol was added to the reaction solution and centrifuged for purification to obtain Cu 2-x Se nanoparticles were dispersed in chloroform to obtain Cu 2-x Se chloroform solution.

[0044] (3) 1.3 mL of polyoxyethylene nonylphenyl ether (IGEPAL CO-520) surfactant was dispersed in 10 mL of cyclohexane, and then 80 μL of TEOS, 150 μL of ammonia solution and 100 μL of Cu prepared in step (2) were added. 2-x Se chloroform solution was stirred continuously in the dark for 24 hours; after the reaction, ethanol was added and centrifuged repeatedly to separate Cu from the microemulsion. 2-x Se@SiO2 nanocrystals, Cu 2-x Se@SiO2 nanocrystals were dispersed in anhydrous ethanol and aged for 3 to 5 days to obtain Cu 2-x Se@SiO2 ethanol solution.

[0045] (4) 10 mL Cu 2-x Se@SiO2 ethanol solution was mixed with 0.1 mL ammonia water to adjust the pH value to alkaline (pH value 9), and 1 mL octadecyltrimethoxysilane chloroform solution was added under stirring at a speed of 800-1000 rpm / min. The reaction was continued at a speed of 800-1000 rpm / min and stirred for 24 hours. After that, the mixture was purified by centrifugation with ethanol and dispersed in chloroform to obtain Cu 2-x Se@SiO2 nanocrystals in chloroform solution.

[0046] (5) 0.158 g of selenium powder was mixed with 1.5 mL of oleylamine and 0.5 mL of dodecanethiol to prepare a 1 M OLA / DDT-Se solution at room temperature under nitrogen atmosphere. 6.32 g of zinc stearate was dissolved in a mixture of 20 mL of octadecene, 10 mL of oleic acid and 10 mL of dodecanethiol, and the mixture was vacuum degassed at 80 °C for 30 min. The mixture was heated to 150 °C for 10 min to prepare a ZnS precursor. The temperature was maintained at 50 °C and stirred continuously for use.

[0047] (6) 0.19 g of cuprous iodide and 0.29 g of indium acetate were dissolved in a mixture of 5 mL of dodecanethiol and 1 mL of oleylamine, and vacuum degassed at 90 ° C for 30 min; then the temperature was raised to 140 ° C under nitrogen protection until all the solid precursors were completely dissolved, and the temperature was continued to be heated to 180 ° C, and the 1 M OLA / DDT-Se solution prepared in step (5) was injected to react for 10 min, and then the temperature was raised to 230 ° C to react for 20 to 40 min, and 10 mL of the ZnS precursor solution prepared in step (5) was injected into the reaction mixture to react for 2 h; after the reaction was completed, it was quickly cooled to 60 to 80 ° C in an ice water bath, and then centrifuged and purified by chloroform and acetone to obtain CuInSe x S 2-x / ZnS quantum dots, and finally CuInSe x S 2-x / ZnS quantum dots dispersed in chloroform to obtain CuInSe x S 2-x / ZnS chloroform solution.

[0048] (7) In a dark state, the Cu prepared in step (4) 2-x Se@SiO2 nanocrystal chloroform solution and CuInSe prepared in step (6) x S 2-x The Cu / ZnS chloroform solution was mixed and stirred at a volume ratio of 1:16 for 5 h, and then collected to obtain Cu 2-x Se@SiO2-CuInSe x S 2-x / ZnS nanocomposite material, recorded as sample 1.

[0049] like Figure 1 As shown, the embodiment of the present invention prepares a roadmap. Figure 1 It can be seen that a layer of silicon dioxide is coated on the surface of cuprous selenide to regulate the interaction between cuprous selenide and CuInSe x S 2-x / ZnS quantum dots, using a self-assembly adsorption strategy, using CuInSe x S 2-x / ZnS quantum dots and Cu 2-x The electrostatic attraction on the surface of Se@SiO2 nanoparticles x S 2-x / ZnS quantum dots are uniformly adsorbed on Cu 2-x A novel environmentally friendly near-infrared LSPR Cu was synthesized on the surface of Se@SiO2 2-x Se@SiO2-CuInSe x S 2-x / ZnS nanocomposite materials.

[0050] Comparative Example 1

[0051] The preparation method of an uncoupled quantum dot nanomaterial is basically the same as that in Example 1, except that:

[0052] There are no steps (1) to (4), and in step (7), Cu 2-x Se@SiO2 nanocrystal chloroform solution was replaced with the same volume of CuInSe x S 2-x / ZnS chloroform solution, and the same operation as in Example 1 was performed to obtain uncoupled CuInSe x S 2-x / ZnS quantum dot nanomaterial is recorded as comparative sample 1.

[0053] Comparative Example 2

[0054] The preparation method of a quantum dot nanocomposite material is basically the same as that in Example 1, except that:

[0055] There are no steps (3) to (4), and in step (7), Cu 2-x Se@SiO2 nanocrystal chloroform solution was replaced with the same volume of Cu 2-x Se chloroform solution, and the same operation as in Example 1 was performed to prepare a nanocomposite material, which was designated as Comparative Sample 2 (CuInSe x S 2-x / ZnS and Cu 2-x Se coupling).

[0056] Example 2

[0057] A new type of LSPR non-noble metal Cu 2-x Se@SiO2 nanocrystals and quaternary alloy CuInSe x S 2-x The preparation method of the ZnS quantum dot nanocomposite material is basically the same as that in Example 1, except that:

[0058] In step (7), Cu 2-x Se@SiO2 nanocrystals in chloroform solution and CuInSe x S 2-x The volume ratio of ZnS to ZnS chloroform solution was adjusted from 1:16 to 1:200, and the same operation as in Example 1 was performed to obtain a nanocomposite material, which was designated as Sample 2.

[0059] Example 3

[0060] A new type of LSPR non-noble metal Cu 2-x Se@SiO2 nanocrystals and quaternary alloy CuInSe x S 2-xThe preparation method of the ZnS quantum dot nanocomposite material is basically the same as that in Example 1, except that:

[0061] In step (7), Cu 2-x Se@SiO2 nanocrystals in chloroform solution and CuInSe x S 2-x The volume ratio of ZnS / ZnS chloroform solution was adjusted from 1:16 to 1:10, and the same operation as in Example 1 was performed to obtain a nanocomposite material, which was designated as Sample 3.

[0062] Experimental Example 1 Characterization

[0063] 1. Electron microscope image

[0064] like Figure 2 As shown, the Cu prepared in Example 1 of the present invention 2-x Transmission electron microscope image of Se@SiO2 nanocrystals. Figure 2 It can be clearly observed that Cu 2-x The core is made of Se nanoparticles and SiO2 is coated on the outside of the core-shell structure. The shell thickness is about 10.5nm. The SiO2 dielectric layer can not only passivate and protect the unstable Cu 2-x Se nanoparticles can also inhibit Cu 2-x The strong LSPR effect of Se can effectively prevent the quantum dots from moving toward Cu 2-x The energy transfer of Se core promotes the fluorescence enhancement effect of localized surface plasmon resonance quantum dots.

[0065] like Figure 3 As shown, the CuInSe prepared in Example 1 of the present invention x S 2-x Transmission electron microscope image of / ZnS quantum dots. Figure 3 It is shown in the figure that CuInSeS / ZnS quantum dots have a uniform and monodisperse tetrahedral "pyramid" structure with an average size of about 8.0 nm and a shell ZnS thickness of about 0.23 nm.

[0066] like Figure 4 As shown in FIG, the transmission electron microscope image of sample 1 prepared in Example 1 of the present invention. Figure 4 As can be seen, sample 1 is monodispersed as a whole, and the quantum dots are adsorbed on Cu 2-x Se nanoparticles are surrounded by SiO2 layers and clearly separated, showing a structure similar to a "sunflower". 2-x Nonspecific binding between Se nanoparticles, CuInSe x S 2-x The self-assembly adsorption ability of ZnS quantum dots on the silica shell is enhanced.

[0067] 2. Near-infrared characterization

[0068] UV-visible near-infrared absorption spectra were tested using a Shimadzu UV-3600i plus spectrophotometer. Before the test, a blank reagent chloroform solution was used to subtract the background. At the same time, all samples were dispersed in chloroform and the absorbance was measured in a quartz cuvette with a path length of 1 cm. The photoluminescence quantum yield was measured using an Edinburgh FluoroLog-3 fluorescence spectrometer equipped with a xenon lamp, a monochromator for steady-state fluorescence excitation, and a single photon counting unit for time-resolved correlation coupled to a pulsed laser diode. CuInSe was measured using a calibrated integrating sphere. x S 2-x The fluorescence quantum yield of the unknown sample can be determined by the following formula:

[0069]

[0070] Wherein, the subscripts S and R represent the sample and reference, respectively, and Φ R is the quantum yield of the reference standard, Φ S is the quantum yield of the sample, I is the integrated intensity of the fluorescence spectrum (generally refers to photoluminescence), and the fluorescence term I S / I R It is the ratio of the fluorescence photon number of the sample and the reference standard solution, that is, the ratio of the fluorescence integrated intensity of the sample and the reference solution. A is the fluorescence intensity of the solution at the excitation wavelength (λ Ex ), n is the refractive index of the solvent.

[0071] All solutions were diluted to an absorbance of 0.1 or less (at the corresponding excitation wavelength) to minimize reabsorption by the fluorophores.

[0072] like Figure 5 As shown, the sample 1 prepared in Example 1 of the present invention, Cu 2-x Se@SiO2 nanocrystals and CuInSe x S 2-x UV-visible-near-infrared absorption spectrum of ZnS, where the horizontal axis is wavelength and the vertical axis is absorption intensity. Figure 5 It can be seen that Cu 2- x Se@SiO2 shows a near-infrared absorption band caused by plasmon resonance, with an absorption peak at 1192nm (1.04eV). x S 2-x / ZnS quantum dots have a very thin ZnS shell, so the absorption spectrum is less affected by the ZnS shell. Sample 1 has a wide range of light absorption response in the range of 300 to 1000 nm. 2-x The amount of Se@SiO2 nanoparticles added is small, and its response to light absorption mainly comes from CuInSe x S 2-x / ZnS quantum dots, but the Cu 2-x The LSPR absorption peak of Se@SiO2 nanoparticles indicates that compounding quantum dots with them will enhance the light absorption ability of quantum dots in the near-infrared region, which can promote the utilization of light to a certain extent and thus enhance the optical properties of quantum dots.

[0073] like Figure 6 As shown in the figure, the fluorescence enhancement factor curve comparison of the materials prepared in Example 1, Example 2 and Example 3 of the present invention, wherein the horizontal axis is Cu 2-x Se@SiO2 nanoparticle content, the vertical axis is the fluorescence enhancement factor. Figure 6 It can be seen that the sample 1 prepared in Example 1 shows better near-infrared fluorescence emission than the sample 2 prepared in Example 2 and the sample 3 prepared in Example 3, indicating that Cu 2-x Se@SiO2 nanoparticles and CuInSe x S 2-x The volume ratio of Cu / ZnS quantum dots plays a crucial role in the luminescence properties of quantum dots. 2-x When there are too few Se@SiO2 nanoparticles, it is not enough to provide sufficient electric field strength for quantum dots (when Cu 2-x Se@SiO2 chloroform solution and CuInSe x S 2-x When the volume ratio of Cu / ZnS chloroform solution is 1:200, the fluorescence intensity of the prepared nanocomposite material is 0.19 times that of Example 1, and its fluorescence quantum yield is also reduced to 5.4%). 2-x When there are more Se@SiO2 nanoparticles, the presence of the localized surface plasmon resonance effect leads to the dominance of direct energy transfer, which competes with the intrinsic fluorescence emission of quantum dots, greatly improving the energy transfer efficiency from quantum dots to nanoparticles and suppressing the radiation recombination rate of quantum dots, which leads to fluorescence quenching. 2- x When the Se@SiO2 nanoparticles content is appropriate, that is, the volume ratio is 1:16, the strongest fluorescence emission is exhibited.

[0074] like Figure 7As shown in FIG. 1 , the near-infrared fluorescence spectra of the materials obtained in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention are compared, wherein the horizontal axis is the wavelength and the vertical axis is the fluorescence intensity. Figure 7 As can be seen, compared with the sample 1 prepared in Example 1 and the comparative sample 1 prepared in Comparative Example 1, the fluorescence of the comparative sample 2 prepared in Comparative Example 2 was quenched, indicating that when CuInSe x S 2-x / ZnS quantum dots directly interact with Cu 2-x When Se nanocrystals are composited, due to the 2-x The strong LSPR effect of Se nanocrystals promotes the transfer of quantum dots to Cu 2-x The direct energy transfer of Se leads to the quenching of quantum dot fluorescence. However, when the quantum dots are combined with Cu2O3 and SiO2 with a thickness of 10.5 nm in Example 1, the fluorescence of the quantum dots is quenched. 2-x When Se@SiO2 is coupled, the fluorescence intensity is improved most efficiently, which is almost three times that of comparative example 1. x S 2-x / ZnS quantum dots and Cu 2-x The dielectric layer between Se can effectively adjust the distance between the two and effectively promote the 2-x Se@SiO2 and CuInSe x S 2-x / ZnS quantum dots, accompanied by the resonant energy transfer between Cu 2-x Part of the hot electrons in Se@SiO2 are transferred to CuInSe x S 2-x / ZnS quantum dots and further improve their radiative recombination rate, thereby enhancing the fluorescence of the quantum dots.

[0075] like Figure 8 As shown in the figure, the fluorescence lifetime comparison diagram of the materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention is shown, wherein the horizontal axis is time and the vertical axis is intensity. The insert table in the figure shows the average fluorescence lifetime and photoinduced quantum yield of the three materials. Figure 8 It can be seen that the fluorescence lifetimes of sample 1 prepared in Example 1, comparative example 1 and comparative example 2 are 11.0 μs, 8.0 μs and 5.5 μs respectively. The quantum yield of sample 1 prepared in Example 1 is as high as 45%, which is higher than that of the sample without adding Cu. 2-x Se@SiO2 nanocrystals are 6.37 times that of comparative example 1, which is directly coupled to Cu 2-x Se nanocrystals are 11.25 times that of comparative example 2. 2-x Se@SiO2-CuInSe x S 2-x / ZnS nanocomposites have excellent optical properties, which is due to the 2-xSe nanocrystals and CuInSe x S 2-x The ZnS quantum dots are reasonably isolated by silicon dioxide, and effective resonance energy transfer occurs between the two, which stimulates more electron transitions in the quantum dots to a certain extent and is accompanied by the Cu 2-x The transfer of hot electrons in Se nanocrystals promotes the radiative recombination of quantum dots, thereby improving the fluorescence lifetime and quantum yield of quantum dots.

[0076] Experimental Example 2 Performance Test

[0077] The properties of the materials prepared in Example 1 and Comparative Example 1 (as fluorescent groups) were tested as follows:

[0078] Preparation of the Luminescent Solar Concentrator: Sample 1 (prepared in Example 1) or Comparative Sample 1 (prepared in Comparative Example 1) dispersed in chloroform was added to a 50 mL beaker. The solvent was removed by vacuum filtration, and nitrogen was then introduced to prevent oxidation of Sample 1 or Comparative Sample 1. Subsequently, dodecyl methacrylate and ethylene glycol dimethacrylate monomers were mixed in a 4:1 mass ratio. The resulting solution was mixed with a UV initiator (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide) and sonicated until a clear solution was obtained. This solution was then poured into a flask containing the dried powder of Sample 1 or Comparative Sample 1. The mixture was evenly dispersed by sonication and then injected into a mold consisting of two glass sheets and a spacer, with a thickness of approximately 3 mm between the glass sheets. The mold was cured by UV irradiation (wavelength 385 nm) for 5 minutes, and finally annealed at 70°C for 5 minutes and cooled to room temperature for demolding.

[0079] Performance test of luminescent solar concentrator: A commercial solar monocrystalline silicon cell was fixed to the edge of the luminescent solar concentrator with black tape. The cell area was 1cm×10cm. Its width was larger than the thickness of the LSC (0.3cm), so the black tape was used to cover the free area of ​​the monocrystalline silicon cell and the remaining side of the LSC. A black matte plate was placed at the bottom of the test platform to prevent the light that passed through the LSC from being reflected back and overestimating the performance of the LSC. The light source was a simulated AM 1.5G spectrum (100mW / cm 2 ), calibrated by a calibration simulator using a calibration solar cell.

[0080] like Figure 9 As shown in the figure, the current density-voltage (JV) curves of the materials prepared in Example 1 and Comparative Example 1 of the present invention are applied to luminescent solar concentrators of different areas, wherein the horizontal axis is the open circuit voltage and the vertical axis is the short circuit current density; (a) is the current density-voltage (JV) curve of Example 1 and Comparative Example 1 based on 2×2×0.3 cm 3The photoelectric conversion efficiency (PCE) of the luminescent solar concentrator (LSCs) with respect to the area is shown in FIG1 ; (b) is the PCE of Example 1 and Comparative Example 1 based on 4×4×0.3 cm 3 The photoelectric conversion efficiency (PCE) of the luminescent solar concentrator (LSCs) with respect to the area is shown in FIG1 ; (c) is the PCE of Example 1 and Comparative Example 1 based on a 6×6×0.3 cm 3 The photovoltaic conversion efficiency (PCE) of luminescent solar concentrators (LSCs) with respect to the area. Figure 9 As can be seen from (a) to (c), Example 1 and Comparative Example 1 are based on 2×2×0.3 cm 3 , 4×4×0.3cm 3 and 6×6×0.3cm 3 The photoelectric conversion efficiency (PCE) of the luminescent solar concentrators (LSCs) of different areas shows that Example 1 is higher than that of Comparative Example 1, indicating that compared with the Cu-free 2- x The comparative example 1 and the embodiment 1 with Se@SiO2 nanocrystals added have more excellent photoelectric performance. Figure 9 Compared with (b) and (c), Figure 9 (a) has the best performance (because the larger the light receiving area of ​​the luminescent solar concentrator, the more likely the fluorescent groups inside it will be reabsorbed or aggregated, which will lead to quantum dot quenching and reduce its photoelectric conversion efficiency). Figure 9 2×2×0.3cm prepared in Comparative Example 1 in (a) 3 The PCE of small-area LSC is only 0.29%, while the PCE of sample 1 in Example 1 is only 0.29% in small-area LSC (2×2×0.3 cm 3 The highest short-circuit current density of the LSC is 3.37 mA cm -2 , the open circuit voltage is 0.39 V, and the PCE can reach up to 0.42%, which is increased by about 41%. 2-x The addition of Se@SiO2 nanocrystals can provide a local electromagnetic field, and resonant energy transfer occurs through the local field strength effect, which enables the quantum dots to excite more additional electrons for radiative recombination and inhibits the occurrence of non-radiative recombination, resulting in enhanced fluorescence of the quantum dots and greatly improved fluorescence quantum yield. At the same time, it can make up for the defect of weak light absorption of quantum dots in the near-infrared band of 1100-1400nm, promote the photon utilization rate of quantum dots, and thus obtain higher photoelectric conversion efficiency.

[0081] Light stability test of luminescent solar concentrator: The luminescent solar concentrator was placed under UV light (385nm) for 2 hours continuously, with the incident power on the sample surface being 35mW / cm 2The optical densities of the LSC prepared based on Comparative Example 1 and the LSC prepared based on Example 1 at the excitation wavelength are 0.36 and 0.38, respectively.

[0082] like Figure 10 As shown in FIG. 1 , the light stability comparison diagram of the materials prepared in Example 1 of the present invention and Comparative Example 1 when used in a luminescent solar concentrator is shown, wherein the horizontal axis is the ultraviolet irradiation time and the vertical axis is the fluorescence intensity ratio. Figure 10 It can be seen that after 30 minutes of UV irradiation, the fluorescence intensity of the LSC prepared in Example 1 decreased by about 22%, while the fluorescence of the LSC prepared in Comparative Example 1 was quenched. When the illumination time was extended to 2 hours, the LSC prepared in Example 1 still maintained about 53% of the concentrated light intensity, and its photostability was much higher than that of the LSC prepared in Comparative Example 1.

[0083] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a nanocomposite material of near-infrared localized surface plasmon resonance nanocrystals and quantum dots, characterized in that: The method includes: In the dark, Cu 2-x Se@SiO2 nanocrystals in chloroform solution and CuInSe x S 2-x / ZnS chloroform solution was mixed and stirred, and collected to obtain the nanocomposite material; The Cu 2-x Se@SiO2 nanocrystal chloroform solution and the CuInSe x S 2-x The volume ratio of ZnS / chloroform solution is 1:(10-200); The Cu 2-x The absorbance of Se@SiO2 nanocrystal chloroform solution at the localized surface plasmon resonance absorption band is 0.18; The CuInSe x S 2-x The concentration of ZnS in chloroform solution was 0.46 mg / mL.

2. The preparation method according to claim 1, characterized in that The CuInSe x S 2-x / ZnS chloroform solution was prepared by the following method: (1) dissolving cuprous iodide and indium acetate in a mixture of dodecanethiol and oleylamine, degassing under vacuum at 90°C, raising the temperature to 140°C under nitrogen protection and stirring to fully dissolve, heating the temperature to 180-230°C (not equal to 230°C), injecting dodecanethiol-oleylamine-selenium solution, then heating to 230°C for reaction, and then injecting ZnS precursor for reaction; (2) After the reaction is completed, cool to 60-80°C, centrifuge and purify with chloroform and acetone, and disperse in chloroform to obtain CuInSe x S 2-x / ZnS chloroform solution.

3. The preparation method according to claim 2, characterized in that The dodecanethiol-oleylamine-selenium solution is prepared by mixing selenium powder, oleylamine and dodecanethiol under nitrogen atmosphere at room temperature; the ZnS precursor is prepared by dissolving zinc stearate in a mixture of octadecene, oleic acid and dodecanethiol, degassing under vacuum at 80°C, and heating at 150°C.

4. The preparation method according to claim 1, characterized in that The Cu 2-x Se@SiO2 nanocrystal chloroform solution was prepared by the following method: (1) Disperse the surfactant in cyclohexane, add ethyl orthosilicate, ammonia solution and Cu 2-x Se chloroform solution was stirred continuously in the dark; after the reaction was completed, ethanol was added and centrifuged to separate Cu 2-x Se@SiO2 nanocrystals, Cu 2-x Se@SiO2 nanocrystals were dispersed in anhydrous ethanol and aged to obtain Cu 2-x Se@SiO2 ethanol solution; (2) Cu 2-x Se@SiO2 nanocrystal ethanol solution was mixed with ammonia water to adjust the pH value to alkaline, and octadecyltrimethoxysilane chloroform solution was added under continuous stirring at a speed of 800-1000 rpm / min. The reaction was continued under stirring at a speed of 800-1000 rpm / min, and then the mixture was centrifuged, purified, washed, and dispersed in chloroform to obtain the Cu@SiO2 nanocrystal. 2-x Se@SiO2 nanocrystals in chloroform solution.

5. The preparation method according to claim 4, characterized in that The surfactant is polyoxyethylene nonylphenyl ether; the Cu 2-x The absorbance of Se@SiO2 ethanol solution in the localized surface plasmon resonance absorption band is 0.

21.

6. The preparation method according to claim 4, characterized in that The Cu 2-x Se chloroform solution is prepared by mixing cuprous chloride powder with oleylamine, degassing at 110°C, heating to 225°C, injecting oleic acid-selenium precursor when the solution turns into a transparent dark yellow, lowering the temperature to 205°C and maintaining it at 205°C, then cooling to 60°C, adding ethanol, centrifuging and purifying, and dispersing it in chloroform to obtain Cu 2-x Se chloroform solution; The Cu 2-x CuSe in chloroform solution 2-x The concentration of Se was 1.6 mg / mL.

7. The preparation method according to claim 6, characterized in that The oleic acid-selenium precursor is prepared by dissolving selenium powder in oleic acid, evacuating the mixture at 90°C, heating the mixture to 220°C and then to 280°C under nitrogen atmosphere until the solution becomes a yellow transparent clear liquid.

8. A nanocomposite material obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the nanocomposite material according to claim 8 in the field of luminescent solar concentrators.

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