Chiral copper sulfide nanomaterial, and preparation method and application thereof

Abstract

The application belongs to the technical field of nanometer materials, and discloses a chiral copper sulfide nanometer material and a preparation method and application thereof. The chiral copper sulfide nanometer material takes arginine or histidine as a chiral ligand, has a circular dichroism spectral response peak in an ultraviolet band, a visible light band and a near-infrared band, and presents a significant chiral plasmonic signal in the visible-near-infrared region. The chiral ligand is not only modified on the surface of the copper sulfide nanometer material, but also induces chiral distortion of a copper sulfide surface lattice. Chiral information of the ligand is effectively transmitted to the entire inorganic framework, and a nanometer assembly with a chiral geometric structure is formed. The chiral copper sulfide nanometer material solves the problem that a chiral CuS nanostructure constructed by using an existing chiral ligand has a narrow spectral response range and cannot respond to visible light and a near-infrared band.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, and relates to a chiral copper sulfide nanomaterial, its preparation method and application. Background Technology

[0002] Copper sulfide (CuS) is a transition metal sulfide that exists in nature as covellite, a dark brown amorphous powder or granular solid with a metallic luster. As an important p-type semiconductor material, copper sulfide possesses a unique layered crystal structure, excellent photoelectric properties and chemical stability, as well as good optical absorption and a significant near-infrared localized surface plasmon resonance (LSPR) effect, making it promising for applications in photothermal therapy, catalytic reactions, and optoelectronic devices. However, this LSPR absorption itself is not chiral, requiring special structural design to extend its chiral optical activity to the visible-near-infrared band. Traditionally prepared CuS nanomaterials often exhibit symmetrical structures such as spherical or sheet-like shapes, lacking tunable chiral characteristics and making it difficult to effectively control circularly polarized light and chiral electromagnetic responses. Therefore, developing a method for controllably constructing chiral CuS nanostructures is of great significance for expanding the application of this material in chiral optoelectronics and functional materials.

[0003] Existing methods for constructing chiral CuS nanostructures using chiral ligands often employ chiral amino acids such as cysteine ​​and penicillamine as ligands. During the synthesis of copper sulfide nanoparticles, chiral structures are induced through ligand-metal coordination. However, existing ligands have narrow spectral response ranges, exhibiting chiral optical activity only in the ultraviolet region (<400 nm). This makes it difficult to redshift to the visible and near-infrared bands using such ligand-induced strategies, failing to meet the practical application requirements of deep tissue penetration and low photodamage in fields such as bioimaging and phototherapy. This restricts the practical application of chiral copper sulfide nanomaterials in bioimaging and chiral optoelectronic devices. Therefore, there is an urgent need to develop a chiral copper sulfide nanomaterial capable of imaging in the visible light range. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a chiral copper sulfide nanomaterial, its preparation method, and its applications. This chiral copper sulfide nanomaterial uses arginine or histidine as chiral ligands, exhibiting circular dichroism spectral response peaks in the ultraviolet, visible, and near-infrared bands, and displaying significant chiral plasmon signals in the visible-near-infrared region. This indicates that the chiral ligands not only modify the surface of the copper sulfide nanomaterial but also induce chiral distortion of the copper sulfide surface lattice. The chiral information of the ligands is effectively transferred to the entire inorganic framework, forming a nano-assembly with a chiral geometry. The chiral copper sulfide nanomaterial of this invention solves the problem of narrow spectral response range and inability to respond to visible and near-infrared bands in existing chiral ligand-induced chiral CuS nanostructures. This material can be widely used in visible circular polarization detection, near-infrared polarization imaging detection, and broadband circular polarization state identification detection.

[0005] On one hand, the present invention provides a chiral copper sulfide nanomaterial, wherein the chiral copper sulfide nanomaterial is a chiral ligand-modified copper sulfide nanomaterial;

[0006] The chiral ligand is arginine or histidine; The chiral copper sulfide nanomaterial exhibits circular dichroism spectral response in the ultraviolet, visible, and near-infrared bands, and chiral plasmon response in the visible and near-infrared bands.

[0007] Furthermore, the arginine is L-arginine or D-arginine; The histidine is L-histidine or D-histidine; The wavelength range of the ultraviolet band is 180~350 nm; The wavelength range of the visible and near-infrared bands is 400~1000 nm.

[0008] Specifically, the circular dichroism (CD) spectra of chiral copper sulfide nanomaterials detected by this invention revealed that in the ultraviolet range (180–350 nm), the peaks of L-Arg-CuS and D-Arg-CuS appeared at 200 nm and ~250 nm, while L-His-CuS@S and D-His-CuS@S exhibited high-intensity, sharp mirror peaks at 195 nm and 213 nm. Furthermore, regardless of whether histidine or arginine was used, the CD spectra of both L-type and D-type samples were symmetric about the zero axis. In the visible and near-infrared bands (400–1000 nm), the CD spectra of L-Arg-CuS and D-Arg-CuS showed broadened chiral response peaks in the 550–700 nm range, and distinct positive and negative mirror peaks at 590 nm and 753 nm. L-His-CuS@S and D-His-CuS@S exhibited a combination of one large and two small symmetrical peaks at 435 nm, 570 nm, and 693 nm. In contrast, chiral copper sulfide nanomaterials modified with cysteine, proline, tartaric acid, or glutamic acid only showed positive and negative mirror peaks in the ultraviolet band, but no obvious chiral signals were detected in the visible and near-infrared bands.

[0009] Specifically, the present invention detected the ultraviolet-visible absorption spectrum of chiral copper sulfide nanomaterials and found that the chiral copper sulfide nanomaterials modified with arginine and histidine as chiral ligands exhibited plasmon resonance absorption in the visible and near-infrared bands. This indicates that the chiral ligands not only modify the surface of the copper sulfide nanomaterials, but also induce chiral distortion of the copper sulfide surface lattice. The chiral information of the ligands is effectively transferred to the entire inorganic framework, forming a nano-assembly with a chiral geometric structure.

[0010] On the other hand, this invention claims protection for a method for preparing the above-mentioned chiral copper sulfide nanomaterials, comprising: S1: To prepare a copper sulfide colloidal solution, weigh 85–340 mg (0.5–2 mmol) of CuCl₂·2H₂O and dissolve it in 60 mL of ultrapure water. Add the solution to a 200 mL beaker, add 4.0 g of PVP-K30, and stir magnetically until the solid is completely dissolved. Stir at 1500 rpm and slowly add 1–10 mL of a 17 wt% (NH₄)₂S solution. After the addition, the solution turns dark brown (primary CuS crystal nuclei begin to form). Continue stirring magnetically for 30 min to obtain the copper sulfide colloidal solution.

[0011] S2: Preparation of copper sulfide nanosheets. The S1 colloidal solution was completely transferred to a PTFE-lined stainless steel high-pressure reactor. The reactor was placed stably in a forced-air drying oven, and the reaction temperature was set to 180℃. The reaction was carried out at this constant temperature for 12 h. After the reaction, the reactor was allowed to cool naturally to room temperature. The reaction product was transferred to a 50 mL centrifuge tube and centrifuged at 6000-12000 rpm for 15 min. The supernatant was discarded. Deionized water was added to the precipitate for redispersion, followed by centrifugation and washing. This washing step was repeated three times to thoroughly remove free ligands and inorganic byproducts. The collected black precipitate was frozen and then dried in a vacuum freeze dryer for 20 h to obtain a dried solid powder sample, i.e., copper sulfide nanosheets.

[0012] S3: Preparation of chiral copper sulfide nanoflowers: Copper sulfide nanosheets were dissolved in 20 mL of ultrapure water and placed in a magnetic stirrer at 800 rpm. 10 mL of chiral ligand solution was slowly added, and the mixture was stirred for 24 h. The reaction product was transferred to a 50 mL centrifuge tube and centrifuged at 6000–12000 rpm for 15 min. The supernatant was discarded. Deionized water was added to the precipitate for redispersion, followed by centrifugation and washing. This washing step was repeated three times to thoroughly remove free ligands and inorganic byproducts. The collected black precipitate was frozen and dried in a vacuum freeze dryer for 20 h to obtain a dried solid powder sample, i.e., chiral copper sulfide nanoflowers.

[0013] Furthermore, the concentration of the chiral amino acid ligand in the chiral ligand solution is 0.1~0.5 M; Furthermore, the volume ratio of the chiral ligand solution to the mass ratio of the copper sulfide nanosheets is 1:0.5~2.

[0014] On the other hand, the present invention seeks protection for the application of the above-mentioned chiral copper sulfide nanomaterials in circularly polarized light detection.

[0015] Furthermore, this invention seeks protection for the application of the aforementioned chiral copper sulfide nanomaterials in chiral photoelectric detection.

[0016] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages: (1) This invention provides a chiral copper sulfide nanomaterial using arginine or histidine as chiral ligands. This chiral copper sulfide nanomaterial exhibits circular dichroism spectral response peaks in the ultraviolet, visible, and near-infrared bands, and displays significant chiral plasmon signals and mirror-symmetric Cotton effects in the visible-near-infrared region. This indicates that the chiral ligands not only modify the surface of the copper sulfide nanomaterial but also induce chiral distortion of the copper sulfide surface lattice. The chiral information of the ligands is effectively transferred to the entire inorganic framework, forming a nano-assembly with a chiral geometric structure. In contrast, chiral copper sulfide nanomaterials modified with cysteine, proline, tartaric acid, or glutamic acid mainly exhibit that the surface modification effect is difficult to induce significant chiral plasmon responses. The chiral copper sulfide nanomaterial of this invention solves the problem that the existing chiral CuS nanostructures induced by chiral ligands have a narrow spectral response range and cannot respond to the visible and near-infrared bands. Visible and near-infrared light have the advantages of strong penetration, low self-absorption interference from biological matrices, and readily available light source equipment. Therefore, the chiral copper sulfide material of this invention can not only realize visible circularly polarized light detection, but also be extended to detection scenarios such as near-infrared polarization imaging, in-situ sensing of biological chiral molecules, and chiral optical imaging of living tissue, greatly broadening the application scope of chiral copper sulfide in the field of polarized light detection.

[0017] (2) The circular dichroism (CD) spectra of chiral copper sulfide nanomaterials detected by this invention revealed that, in the ultraviolet band (180~350 nm), the peaks of L-Arg-CuS and D-Arg-CuS appeared at 200 nm and ~250 nm, while L-His-CuS@S and D-His-CuS@S exhibited high-intensity, sharp positive and negative mirror peaks at 195 nm and 213 nm. Furthermore, regardless of whether histidine or arginine was used, the CD spectra of both L-type and D-type samples were symmetric about the zero axis. In the visible and near-infrared bands (400–1000 nm), the CD spectra of L-Arg-CuS and D-Arg-CuS showed broadened chiral response peaks in the 550–700 nm range, and distinct positive and negative mirror peaks at 590 nm and 753 nm. L-His-CuS@S and D-His-CuS@S exhibited a combination of one large and two small symmetrical peaks at 435 nm, 570 nm, and 693 nm. In contrast, chiral copper sulfide nanomaterials modified with cysteine, proline, tartaric acid, or glutamic acid only showed positive and negative mirror peaks in the ultraviolet band, but no obvious chiral signals were detected in the visible and near-infrared bands.

[0018] (3) The main diffraction peak positions and intensity distributions of the chiral copper sulfide nanomaterials of this invention are basically consistent with those of the standard card for hexagonal copper sulfide, indicating that the sample maintains the hexagonal CuS crystal structure and the chiral ligand modification does not destroy the CuS framework structure. Among them, arginine can selectively remove elemental sulfur through nucleophilic attack of guanidinium and amino groups, converting insoluble elemental sulfur into soluble polysulfides or thiolated organic compounds, thereby selectively etching away the sulfur component from the heterostructure interface and exposing the pure hexagonal CuS phase. The synergistic coordination of carboxyl and guanidinium groups in arginine can further stabilize the CuS surface and prevent lattice collapse. The modification effects of other amino acids are either to destroy the original hexagonal CuS phase or to encapsulate and isolate it, resulting in the attenuation of the copper sulfide signal. Among them, the -SH functional group in cysteine ​​has a significant effect on CuS. 2+ It has a strong affinity and forms Cu-S interaction. At the same time, cysteine ​​molecules can cross-assemble through hydrogen bonds and disulfide bonds to encapsulate or isolate the small amount of CuS particles generated, resulting in severe attenuation or even annihilation of their diffraction signal. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 Circular dichroism spectra of Arg-modified and His-modified chiral copper sulfide nanoflowers. Figure 1 In this context, 'a' represents Arg-modified chiral copper sulfide nanoflowers at 180–350 nm. Figure 1 b in the figure represents His-modified chiral copper sulfide nanoflowers at 180~350 nm. Figure 1 c in the text refers to Arg-modified chiral copper sulfide nanoflowers at a wavelength of 350–1000 nm. Figure 1 In this context, d represents His-modified chiral copper sulfide nanoflowers at a wavelength of 350–1000 nm.

[0021] Figure 2 The circular dichroism spectra of chiral copper sulfide nanoflowers modified with Cys, Pro, Tra, and Glu are shown in the range of 180–350 nm. Figure 2 In this context, 'a' represents Cys-modified chiral copper sulfide nanoflowers. Figure 2 In this context, b represents Pro-modified chiral copper sulfide nanoflowers; Figure 2 In this context, c represents Tra-modified chiral copper sulfide nanoflowers; Figure 2 In this context, d represents Glu-modified chiral copper sulfide nanoflowers.

[0022] Figure 3 The absorption asymmetry factor spectra of Arg-modified and His-modified chiral copper sulfide nanoflowers are shown. Figure 3 In this context, 'a' represents Arg-modified chiral copper sulfide nanoflowers at 180–350 nm. Figure 3 b in the text refers to Arg-modified chiral copper sulfide nanoflowers at a wavelength of 350–1000 nm. Figure 3 c in the text refers to His-modified chiral copper sulfide nanoflowers at 180~350 nm. Figure 3 In this context, d represents His-modified chiral copper sulfide nanoflowers at a wavelength of 350–1000 nm.

[0023] Figure 4 The absorption asymmetry factor spectra of Cys, Pro, Tra and Glu-modified chiral copper sulfide nanoflowers are shown in the range of 180–350 nm. Figure 4 In this context, 'a' represents Cys-modified chiral copper sulfide nanoflowers. Figure 4 In this context, b represents Pro-modified chiral copper sulfide nanoflowers; Figure 4 In this context, c represents Tra-modified chiral copper sulfide nanoflowers; Figure 4 In this context, d represents Glu-modified chiral copper sulfide nanoflowers.

[0024] Figure 5 The UV-Vis absorption spectra of Arg-modified and His-modified chiral copper sulfide nanoflowers. Figure 5 In this context, 'a' represents Arg-modified chiral copper sulfide nanoflowers at 180–350 nm. Figure 5 b in the text refers to Arg-modified chiral copper sulfide nanoflowers at a wavelength of 350–1000 nm. Figure 5 c in the text refers to His-modified chiral copper sulfide nanoflowers at 180~350 nm. Figure 5 In this context, d represents His-modified chiral copper sulfide nanoflowers at a wavelength of 350–1000 nm.

[0025] Figure 6 The UV-Vis absorption spectra of chiral copper sulfide nanoflowers modified with Cys, Pro, Tra, and Glu are shown in the range of 180–350 nm. Figure 6 In this context, 'a' represents Cys-modified chiral copper sulfide nanoflowers. Figure 6 In this context, b represents Pro-modified chiral copper sulfide nanoflowers; Figure 6 In this context, c represents Tra-modified chiral copper sulfide nanoflowers; Figure 6 In this context, d represents Glu-modified chiral copper sulfide nanoflowers.

[0026] Figure 7 X-ray diffraction patterns of chiral copper sulfide nanoflowers modified with different ligands. Figure 7 In this diagram, 'a' represents the X-ray diffraction pattern. Figure 7In the figure, b represents the relative intensity ratio of the diffraction peak of the 222 crystal plane of S to the diffraction peak of the 110 crystal plane of CuS.

[0027] Figure 8 C1s high-resolution XPS spectra of chiral copper sulfide nanoflowers modified with different amino acids. Figure 8 In the figure, 'a' represents the control copper sulfide nanoflowers; Figure 8 In this context, b represents Cys-modified chiral copper sulfide nanoflowers; Figure 8 In this context, c represents Tra-modified chiral copper sulfide nanoflowers; Figure 8 In this context, d represents Glu-modified chiral copper sulfide nanoflowers; Figure 8 In this context, 'e' represents His-modified chiral copper sulfide nanoflowers. Figure 8 f in the figure represents Arg-modified chiral copper sulfide nanoflowers.

[0028] Figure 9 XPS spectra of Cu 2p in chiral copper sulfide nanoflowers modified with different ligands. Figure 9 In the figure, 'a' represents the control copper sulfide nanoflowers; Figure 9 In this context, b represents Cys-modified chiral copper sulfide nanoflowers; Figure 9 In this context, c represents Tra-modified chiral copper sulfide nanoflowers; Figure 9 In this context, d represents Glu-modified chiral copper sulfide nanoflowers; Figure 9 In this context, 'e' represents His-modified chiral copper sulfide nanoflowers. Figure 9 f in the figure represents Arg-modified chiral copper sulfide nanoflowers.

[0029] Figure 10 Cu in chiral copper sulfide nanoflowers modified with different ligands + 2p 3 / 2 and Cu 2+ 2p 3 / 2 The binding energy spectrum.

[0030] Figure 11 XPS spectra of the S 2p region of chiral copper sulfide nanoflowers modified with different ligands. Figure 11 In the figure, 'a' represents the control copper sulfide nanoflowers; Figure 11 In this context, b represents Cys-modified chiral copper sulfide nanoflowers; Figure 11 In this context, c represents Tra-modified chiral copper sulfide nanoflowers; Figure 11 In this context, d represents Glu-modified chiral copper sulfide nanoflowers; Figure 11 In this context, 'e' represents His-modified chiral copper sulfide nanoflowers. Figure 11 f in the figure represents Arg-modified chiral copper sulfide nanoflowers.

[0031] Figure 12 S-Cu and S-Fe2O3 in chiral copper sulfide nanoflowers modified with different ligands 2-S2 2- The binding energy and proportion of SO. Figure 12 In this diagram, 'a' represents the binding energy spectrum. Figure 12 In this context, b represents the proportion of different S components.

[0032] Figure 13 A graph showing the elemental proportions of Cu, S, C, O, and N in chiral copper sulfide nanoflowers modified with different ligands.

[0033] Figure 14 This is a diagram showing the geometric structure and charge distribution of different ligand molecules. Detailed Implementation

[0034] The technical solution of the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods and detection methods described in each embodiment are conventional methods; unless otherwise specified, the reagents and materials can be purchased commercially. Unless otherwise specified, the percentages in the following embodiments refer to mass percentages.

[0035] The manufacturers of L-arginine (L-Arg), D-arginine (D-Arg), L-histidine (L-His), D-histidine (D-His), L-cysteine ​​(L-Cys), and D-cysteine ​​(D-Cys) are all Shanghai Aladdin Biochemical Technology Co., Ltd. The purity of L-arginine, D-arginine, and D-cysteine ​​is 98%, the purity of L-cysteine ​​is 99%, and the purity of L-histidine and D-histidine is ≥99%.

[0036] Both L-proline (L-Pro) and D-proline (D-Pro) are manufactured by Tokyo Chemical Industry Co., Ltd. (TCI), and their purity is ≥99%.

[0037] Both L-tartaric acid (L-Tra) and D-tartaric acid (D-Tra) are manufactured by Shanghai Maclean Biochemical Technology Co., Ltd. The purity of L-tartaric acid is ≥99.5%, and the purity of D-tartaric acid is 99%.

[0038] The chiral copper sulfide nanomaterials prepared in the following examples exhibit a flower-like morphology, and are therefore sometimes simply referred to as nanoflowers (NFs).

[0039] Example 1 This embodiment provides a method for preparing chiral copper sulfide nanoflowers, specifically including the following steps: S1: To prepare a copper sulfide colloidal solution, weigh 170 mg (1 mmol) of CuCl2·2H2O and dissolve it in 60 mL of ultrapure water. Add the solution to a 200 mL beaker, and add 4.0 g of PVP-K30. Stir magnetically until the solid is completely dissolved (the solution turns light blue). Stir at 1500 rpm and slowly add 5 mL of a 17 wt% (NH4)2S solution. After the addition, the solution turns dark brown (primary CuS crystal nuclei begin to form). Continue stirring magnetically for 30 min to obtain the copper sulfide colloidal solution.

[0040] S2: Preparation of copper sulfide nanosheets. The entire S1 colloidal solution was transferred to a 100 mL PTFE-lined stainless steel high-pressure reactor. The reactor was placed stably in a forced-air drying oven, and the reaction temperature was set to 180℃. The reaction was carried out at this constant temperature for 12 h. After the reaction, the reactor was allowed to cool naturally to room temperature. The reaction product was transferred to a 50 mL centrifuge tube and centrifuged at 8000 rpm for 15 min. The supernatant was discarded. Deionized water was added to the precipitate for redispersion, followed by centrifugation and washing. This washing step was repeated three times to thoroughly remove free ligands and inorganic byproducts. The final collected black precipitate was frozen and then dried in a vacuum freeze dryer for 20 h to obtain a dried solid powder sample, i.e., copper sulfide nanosheets.

[0041] S3: Preparation of chiral copper sulfide nanoflowers: 10 mg of copper sulfide nanosheets were dissolved in 20 mL of ultrapure water and placed in a magnetic stirrer at 800 rpm. 10 mL of 0.3 M chiral ligand L-Arg was slowly added, and the mixture was stirred for 24 h. The reaction product was transferred to a 50 mL centrifuge tube and centrifuged at 8000 rpm for 15 min. The supernatant was discarded. Deionized water was added to the precipitate for redispersion, followed by centrifugation and washing. This washing step was repeated three times to thoroughly remove free ligands and inorganic byproducts. The collected black precipitate was frozen and dried in a vacuum freeze dryer for 20 h to obtain a dried solid powder sample, i.e., chiral copper sulfide nanoflowers.

[0042] Following the above preparation method, by changing the type of chiral ligand, D-Arg, L- / D-His, L- / D-Cys, L- / D-Pro, L- / D-Tra, and L- / D-Glu were used as ligands to prepare corresponding L / D ligand-modified CuS nanoflower samples. A control group was also prepared by adding only PVP-K30 without chiral amino acids. After the S2 reaction was completed, the samples were allowed to stand to obtain PVP-CuS achiral nanostructures (PVP NFs).

[0043] Example 2 This embodiment provides a method for preparing chiral copper sulfide nanoflowers, specifically including the following steps: S1: To prepare a copper sulfide colloidal solution, weigh 85 mg (0.5 mmol) CuCl2·2H2O and dissolve it in 60 mL of ultrapure water. Add the solution to a 200 mL beaker, and add 4.0 g of PVP-K30. Stir magnetically until the solid is completely dissolved (the solution turns light blue). Stir at 1500 rpm and slowly add 1 mL of a 17 wt% (NH4)2S solution. After the addition, the solution turns dark brown (primary CuS crystal nuclei begin to form). Continue stirring magnetically for 30 min to obtain the copper sulfide colloidal solution.

[0044] S2: Preparation of copper sulfide nanosheets. The entire S1 colloidal solution was transferred to a 100 mL PTFE-lined stainless steel high-pressure reactor. The reactor was placed stably in a forced-air drying oven, and the reaction temperature was set to 180℃. The reaction was carried out at this temperature for 12 h. After the reaction, the reactor was allowed to cool naturally to room temperature. The reaction product was transferred to a 50 mL centrifuge tube and centrifuged at 6000 rpm for 15 min. The supernatant was discarded. Deionized water was added to the precipitate for redispersion, followed by centrifugation and washing. This washing step was repeated three times to thoroughly remove free ligands and inorganic byproducts. The final collected black precipitate was frozen and then dried in a vacuum freeze dryer for 20 h to obtain a dried solid powder sample, i.e., copper sulfide nanosheets.

[0045] S3: Preparation of chiral copper sulfide nanoflowers: 5 mg of copper sulfide nanosheets were dissolved in 20 mL of ultrapure water and placed in a magnetic stirrer at 800 rpm. 10 mL of 0.1 M chiral ligand L-Arg was slowly added, and the mixture was stirred for 24 h. The reaction product was transferred to a 50 mL centrifuge tube and centrifuged at 6000 rpm for 15 min. The supernatant was discarded. Deionized water was added to the precipitate for redispersion, followed by centrifugation and washing. This washing step was repeated three times to thoroughly remove free ligands and inorganic byproducts. The collected black precipitate was frozen and dried in a vacuum freeze dryer for 20 h to obtain a dried solid powder sample, i.e., chiral copper sulfide nanoflowers.

[0046] Example 3 This embodiment provides a method for preparing chiral copper sulfide nanoflowers, specifically including the following steps: S1: To prepare a copper sulfide colloidal solution, weigh 340 mg (2 mmol) CuCl2·2H2O and dissolve it in 60 mL of ultrapure water. Add the solution to a 200 mL beaker, add 4.0 g of PVP-K30, and stir magnetically until the solid is completely dissolved (the solution turns light blue). Stir at 1500 rpm and slowly add 10 mL of a 17 wt% (NH4)2S solution. After the addition, the solution turns dark brown (primary CuS crystal nuclei begin to form). Continue stirring magnetically for 30 min to obtain the copper sulfide colloidal solution.

[0047] S2: Preparation of copper sulfide nanosheets. The entire S1 colloidal solution was transferred to a 100 mL PTFE-lined stainless steel high-pressure reactor. The reactor was placed stably in a forced-air drying oven, and the reaction temperature was set to 180℃. The reaction was carried out at this constant temperature for 12 h. After the reaction, the reactor was allowed to cool naturally to room temperature. The reaction product was transferred to a 50 mL centrifuge tube and centrifuged at 12000 rpm for 15 min. The supernatant was discarded. Deionized water was added to the precipitate for redispersion, followed by centrifugation and washing. This washing step was repeated three times to thoroughly remove free ligands and inorganic byproducts. The final collected black precipitate was frozen and then dried in a vacuum freeze dryer for 20 h to obtain a dried solid powder sample, i.e., copper sulfide nanosheets.

[0048] S3: Preparation of chiral copper sulfide nanoflowers: 20 mg of copper sulfide nanosheets were dissolved in 20 mL of ultrapure water and placed in a magnetic stirrer at 800 rpm. 10 mL of 0.5 M chiral ligand L-Arg was slowly added, and the mixture was stirred for 24 h. The reaction product was transferred to a 50 mL centrifuge tube and centrifuged at 12000 rpm for 15 min. The supernatant was discarded. Deionized water was added to the precipitate for redispersion, followed by centrifugation and washing. This washing step was repeated three times to thoroughly remove free ligands and inorganic byproducts. The collected black precipitate was frozen and dried in a vacuum freeze dryer for 20 h to obtain a dried solid powder sample, i.e., chiral copper sulfide nanoflowers.

[0049] Example 4 This embodiment provides performance characterization of copper sulfide nanoflower samples.

[0050] 1. Circular dichroism (CD) spectrum Chiral copper sulfide nanoflowers protected by different ligands in Example 1 were characterized using circular dichroism (CD) spectroscopy. Figure 1 , Figure 2 ), and calculate the absorption asymmetry factor based on the test data ( Figure 3 , Figure 4 ).

[0051] Depend on Figure 1 As shown in a and b, in the ultraviolet band (180~350 nm), the peaks of L-Arg NFs and D-Arg NFs appear at 200 nm and ~250 nm, with broadened peak shapes and lower intensity (±5 mdeg). L-His NFs and D-His NFs exhibit high-intensity, sharp positive and negative mirror peaks (ellipticity up to ±10 mdeg) at 195 nm and 213 nm. Regardless of whether histidine or arginine is used, the CD spectra of L-type and D-type samples are symmetric about the zero axis, indicating that the macroscopic chiral optical activity is entirely derived from the spatial configuration of the ligands.

[0052] Depend on Figure 1 As shown in 'c', in the visible and near-infrared bands (400~1000 nm), the CD spectra of L-Arg NFs and D-Arg NFs exhibit broadened chiral response peaks at 550~700 nm. This directly corresponds to the chiral optical response of chiral inorganic nanostructures, and its signal source is completely different from that of small molecule ligands. The core is the resonant coupling between the chiral geometry and light of a specific wavelength. Notably, L- / D-Arg NFs exhibit distinct positive and negative mirror peaks at 590 nm and 753 nm. Arginine molecules selectively bind to the CuS surface through their guanidine groups, inducing slight helical twisting or chiral deformation of the nanosheets during growth. This chiral geometry causes differences in the absorption of left-handed and right-handed circularly polarized light by in-plane oscillating electrons, resulting in a distinct CD signal near 590 nm. When multiple nanosheets are assembled into three-dimensional nanoflowers, arginine regulates the relative orientation and twisting angle during the assembly process through intermolecular interactions, thus exhibiting the characteristic signal of a chiral superstructure at 753 nm, which also reflects the synergistic twisting between nanosheets.

[0053] Depend on Figure 1As shown in d, in the visible and near-infrared bands (400~1000 nm), L- / D-His NFs exhibit a combination of "one large and two small" symmetrical peaks at 435 nm, 570 nm, and 693 nm. The strong CD peak at 693 nm mainly originates from chiral plasmon coupling at the CuS-sulfur (S) heterointerface. When chiral histidine is adsorbed at the CuS@S heterointerface, its chirality can induce chiral optically active transfer at the metal sites. Due to the presence of the heterointerface, this chiral transfer efficiency is greatly enhanced, hence the dominant strong peak at 693 nm. The peak at 570 nm corresponds to the in-plane plasmon resonance of a single CuS nanosheet. This signal is relatively weak. Compared to arginine-induced CuS nanoflowers, the shifts in the chiral plasmon resonance peak and plasmon coupling peak directly reflect the regulatory effect of the chiral inducer and material composition on the chiral optical response. The CD peak at nm may originate from the charge transfer transition between CuS and elemental S. Electrons at the CuS@S heterostructure interface transfer from sulfur to copper ions. This charge transfer process will appear as a shorter wavelength signal in the CD spectrum. Elemental sulfur acts as a bridge for chiral transfer. The chirality of histidine is first transferred to the CuS surface and then to the elemental sulfur phase through the CuS-S interface. In this process, elemental sulfur further amplifies and stabilizes the chiral optical activity through its flexible electronic structure.

[0054] Depend on Figure 2 It can be seen that all samples exhibit a significant Cotton effect in the wavelength range of 180–280 nm, and the signal in this region mainly originates from the π-π junctions of chiral amino acid ligands. / n-π Electronic transitions confirmed that the chiral ligands were successfully modified onto the surface of CuS nanomaterials, maintaining their chirality. However, no significant chiral signal was detected in the CuS nanomaterials protected by these four pairs of ligands within the wavelength range of 350–1000 nm, indicating that chirality failed to be successfully transferred to the inorganic core of the nanostructure. The core reason for this difference is the different strengths and modes of the chiral ligand-nanosurface interaction. The transfer of chirality from molecules to inorganic nanomaterials requires an efficient "interfacial coupling." The imidazole group of chiral His and Cu... 2+ Strong coordination, the guanidinium group of chiral Arg and S 2- / Cu 2+ Through multiple binding processes, both types of ligands can firmly and directionally bind to the CuS surface, thereby inducing chiral twisting of the nanosheets and achieving chiral signal transduction. Furthermore, the secondary amine of Pro, the carboxyl and hydroxyl groups of Tra, and the carboxyl group of Glu bind to Cu... 2+The binding force of cys is relatively weak, and it cannot trigger the twisting of individual nanosheets or the chiral torsional assembly of nanosheets during the assembly process. Cys contains thiol groups (-SH), which have a strong binding force with copper sulfide nanosheets through S-Cu covalent bonds, and can induce small nanosheets to grow into larger nanosheets, but it cannot produce chiral assembly. Furthermore, Cys does not couple with the localized surface plasmon resonance (LSPR) effect, so there is no chiral signal in the near-infrared region. In addition, chiral transfer requires ligands to form an ordered, oriented self-assembled monolayer on the surface. The cyclic structure of proline and the flexible molecular configuration of tartaric acid and glutamic acid may affect the ordered arrangement of ligands on the CuS surface, resulting in the inability to effectively transfer chiral information to the inorganic core.

[0055] Depend on Figure 3 The L / D curves show opposite signs in the main peak region, indicating that the chiral optical response of Arg NFs and His NFs is still dominated by ligand configuration. L-Arg NFs exhibit a distinct positive peak in the short-wavelength ultraviolet region, roughly at 200 nm, followed by a rapid decline and a weak negative value maintained in the longer wavelength region. This strong positive peak indicates that L-Arg has a high unit absorption chiral response in the ultraviolet region, mainly due to Arg ligand-related electronic transitions and the induced absorption asymmetry after interaction with the CuS surface. The guanidino, amino, and carboxyl groups in the Arg molecule can interact with copper sites on the CuS surface, creating an asymmetric distribution of the local electronic environment, thereby amplifying the g-factor signal in the short-wavelength region. The red line for D-Arg NFs mainly shows a weak negative response in the same wavelength range, with a shallow negative peak in the short-wavelength region, gradually approaching the zero axis. Compared to L-Arg NFs, D-Arg NFs exhibit significantly lower peak intensities, indicating that although the two enantiomers have opposite chiral orientations, their normalized responses in this UV region are not completely equal in amplitude. This may be related to the sample absorption intensity, the degree of local ligand coverage, or the nanofiber dispersion state. Since the g-factor is sensitive to absorbance values, the curve is more prone to amplified fluctuations when absorption is weak in a certain wavelength band.

[0056] Depend on Figure 4It can be seen that all four groups of samples exhibit a major g-factor response between 180 and 250 nm, indicating that this band corresponds to the intrinsic electronic transitions of the ligands and the induced response after the ligands interact with the CuS surface. The L-type and D-type curves are roughly mirror images of each other in the main peak region, indicating that the direction of the absorption asymmetry factor is mainly determined by the absolute configuration of the ligands, rather than by random aggregation or testing errors. The signal of each group weakens significantly after 250 nm, indicating that the effective chiral response of these samples is mainly concentrated in the ultraviolet region, with no obvious chiral signal in the long wavelength range. The differences between different ligands are mainly reflected in the peak shape and intensity. Cys and Pro both show obvious positive-to-negative conversion. Cys relies on the formation of Cu-S interaction between the thiol group and the copper site, and the chiral transfer is more biased towards local interfacial coordination; Pro relies on the rigid ring structure to restrict the conformation, making the L / D mirror image more regular. Tra has the widest g-factor peak and the most prominent intensity, indicating that multi-point coordination or hydrogen bond network is beneficial to amplifying the chiral response under unit absorption. The weakest signal from Glu indicates that although the flexible dicarboxylic acid ligands can adsorb onto the CuS surface, their surface arrangement is relatively dispersed, limiting the chiral amplification effect. Overall, the functional group type, molecular rigidity, and surface binding mode collectively determine the peak position, intensity, and L / D mirror image degree of the g-factor.

[0057] 2. Ultraviolet-Vis absorption spectrum (UV-Vis) UV-Vis detection was performed on the samples ( Figure 5 , Figure 6 The position and intensity of the absorption peak of the sample are determined, the interband transition characteristics of semiconductors and near-infrared localized surface plasmon resonance (LSPR) behavior are analyzed, and the evolution of the optical band gap and free carrier concentration of the material is inferred.

[0058] Depend on Figure 5It can be seen that the L-type and D-type curves in the UV-Vis-NIR absorption spectra basically overlap, indicating that the two enantiomer samples are consistent in chemical composition, crystal structure, and optical absorption energy levels. Both Arg NFs and His NFs exhibit significant UV absorption and broad visible-near-infrared absorption. The absorption in the 180–350 nm region is mainly related to the ligands themselves and the electronic transitions after coordination on their surfaces, while the 350–1000 nm region reflects more the broadband absorption, layer stacking, and near-infrared light response of the CuS-based nanostructure. The main difference between Arg NFs and His NFs lies in the peak shape and long-wavelength absorption characteristics in the UV region. Arg NFs exhibit a rapid decline followed by a low absorption plateau in the 180–350 nm range, with a relatively simple peak shape, indicating that its UV response mainly comes from guanidinium, amino, and carboxyl group-related transitions and the absorption background after interaction with the CuS surface. His NFs exhibit a more pronounced shoulder peak around 200–210 nm, indicating that imidazole groups participate in ultraviolet electronic transitions and influence the electronic environment of the CuS surface. In the 350–1000 nm range, both types of samples show a broad absorption trend of first decreasing and then increasing, but His NFs show a more significant plateau in the mid-band and near-infrared enhancement, which may be related to imidazole group coordination, nanosheet stacking, or CuS / S interface interactions.

[0059] In summary, both Arg and His can effectively modulate the light absorption behavior of CuS nanoflowers, enabling them to respond in the ultraviolet, visible, and near-infrared regions. Among them, the Arg system exhibits more uniform and stable broadband absorption characteristics, while the His system shows more obvious interface transitions and near-infrared enhancement characteristics.

[0060] Depend on Figure 6It is observed that L-Cys NFs exhibit strong absorption near 180 nm, which then rapidly decreases with increasing wavelength, entering a low absorption region close to the baseline after approximately 220–230 nm. This change indicates that Cys-related electronic transitions are mainly concentrated in the deep ultraviolet region. Since the Cys molecule contains -SH, -NH2, and -COOH groups, the thiol groups readily form Cu-S interactions with copper sites on the CuS surface, fixing the ligands to the nanofiber surface. The strong absorption in the short-wavelength region can be attributed to the electronic transitions of the Cys ligands and their surface coordination, and also includes the absorption contribution of the CuS nanostructure in the ultraviolet region. The D-Cys NFs curve largely overlaps with the L-Cys NFs, also showing strong absorption near 180 nm, followed by rapid decay, and maintaining a low absorption level after 230 nm. The two curves do not exhibit the mirror image relationship seen in CD spectra because ordinary absorption spectroscopy only reflects the total absorption of incident light by the material and does not distinguish between left and right circularly polarized light. The absorption curves of L / D-Cys are highly similar, indicating that the nanofibers induced by the two enantiomers are not significantly different in terms of composition, concentration, size distribution, and fundamental electronic transitions. Their main differences should lie in the chiral optical response, rather than in the conventional absorption peak positions.

[0061] 3. X-ray diffraction (XRD) XRD detection was performed on different samples. Figure 7 The characteristic diffraction peak positions and full width at half maximum (FWHM) of the sample are determined to identify the phase of the synthesized product, and it is analyzed whether the chiral ligand-induced self-assembly process causes lattice distortion or grain size changes.

[0062] Depend on Figure 7 It can be seen that PVP NFs are CuS@S heterostructures. The diffraction peaks at 15.4°, 23.1°, and 27.8° correspond to the (113), (222), and (040) crystal planes of the S standard card (JCPDS No. 08-0247), respectively, while the diffraction peaks at 47.9° and 59.3° correspond to the (110) and (116) crystal planes of the CuS standard card (JCPDS No. 06-0464), respectively. In addition, the CuS characteristic peaks in PVP NFs are relatively broad and weak, indicating that their crystallinity and degree of ordered orientation of crystal planes are relatively limited. This shows that PVP can achieve basic morphological stability and heterostructure construction, but its ability to control phase purification and selective growth of crystal planes is weak.

[0063] Depend on Figure 7It can be seen that the main diffraction peak positions and intensity distributions of L-Arg NFs are basically consistent with those of the standard card of hexagonal copper sulfide (JCPDS No. 06-0464), located at characteristic peaks of 27.7°, 29.3°, 31.8°, 32.8°, 47.9°, 52.7° and 59.3°, corresponding to the (101), (102), (103), (006), (110), (108) and (116) crystal planes of CuS, respectively. It is worth noting that the modification of chiral ligand L-Arg completely eliminates the signal of elemental sulfur, indicating that chiral Arg molecules can preferentially interact with elemental sulfur in CuS@S heterostructure: its abundant -NH2 and guanidinyl groups act as nucleophiles, attacking the SS bonds in the heterostructure, converting insoluble elemental sulfur into soluble polysulfides or thioorganic compounds, thereby selectively etching away the sulfur component from the heterostructure interface. With the removal of sulfur (S), the lattice interstices previously occupied by S are transformed into vacancy defects, simultaneously exposing the pure hexagonal CuS phase. Since the S "de-intercalation" process does not destroy the CuS framework structure, its diffraction peak positions and intensity distribution remain highly consistent with the standard card of hexagonal copper sulfide. Furthermore, the synergistic coordination of carboxyl and guanidine groups in the Arg molecule further stabilizes the CuS surface, preventing lattice collapse, thus achieving integrated "chemical etching-vacancy creation" control of multi-component sulfide heterostructures by chiral ligands.

[0064] Depend on Figure 7 It can be seen that the XRD diffraction peaks at 18.4° and 28.3° of the L-Cys NFs sample correspond to the (10-2) and (102) crystal planes of the cysteine ​​standard card (JCPDS No. 42-1370), and only a weak CuS signal was observed in this sample. This is mainly attributed to the simultaneous presence of -NH2, -COOH, and -SH functional groups in the L-Cys molecule, among which the thiol group has a significant impact on CuS. 2+ L-Cys exhibits strong affinity, enabling it to form stable metal-organic complexes through Cu-S coordination. Furthermore, L-Cys molecules can self-assemble via hydrogen and disulfide bonds, forming a dense organic network structure that encapsulates or isolates the small amount of CuS particles within the amorphous matrix, resulting in severe attenuation or even annihilation of their diffraction signals. Therefore, only characteristic diffraction peaks attributable to the crystalline L-Cys itself are observed in the XRD pattern, and a distinct hexagonal CuS phase cannot be detected. This result further indicates that the coordination ability of thiol-based chiral ligands directly determines the nucleation and growth behavior of the inorganic phase in the copper-sulfur system.

[0065] Depend on Figure 7 It is known that L-Tra NFs, L-Glu NFs, and L-His NFs are all CuS@S heterostructures, and the S content varies in copper sulfide nanoflowers protected by different ligands. Figure 7As shown in b, the intensity ratio of the diffraction peaks of S (222) and CuS (110) changes. Compared with PVP NFs, the CuS content in L-Glu NFs is reduced, while the S content in L-Tra NFs and L-His NFs is significantly reduced. Further analysis reveals that this difference mainly stems from the different interaction mechanisms between the functional groups of each ligand side chain and the CuS@S heterointerface: excess L-Glu (containing two -COOH and one -NH2) interacts with CuS. 2+ Formation of stable glutamic acid-copper complex, reducing free Cu 2+ The concentration decreases, thus reducing the CuS content and causing a slight increase in the S / CuS ratio in the overall heterostructure; adjacent hydroxyl groups of L-Tra (containing two -COOH and two -OH) can be partially deprotonated to form -O. - As a weak nucleophile, it attacks the -SS- bonds in the CuS@S heterostructure to form soluble polysulfides or thiosulfates, promoting the dissolution of elemental sulfur; L-His (containing an imidazole ring, -NH2, and -COOH) forms nucleophilic N - His directly attacks the SS bond, dissolving elemental sulfur. However, the efficiency of His nucleophilic attack may be affected by steric hindrance and is weaker than the polyhydroxy synergistic effect of Tra. Therefore, the content of S is between that of PVP NFs and L-Tra NFs.

[0066] 4. X-ray photoelectron spectroscopy (XPS) XPS detection was performed on different samples ( Figures 8-13 The chemical element valence state composition of the sample surface was analyzed, the chemical state distribution of Cu, S and ligand characteristic elements (N, O) was resolved, the anchoring mode and interfacial coordination environment of chiral amino acids on the nanosheet surface were revealed, and the physicochemical basis of chiral signal transduction was elucidated.

[0067] Depend on Figure 8 It can be seen that the CC peak dominates on the sample surface, and the organic carbon skeleton mainly originates from the carbon chains in the ligand molecules. The C1s spectrum of L-Cys NFs has only two peaks, attributed to CC and CN respectively. This may be because L-Cys is firmly adsorbed on the CuS surface through the -SH group, causing the carboxyl group (O=C-OH) at the end of the molecule to adhere tightly to the substrate. Its photoelectron signal is strongly attenuated by the substrate and difficult to detect. Only the contributions from CC and CN species in the upper part of the molecule are clearly observed in the C1s spectrum. In contrast, the CC peak in the control sample PVP NFs mainly originates from the PVP-K3 molecule.

[0068] Depend on Figure 9 It can be seen that the peaks located near 931.6 eV and 951.2 eV correspond to Cu, respectively. + 2p 3 / 2 and 2p 1 / 2The binding energy, while the peaks near 932.2 eV and 951.6 eV are attributed to Cu, respectively. 2+ 2p 3 / 2 and 2p 1 / 2 Binding energy. Because in hexagonal CuS, the tetrahedral sites correspond to Cu... 2+ The center, and the triangular site corresponds to Cu + The center, therefore copper exhibits Cu + With Cu 2+ A mixed dual oxidation state. (From) Figure 10 It can be seen that with the change of ligand type, Cu + 2p 3 / 2 With Cu 2+ 2p 3 / 2 The binding energies all underwent varying degrees of shift, indicating that the ligands modulated the electron cloud density around the copper center through electron donor or acceptor effects. For example, in the presence of strongly coordinating ligands (such as the guanidinium group in L-Arg), Cu... 2+ Cu + The proportion of binding ions increases significantly, and the binding energy shifts towards higher binding energies. This is attributed to the strong electron-donating ability of the guanidinium group, which reduces the electron cloud density of the copper site by substituting for S coordination (N is more electronegative than S), leading to a blue shift in the XPS binding energy. While the imidazole group in the L-His side chain can also coordinate via nitrogen, it lacks a strong back-bonding π bond, thus its binding energy remains unchanged. The thiol group in L-Cys has a stronger binding affinity for copper ions, but the binding of excess ligands leads to a significant decrease in the Cu signal. L-Tra and L-Glu primarily bind via the carboxyl group (-COO). - The oxygen atom coordinates with copper. Oxygen has high electronegativity and provides a lone pair of electrons when coordinating with copper, making it a pure σ-donor. Therefore, electrons are transferred to copper, increasing the electron density of the copper ion. 2+ Cu + The binding energy is reduced. The above valence state distribution and binding energy shift law indicate that the ligand can effectively regulate the electronic structure and defect state of copper on the surface of copper sulfide nanomaterials by controlling the oxidation state balance of copper.

[0069] Depend on Figure 11 It can be seen that the S 2p fine energy spectrum of CuS nanomaterials can be decomposed into four main components, which are respectively attributed to Cu-S, S-S, and S-S. 2- (SS) 2- And high-valence sulfur-SO. Among them, the Cu-S peak represents sulfur at low-coordination or defect sites on the surface. In the CuS system, due to the presence of copper and Cu... + and Cu 2+ In mixed valence states, the electron cloud density of the Cu-S bond is relatively high, therefore the binding energy is slightly lower than that of the conventional S bond. 2- S 2- Belonging to the normal monosulfide ion in the crystal lattice, and Cu +or Cu 2+ Ionic bonds are formed and are one of the main components of the CuS bulk phase. (SS) 2- The corresponding disulfide ion, with its SS covalent bond, leads to a decrease in the electron cloud density of the sulfur atom, further indicating that the material is a CuS crystalline phase. -SO belongs to the sulfate ions (SO4) formed by oxidation on the material surface. 2- or sulfite SO3 2- This indicates that partial surface oxidation occurred in the sample during the testing process. Notably, only one pair of peaks appeared in the L-Cys NFs, which may indicate that the L-Cys molecules form "solid-SS-molecule" disulfide bonds through surface sulfur atoms, and the excessive Cys ligands masked other S signals.

[0070] Depend on Figure 12 It can be seen that, compared with PVP NFs, the relative content of sulfur valence states on the surface of CuS NFs modified by various amino acids changed significantly, reflecting the selective regulatory effect of different ligands on the chemical state of CuS surface. Specifically, the S2 content in PVP NFs... 2- It accounted for the highest proportion (69.8%), and also contained a certain amount of S. 2- (21.7%), its surface is dominated by SS covalent bonds, consistent with the characteristics of hexagonal CuS. In L-His NFs, the imidazole groups have strong coordination ability, which may induce more sulfur to exist stably as surface-coordinated sulfur through the coordination of N atoms with surface copper ions, while some S 2- Displaced or dissolved. The guanidinium group of L-Arg is a strong electron-donating ligand, which can promote the increase of electron cloud density in Cu-S bonds, causing some S2 to be displaced or dissolved. 2- Restore to S 2- Meanwhile, the degree of surface oxidation increases slightly. In L-Tra NFs, the carboxyl coordination of tartaric acid helps clean the surface and stabilize some S-Cu coordination bonds. In L-Glu NFs, the carboxyl coordination ability of glutamic acid is weak, and its overall effect on the surface is small. The proportions of each component are closest to those of PVP NFs. In particular, L-Cys molecules undergo oxidative coupling on the CuS NFs surface to form cystine, and its SS bond signal completely masks other signals, indicating that L-Cys greatly alters the sulfur chemical state of the CuS surface.

[0071] Depend on Figure 13 It can be seen that the surface elemental composition of CuS NFs modified with different ligands exhibits significant differences. The Cu content of Cys NFs was much lower than that of other samples, while the S content was at a moderate level, and the O content was the highest. This is attributed to the fact that the thiol group (-SH) of the cysteine ​​side chain readily reacts with Cu. 2+Strong coordination and even redox reactions can occur, leading to competitive desorption of surface copper ions or the formation of soluble complexes, exposing more carboxyl and hydroxyl groups. In contrast, L... Arg NFs exhibited the highest Cu and S content, which was mainly attributed to the guanidino group (-C(NH2)). 2+ The strong electrostatic adsorption of metal ions; while L His NFs have a significantly higher N content than the PVP control, consistent with the structural characteristic of histidine imidazole rings containing two nitrogen atoms. Glu NFs have the highest C content, reflecting the carbon-rich characteristics of the carboxyl groups in the glutamic acid side chain. L The presence of N in Tra NFs suggests that the CuS surface still contains a small amount of PVP. The difference in these elemental ratios demonstrates that the functional groups of different ligands (thiol, imidazole, guanidinyl, carboxyl) achieve precise tailoring of the chemical composition of the CuS NFs surface by adjusting the surface coordination environment, charge density, and steric hindrance.

[0072] Example 5 This embodiment provides a chiral regulation mechanism for copper sulfide nanoflower samples modified with different ligands.

[0073] The basic properties of the six chiral ligands are shown in Table 1. The geometric structure and charge distribution of the six chiral ligands were analyzed using PyMOL software. Red corresponds to the negative charge region, and blue corresponds to the positive charge region. The results are as follows: Figure 14 As shown.

[0074] Table 1. Basic properties of six chiral ligands

[0075] Table 1 shows that different ligands exhibit significant differences in side-chain functional groups, pKa, isoelectric point, charge state, and water solubility. These parameters collectively determine their adsorption, coordination, and chirality-inducing abilities on the CuS NFs surface. From a coordination chemistry perspective, side-chain groups are crucial for regulating Cu... 2+ The core of adsorption and sulfur valence state. The thiol group (-SH) of Cys belongs to a soft base, and is associated with the soft acid Cu. + Cu 2+ The formation of extremely strong covalent coordination bonds leads to surface Cu 2+ Competition for desorption occurs, and the thiol group is readily oxidized to form disulfide bonds or thiosulfates, resulting in a large number of sulfur vacancies. The imidazole group of His (pKa ≈ 6.0~6.8) is partially protonated at neutral pH, allowing it to bond with Cu via the N atom on the imidazole ring. 2+A stable chelate structure is formed, and the surface copper-sulfur network is moderately retained. The guanidino group of Arg (pKa≈12.5) is completely positively charged at pH=7, and it firmly captures the negatively charged copper-sulfur complex in solution through electrostatic attraction. Therefore, its Cu and S contents are the highest, and it has a high proportion of reduced sulfur and few sulfur vacancies on the surface. In contrast, Glu and Tra contain only carboxyl groups (-COOH) and hydroxyl groups (-OH), and their composition is similar to Cu. 2+ Its coordination ability is relatively weak, and its direct intervention in the copper-sulfur network is relatively small.

[0076] Depend on Figure 14 It can be seen that the guanidino group of L-Arg exhibits a large-scale dark blue positively charged region, which allows it to preferentially anchor to the negatively charged sulfur sites on the surface through electrostatic attraction, forming a stable "positive-negative" interfacial dipole moment, which is beneficial for the effective transmission of chiral information; the area near the thiol group of L-Cys is a locally negatively charged region (red), which interacts with the positively charged Cu on the CuS surface. + Cu 2+ Strong electrostatic attraction occurs at the sites; however, this attraction is over-enhanced by the strong covalent coordination of the thiol group, leading to the extraction of copper ions and disrupting the chiral origin of the surface lattice. The imidazole ring of L-His exhibits partial delocalization of the π-electron cloud and an alternating distribution of positive and negative charges, enabling it to interact with Cu... 2+ Coordination occurs, and the sulfur can interact with adjacent sulfur through hydrogen bonds, thus stabilizing the surface configuration in both directions. After the carboxyl groups of L-Glu and L-Tra dissociate, they become negatively charged as a whole. They generate electrostatic repulsion with the negatively charged sulfur sites on the CuS surface. Therefore, they mainly rely on hydrogen bonds or van der Waals forces for loose adsorption, resulting in low chiral transfer efficiency.

[0077] His side chain imidazole group, terminal amino group, and carboxyl group together form a tripentate coordination system, which can interact with Cu on the CuS surface. 2+ Stable five- or six-membered chelate rings are formed at the sites. This multi-point anchoring not only firmly fixes the chiral center (Cα) at ​​a distance of approximately 0.4–0.6 nm from the surface, but also induces a small but regular chiral distortion in the surface lattice by generating moderate feedback π bonds between the π electrons of the imidazole ring and the d orbitals of copper ions. Simultaneously, His's isoelectric point (pI = 7.64) carries almost no net charge at neutral pH, avoiding excessive electrostatic repulsion or disordered adsorption orientation. Therefore, His molecules uniformly cover the nanoflower surface in a nearly "upright" conformation, and chiral information is effectively transferred to the entire inorganic framework through electronic coupling, generating a strong CD signal.

[0078] The guanidino group of Arg is fully protonated at pH 7, carrying a single positive charge, and forms a strong electrostatic attraction with the negatively charged sulfur sites on the surface. Simultaneously, the three NH₂ groups of the guanidino group can form hydrogen bond networks with adjacent sulfur or lattice oxygen, resulting in multi-site adsorption. This mode allows the Arg molecule to maintain an "upright" conformation, with the chiral center far from the substrate (approximately 0.7 nm), without disrupting the original oxidation state equilibrium of CuS. The blue shift of the Cu 2p binding energy in XPS confirms the transfer of electrons from the guanidino group to the copper sites; this electron-donating effect further amplifies the surface chiral optical activity. Therefore, the Arg-modified sample also exhibits a strong CD signal.

[0079] The thiol groups of Cys form extremely strong thiolate covalent bonds with surface copper ions, causing the ligand molecules to adhere tightly to the CuS surface in a "flat" configuration. Although the binding strength is extremely high, the chiral center (Cα) is pulled close to the substrate (<0.3 nm), and its asymmetric configuration is shielded by surface metal ions, making it difficult to transfer to the lattice. More seriously, the strong reducing power of the thiol groups leads to a decrease in the surface Cu... 2+ The crystalline structure undergoes extensive competitive desorption (Cu content drops to 0.45 at%), triggering a surge in sulfur vacancies and disrupting the high degree of order in the original lattice, preventing the formation of chiral distortions. Therefore, the Cys-modified sample exhibits no CD signal.

[0080] Although Pro is a cyclic imino acid, its secondary amine ring cannot react with Cu. 2+ Stable chelation is mainly achieved through monodentate carboxyl adsorption, resulting in weak binding strength, random adsorption configuration, and an inability of chiral centers to align neatly on the surface. Both Glu and Tra contain only carboxyl groups (and hydroxyl groups), classifying them as hard base ligands, and react with soft acids like Cu. + / Cu 2+ The binding constants of these ligands are low, relying mainly on loose attachment through hydrogen bonding or electrostatic repulsion. The ligand molecules are in a "lying and sliding" state on the surface, unable to fix and transmit chiral information. Therefore, none of these three types of ligands induced measurable CD signals.

[0081] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A chiral copper sulfide nanomaterial, characterized in that, The chiral copper sulfide nanomaterial is a chiral ligand-modified copper sulfide nanomaterial. The chiral ligand is arginine or histidine; The chiral copper sulfide nanomaterial exhibits circular dichroism spectral response in the ultraviolet, visible, and near-infrared bands, and chiral plasmon response in the visible and near-infrared bands.

2. The chiral copper sulfide nanomaterial according to claim 1, characterized in that, The arginine is L-arginine or D-arginine; The histidine is L-histidine or D-histidine; The wavelength range of the ultraviolet band is 180~350 nm; The wavelength range of the visible and near-infrared bands is 400~1000 nm.

3. The method for preparing the chiral copper sulfide nanomaterial according to any one of claims 1 to 2, characterized in that, include: The chiral ligand was prepared into a 0.1-0.5 M solution to obtain a chiral ligand solution; The chiral ligand solution was added to an aqueous solution of copper sulfide nanomaterials, stirred, and centrifuged to precipitate the chiral copper sulfide nanomaterials.

4. The preparation method according to claim 3, characterized in that, The volume ratio of the chiral ligand solution to the mass ratio of the copper sulfide nanomaterial is 1:0.5~2.

5. The preparation method according to claim 3, characterized in that, The stirring speed is 800 rpm, and the stirring time is 24 h; The centrifugation speed is 6000~12000 rpm, and the centrifugation time is 15 min.

6. The preparation method according to claim 3, characterized in that, Dissolve CuCl2·2H2O in water, add PVP-K30, stir magnetically until the solid dissolves, then add (NH4)2S solution and continue stirring magnetically to obtain a copper sulfide colloidal solution. The copper sulfide colloidal solution was reacted in a reaction vessel, and the reaction product was centrifuged. The precipitate was the copper sulfide nanomaterial.

7. The preparation method according to claim 6, characterized in that, The mass ratio of CuCl2·2H2O to PVP-K30 is 0.085~0.34:4; The concentration of the (NH4)2S solution is 17 wt%, and the molar volume ratio of CuCl2·2H2O to the (NH4)2S solution is 0.5~2:1~10.

8. The preparation method according to claim 6, characterized in that, The magnetic stirring speed is 1500 rpm, and the magnetic stirring time is 30 min. The reaction temperature in the reactor is 180℃, and the reaction time is 12 h. The reaction product was centrifuged at a speed of 6000~12000 rpm for 15 min.

9. The application of the chiral copper sulfide nanomaterials according to any one of claims 1 to 2 in circularly polarized light detection.

10. The application of the chiral copper sulfide nanomaterials according to any one of claims 1 to 2 in chiral photoelectric detection.

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