A nano-cluster structure for improving light absorption efficiency

Abstract

The application discloses a kind of nanocluster structures for improving light absorption efficiency, to provide a kind of nanocluster structure with stable high absorption efficiency under near-infrared light irradiation.The present application is based on the random agglomeration of nanochip cap structure monomer that only grows connecting molecule on cap surface, weaken the dependence of nanocluster structure on incident light polarization state;By wrapping the connecting surface into the cluster structure, reduce the contact between the connecting surface and the outside world, limit the number of particles in the cluster structure, limit the absorption spectrum widening of cluster structure by using the plasmonic coupling between limited particles, improve the light absorption efficiency of nanocluster structure.Based on the nanoprobes of the nanocluster structure have wide application prospect in photothermal therapy, biosensing, drug delivery and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials and nanoprobe technology, and in particular relates to a nanocluster structure that improves light absorption efficiency. Background Technology

[0002] With the rapid development of nanotechnology, nanophotothermal therapy has shown promising prospects in the treatment of malignant tumors. Nanophotothermal therapy utilizes the light absorption properties of nanophotothermal agents to convert light energy into heat energy, increasing the ambient temperature to induce cancer cell death. With the intervention of nanophotothermal agents, photothermal therapy can precisely target tumors, minimizing damage to surrounding healthy tissues. Compared with traditional treatments such as chemotherapy and radiotherapy, photothermal therapy has advantages such as reducing patient suffering, shortening treatment time, improving treatment efficacy, and reducing toxic side effects, making it a highly effective emerging therapy in the field of cancer treatment.

[0003] When applying light to tissues, a suitable optical window is crucial, requiring not only avoidance of overlap with the absorption spectra of other tissue components but also sufficient penetration depth. Studies have shown that the 700-1300 nm near-infrared band is an ideal optical window, thus requiring the peak absorption wavelength of the photothermal nanoparticles to be within this band to achieve optimal photothermal conversion efficiency. Noble metal nanoparticles, due to their unique Localized Surface Plasmon Resonance (LSPR) characteristics, can convert absorbed light energy into heat energy, making them an important type of photothermal nanoparticle. Conventionally shaped spherical noble metal nanoparticles typically have absorption peaks far below 600 nm for individual particles. In applications, they often aggregate, utilizing the LSPR resonance coupling between multiple particles to redshift the absorption spectrum to the near-infrared band. However, the symmetrical spherical particles exhibit a single LSPR mode, and aggregation of multiple particles is accompanied by multi-body chain coupling. Furthermore, the interaction surface between particles is a full-circumference spherical surface, making it difficult to control the number of particles in the aggregate, resulting in severe broadening of the aggregate absorption spectrum and a significant impairment in the excitation photothermal conversion efficiency.

[0004] To address the aforementioned issues, this invention proposes a cluster structure based on a nanocore-cap structure to improve light absorption efficiency. The nanocore-cap structure consists of a spherical core covered by a metal cap. Compared to spherical nanoparticles, the nanocore-cap structure, which breaks spherical symmetry, splits the single LSPR mode of the spherical particle into two main modes: an electric dipole and a magnetic dipole, corresponding to the excitation light polarization directions parallel and perpendicular to its symmetry axis, respectively. The electric field distributions of the two modes are along the axial and cap-edge directions, respectively. The absorption peak wavelength of the electric dipole mode is shorter; by adjusting the core-to-shell ratio, the absorption peak corresponding to the magnetic dipole mode can be significantly redshifted to the near-infrared band. Research has found that the interaction between two closely spaced nanocore-cap structures originates from hybridization between different modes. Depending on the relative spatial orientation of the two particles, they can undergo plasma hybridization through magnetic dipole-magnetic dipole, magnetic dipole-electric dipole, and electric dipole-electric dipole coupling, thereby causing a shift in the resonance peak. In the near-infrared band, the absorption peak mainly originates from the electric field present at the cap rim. When two nanocore-cap structure monomers are connected side-by-side along the cap rim, the coupling effect between magnetic dipoles causes the maximum redshift of the resonance absorption peak. When the two deviate from this extreme position, they are connected through the cap-shaped metal shell, and the interaction between magnetic dipoles gradually weakens to the contribution of the monomers. In clusters composed of randomly aggregated multiparticles, the nanocore-cap structure monomers are interconnected through connecting molecules on the surface of the cap-shaped metal shell. The curvature of the connecting surface limits the number of aggregates and the hybridization intensity, thereby compressing the full width at half maximum (FWHM) of the absorption peak, eliminating the dependence on the polarization direction of the excitation light, and improving the utilization rate of the excitation light. Summary of the Invention

[0005] The technical problem this invention aims to solve is to provide a nanocluster structure that improves light absorption efficiency. Utilizing the structural characteristics and LSPR properties of the nanocore-cap structure monomers, the invention restricts the number of monomer clusters and limits the interaction modes between particles through a curved spherical growth surface, thereby compressing the broadening of the near-infrared spectrum and reducing dependence on the polarization direction of the excitation light. This structure is not only suitable for photothermal agents but can also be used as a probe for target recognition and imaging.

[0006] The technical solution of this invention is as follows:

[0007] A nanocluster structure for improving light absorption efficiency is as follows:

[0008] The nanocluster structure is composed of n nanocore-cap structure monomers randomly agglomerated by connecting molecules grown on the outer surface of the cap, where n≥2; the nanocore-cap structure monomer is composed of a spherical core and a cap-shaped metal shell covering its outer surface, wherein the spherical core is a dielectric material, the cap-shaped metal shell is made of a noble metal with local surface plasmon resonance effect, the cap-shaped metal shell has a coverage of less than or equal to 50% of the surface of the spherical core, and the connecting molecules are grown on the outer surface of the cap-shaped metal shell;

[0009] In the aforementioned nanocluster structure, the connecting molecules act only on the cap-shaped metal shell. The nanocore-cap structure monomers are connected and aggregated to each other through the cap-shaped metal shell, wrapping the connecting surface inside the cluster structure to reduce the contact between the connecting surface and the outside, thus limiting the number of monomers in the formed nanocluster structure.

[0010] The nanocap structure exhibits different local surface plasmon resonance modes in directions parallel and perpendicular to the axis of symmetry, namely, electric dipole mode and magnetic dipole mode. The nanocluster structure compresses the redshift of the resonance peak between the magnetic dipole-magnetic dipole modes between adjacent monomers by means of the bending of the connecting surface. On this basis, the broadening of the absorption spectrum of the nanocluster structure in the near-infrared band is limited by the plasmon resonance coupling between a finite number of monomer spherical surfaces, so as to improve the light absorption efficiency.

[0011] In the aforementioned nanocluster structure, the nanocore-cap structure monomers randomly aggregate on a three-dimensional freeform surface, which reduces the dependence on the polarization state of the incident light and improves the utilization rate of light absorption.

[0012] The connecting molecules can be the same or complementary. The nanocap structure monomers can be connected through the two ends of the same connecting molecule or through the interaction between the connecting molecules.

[0013] The number of aggregates of the nanocap structure monomers is affected by the density of the connecting molecules.

[0014] In the aforementioned nanocap structure monomer, no connecting molecules grow on the external dielectric material to enhance the independence of the cluster structure and stabilize absorption performance.

[0015] The optical performance of the nanocluster structure that improves light absorption efficiency depends on the geometric parameters of the nanocore-cap structure monomer. By adjusting parameters such as the core radius, shell thickness, and noble metal material of the nanocore-cap structure monomer, it can be adapted to different wavelength bands.

[0016] The beneficial effects of this invention are as follows: This invention utilizes multiple nano-core-cap structure monomers with connecting molecules growing only on the outer surface of the cap to randomly aggregate into a nanocluster structure. By enclosing the connecting surface inside the cluster structure, the contact between the connecting surface and the outside world is reduced, limiting the number of monomers in the cluster structure. The plasmonic resonance coupling between a finite number of nano-core-cap structure monomers restricts the broadening of the absorption spectrum of the nanocluster structure in the near-infrared band. At the same time, the random aggregation of nano-core-cap structure monomers ensures that the nanocluster has magnetic dipole components in all directions, reducing the dependence on the polarization state of incident light. This structure not only solves the problem of absorption spectrum broadening of nanocluster structures and improves light absorption efficiency, but also provides a nanocluster structure that reduces the dependence on the polarization state of incident light, improving light absorption utilization. This structure can be used not only as a photothermal agent, but also as a probe for target recognition and imaging. Nanoprobes based on this nanocluster structure have broad application prospects in photothermal therapy, biosensing, and drug delivery. Attached Figure Description

[0017] Figure 1 This is the LSPR absorption spectrum of the nanocap structure monomer.

[0018] Figure 2 The upper limit of the redshift of the LSPR absorption peak is caused by the magnetic couple chain bonding coupling mode.

[0019] Figure 3 The lower limit of the LSPR absorption peak is caused by the parallel bonding coupling mode of magnetic dipoles.

[0020] Figure 4 This is the LSPR absorption spectrum of a nanocluster structure formed by the random aggregation of nanocore-cap structure monomers. Detailed Implementation

[0021] To better describe the present invention, embodiments have been described in detail with reference to the accompanying drawings and technical solutions. It should be emphasized that the following descriptions are merely illustrative and should not limit the scope and application of the present invention.

[0022] Figure 1The LSPR absorption spectrum of the nanocore-cap structure monomer is shown. The core of this nanocore-cap structure is a 60 nm diameter SiO2 sphere, covered by a 5 nm thick gold shell, forming a semi-shell-shaped cap structure. Excitation light is incident along the negative z-axis, with its polarization direction making an angle θ with the positive x-axis. The components parallel and perpendicular to the x-axis form two distinct LSPR absorption peaks at 645 nm and 890 nm. The peak at 890 nm increases rapidly with increasing θ, and the absorption performance of the nanocore-cap structure monomer is optimal when θ = 90°. This embodiment proposes a nanocluster structure based on this nanocore-cap structure monomer to improve light absorption efficiency. This cluster structure has the following characteristics:

[0023] i) The nanocluster structure is formed by the random aggregation of n (n≥2) nanocore-cap structure monomers after the growth of connecting molecules on the outer surface of the cap; the nanocore-cap structure monomer is composed of a spherical core and a cap-shaped metal shell covering its outer surface, wherein the spherical core is a dielectric material, the cap-shaped metal shell is made of a noble metal with local surface plasmon resonance effect, the cap-shaped metal shell has a coverage rate of 50% on the surface of the core, and the connecting molecules grow on the outer surface of the cap-shaped metal shell;

[0024] In the nanocluster structure described in ii), the connecting molecules only act on the cap-shaped metal shell part. The nanocore cap structure monomers are connected and aggregated to each other through the connecting molecules on the metal cap, wrapping the connecting surface inside the cluster structure to reduce the contact between the connecting surface and the outside, thus limiting the number of monomers in the formed cluster structure.

[0025] iii) such as Figure 1 The absorption peak of the nanocore-cap structure monomer in electric dipole mode is located at 645 nm, and the absorption peak in magnetic dipole mode is located at 890 nm. The coupling modes between particles in the nanoclusters formed by the random aggregation of nanocore-cap structure monomers include electric dipole-electric dipole, electric dipole-magnetic dipole, and magnetic dipole-magnetic dipole coupling. The near-infrared absorption peak in the magnetic dipole coupling mode is of particular interest. The electric field vibration of the magnetic dipole is concentrated at the cap rim. When adjacent core-cap monomers are connected to each other via the cap rim, such as... Figure 2As shown, the magnetic dipoles are connected end-to-end in a bonding coupling mode (mode ①) to achieve dipole hybridization, causing the LSPR peak to redshift to the upper limit of 1230 nm. In mode ②, the cap edge and top of the nanocore-cap structure monomers are connected, representing a bonding coupling between a magnetic dipole and an electric dipole, with the corresponding LSRP wavelength at 990 nm. Both of these connection positions are special extreme positions, unlikely to form naturally during actual wet fabrication (a low-probability event). The analysis of the interaction modes in the figure clarifies the strongest interaction modes between magnetic dipoles and between magnetic dipoles and electric dipoles. When monomers aggregate using molecules on the metal spherical shell surface, since there are far more molecules on the shell surface than at the cap edge, clustering is highly likely to occur on the shell surface outside the cap edge. The curvature of the spherical surface breaks the chain-like bonding coupling mode in mode ①, compressing the redshift. As the monomer connection positions gradually move away from the above extreme positions, the distance between the cap edges of the monomers increases, the coupling effect decreases, and it gradually tends to return to the independent magnetic dipole interaction mode of the nanocore-cap structure monomers. Figure 3 As shown, under a 90° polarized incident direction (perpendicular to the paper), all three monomers in the cluster structure are in magnetic dipole mode. The corresponding LSPR absorption peak is at 855 nm. In this mode (mode ③), the magnetic field vibrations couple in a parallel, side-by-side bonding manner. Due to the large distance between the cap rim planes, the coupling effect is weak, and the blue shift is slight, essentially approximating the LSPR of a single monomer (890 nm). This mode determines the lower limit of the redshift in the absorption wavelength of the nanocluster structure. As the polarization angle decreases, the effect of the surface electric field of adjacent monomers on the nanocluster structure decreases, gradually tending towards independent magnetic dipole interaction between the nanocluster structure monomers. At a polarization angle of 0°, the absorption wavelength is 880 nm, approximately the wavelength of independent magnetic dipole interaction between the nanocluster structure monomers. Figure 4 The diagram shows a nanocluster structure composed of randomly aggregated nanocore-cap structure monomers. The absorption peak at 885 nm is mainly formed by the independent magnetic couple interaction of the nanocore-cap structure monomers, while the absorption peak at 1070 nm is mainly formed by the bonding coupling between magnetic couples of the nanocore-cap structure monomers. The wavelengths of the two absorption peaks are between 855 and 1230 nm. In actual fabrication, the nanocore-cap structure monomers randomly aggregate into nanocluster structures with different numbers of monomers and different postures. Under excitation light irradiation, the absorption spectra of each cluster structure superimpose, resulting in broadened absorption peaks, with the width limited to the upper and lower limits.

[0026] In the nanocluster structure described in iv), the nanocore cap structure monomers are randomly aggregated on a three-dimensional freeform surface, and magnetic dipole components of the nanocore cap structure monomers exist in all directions, which reduces the dependence of the nanocluster structure on the polarization state of the incident light and improves the utilization rate of light absorption.

Claims

1. A nanocluster structure for improving light absorption efficiency, characterized in that: The nanocluster structure is composed of n nanocore-cap structure monomers randomly agglomerated by connecting molecules grown on the outer surface of the cap, where n≥2; the nanocore-cap structure monomer is composed of a spherical core and a cap-shaped metal shell covering its outer surface, wherein the spherical core is a dielectric material, the cap-shaped metal shell is made of a noble metal with local surface plasmon resonance effect, the coverage of the cap-shaped metal shell on the surface of the spherical core is less than or equal to 50%, and the connecting molecules are grown on the outer surface of the cap-shaped metal shell; In the aforementioned nanocluster structure, the connecting molecules act only on the cap-shaped metal shell. The nanocore-cap structure monomers are connected and aggregated to each other through the cap-shaped metal shell, wrapping the connecting surface inside the cluster structure to reduce the contact between the connecting surface and the outside, thus limiting the number of monomers in the formed nanocluster structure. The nanocap structure exhibits different local surface plasmon resonance modes in directions parallel and perpendicular to the axis of symmetry, namely, electric dipole mode and magnetic dipole mode. The nanocluster structure compresses the redshift of the resonance peak between magnetic dipole-magnetic dipole modes between adjacent monomers by means of the bending of the connecting surface. The broadening of the absorption spectrum of the nanocluster structure in the near-infrared band is limited by the plasmon resonance coupling between a finite number of monomer spherical surfaces.

2. The nanocluster structure for improving light absorption efficiency according to claim 1, characterized in that, The connecting molecules are the same or complementary, and the nanocap structure monomers are connected through the two ends of the same connecting molecule or through the interaction between the connecting molecules.

3. A nanocluster structure for improving light absorption efficiency according to claim 1 or 2, characterized in that, In the aforementioned nanocap structure, no connecting molecules grow on the exposed external dielectric material.

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