Inorganic nanoparticle array with ultra-narrow surface-lattice resonance and large-area preparation method thereof

Abstract

The application relates to an inorganic nanoparticle array with super-narrow surface lattice resonance and a large-area preparation method thereof, which comprises the following steps: a centimeter-level silicon nanopillar stamp is used to mold a polydimethylsiloxane nanopore array template; the nanopore array template is dipped into a polymer organic solution, and then the nanopore array template is placed on a surface-hydroxylated silicon wafer to form close contact; after the solvent is completely volatilized, a polymer nanopillar array is obtained; metal precursors are adsorbed on the polymer surface through electrostatic action, and the metal ions are reduced by oxygen plasma and the polymer is etched, finally, through thermal annealing, the inorganic nanoparticle array with super-narrow surface lattice resonance is obtained. Compared with the prior art, the application provides a low-cost and high-efficiency universal platform for the preparation of the inorganic nanoparticle array, and makes the large-scale preparation of the next generation of nanophotonic and electronic devices possible.

Description

Technical Field

[0001] This invention relates to the field of micro-nano fabrication technology, specifically to an inorganic nanoparticle array with ultra-narrow surface lattice resonance and its large-area fabrication method. Background Technology

[0002] Plasmatic, magnetic, and semiconductor inorganic nanoparticles have attracted considerable attention from researchers due to their unique optical, magnetic, electronic, chemical, and catalytic properties. Among them, plasmatic nanoparticles, with their localized surface plasmon resonance (LSPR) effect, have become one of the most powerful platforms for controlling light-matter interactions, effectively coupling light to nanostructures and compressing it into subwavelength volumes. These locally excited effects, accompanied by significant near-field enhancement, enable plasmatic nanoparticles to have wide applications in sensing, nanophotonics, photochemistry, and nonlinear optics. However, energy loss, primarily radiative attenuation, in individual plasmatic nanoparticles results in a wide peak width (typically greater than 80 nm) and a low quality factor (Q factor) in LSPR resonances, severely limiting their applications in nanolasers and sensing. Effectively reducing energy loss by lowering Landau damping (damping of collision-free collective oscillation modes) or plasmon energy damping originating from collisions between electrons and other electrons, defects, and phonons remains a significant challenge.

[0003] One effective method to reduce radiation loss is to arrange plasmonic nanoparticles into periodic arrays to achieve excitation-surface lattice resonance (SLR) of a hybrid mode. The SLR mode is the coupling between the diffraction mode of the periodic array structure and the LSPR mode between individual nanoparticles, supporting an ultranarrow plasmonic resonance linewidth theoretically limited to 1-2 nm. However, achieving such a narrow linewidth experimentally is not easy, mainly due to the difficulty in fabricating periodic array structures with precisely positioned and defect-free nanoparticles. Bottom-up self-assembly techniques using nanoscale chemical or topological templates can arrange highly homogeneous, size- and composition-tunable wet-synthesized nanoparticles into ordered arrays, but the precision of nanoparticle arrangement within the array is quite limited. The reason for the low precision is that high yield and high precision are contradictory requirements for the relative particle size and nanoscale pattern size during particle assembly. In contrast, top-down techniques based on template metal deposition can fabricate plasmonic arrays with narrow linewidths. However, this approach involves expensive, complex, and time-consuming processes (e.g., fabrication of gold nanopore arrays via template metal deposition, mask metal deposition through nanopore arrays, and high-temperature thermal annealing), all of which heavily rely on cleanrooms and specialized equipment. Furthermore, while nanoparticle arrays with uniform size and shape can be fabricated using metal ion reduction in nanodomains after block copolymer phase separation or dip-pen nanoimprinting, this technique is difficult to scale to large areas and offers limited control over the lattice parameters of the array structure (such as periodicity, symmetry, and nanoparticle size). In summary, there is an urgent need for a simple, flexible, and precise method to fabricate high-quality, large-area inorganic nanoparticle arrays with narrow linewidths and high Q-factors. Summary of the Invention

[0004] The purpose of this invention is to overcome at least one of the defects of the prior art and provide a simple, flexible, precise, narrow-linewidth, high-Q-factor inorganic nanoparticle array with ultra-narrow surface lattice resonance and its large-area preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] The preparation method of this invention is mainly based on solvent-assisted soft lithography, in-situ metal reduction, and thermal annealing. We can use this technology to prepare a series of metal (such as Au, Pd, and Pt), metal alloy (such as AuPd, FePt, and CoPt), and metal oxide (such as Fe2O3 and CoO2) nanoparticle arrays. The array area reaches the centimeter scale, and the nanoparticles have smooth surfaces and uniform shapes.

[0007] This preparation method is very stable and highly flexible: the diameter of the nanoparticles can be adjusted by changing the height of the polymer nanoarray, and the lattice parameters (e.g., the geometric symmetry and periodicity of the lattice) can be controlled by the template used.

[0008] The fabricated array is virtually defect-free and exhibits extremely high periodicity, thus possessing exceptionally superior optical properties. Taking a gold nanoparticle array as an example, surface lattice resonance with a linewidth of approximately 4 nm and a Q-factor of approximately 218 can be achieved. The specific scheme is as follows:

[0009] A method for large-area fabrication of inorganic nanoparticle arrays with ultra-narrow surface lattice resonance, comprising the following steps:

[0010] A polydimethylsiloxane (PDMS) nanoporous array template was obtained by using a centimeter-scale silicon nanopillar stamp for molding.

[0011] After dipping the nanopore array template into the polymer organic solution, the nanopore array template is placed on the surface hydroxylated silicon wafer to form a close contact. After the solvent has completely evaporated, a polymer nanopillar array is obtained.

[0012] Metal precursors are adsorbed onto the polymer surface using electrostatic interactions, and the metal ions are reduced and the polymer is etched away using oxygen plasma. Finally, thermal annealing is used to obtain an array of inorganic nanoparticles with ultra-narrow surface lattice resonance.

[0013] Furthermore, the size of the silicon nanopillar stamp is (0.1-5.0) × (0.1-5.0) cm. 2 For example, 0.1 × 0.1 cm 2 0.2×0.2cm 2 0.3×0.3cm 2 0.4×0.4cm 2 0.5×0.5cm 2 0.6×0.6cm 2 0.7×0.7cm 2 0.8×0.8cm 2 0.9×0.9cm 2 1.0×1.0cm 2 1.1×1.1cm 2 1.2×1.2cm 2 1.3×1.3cm 2 1.4×1.4cm 2 1.5×1.5cm 2 1.6×1.6cm 2 1.7×1.7cm 2 1.8×1.8cm2 1.9×1.9cm 2 2.0×2.0cm 2 2.1×2.1cm 2 2.2×2.2cm 2 2.3×2.3cm 2 2.4×2.4cm 2 2.5×2.5cm 2 3.0×3.0cm 2 4.0×4.0cm 2 5.0×5.0cm 2 .

[0014] Furthermore, the silicon nanopillar stamps have a tetragonal or hexagonal lattice array with a period of 100-2000 nm, such as 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, and 2000 nm. The nanopillar diameters are 100-300 nm, such as 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, and 210 nm. nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, and nanopillar heights of 100-400nm, such as 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 370nm, 380nm, 390nm, 400nm.

[0015] Furthermore, the polymers in the polymer organic solution include polytetravinylpyridine (P4VP), polydivinylpyridine (P2VP), polyacrylic acid (PAA), poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), polyvinyl alcohol (PVA), polyethylene oxide (PEO), or polystyrene sulfonic acid (PSSA); the solvents include isopropanol, ethanol, methanol, acetone, butanone, tetrahydrofuran, dichloromethane, chloroform, hexane, or cyclohexane.

[0016] Furthermore, the polymer mass fraction in the polymer organic solution is 0.2-4.8%, for example, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, 3.6%, 3.8%, 4.0%, 4.2%, 4.4%, 4.6%, and 4.8%.

[0017] Furthermore, before adsorbing the metal precursor, the polymer nanopillar array is pretreated with oxygen plasma for 2-45 s, such as 2 s, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, and 45 s.

[0018] Furthermore, the metal precursor is chloroauric acid (HAuCl4·3H2O), potassium ferricyanide [K3Fe(CN)6], sodium chloropalladium (Na2PdCl4), potassium cobalt cyanide [K3Co(CN)6], or potassium chloroplatinate (K2PtCl4).

[0019] Furthermore, the oxygen pressure of the oxygen plasma is 10-100 mtorr, such as 10 mtorr, 20 mtorr, 30 mtorr, 40 mtorr, 50 mtorr, 60 mtorr, 70 mtorr, 80 mtorr, 90 mtorr, and 100 mtorr; the gas flow rate is 15-60 s.ccm, such as 15 s.ccm, 20 s.ccm, 25 s.ccm, 30 s.ccm, 35 s.ccm, 40 s.ccm, 45 s.ccm, 50 s.ccm, 55 s.ccm, and 60 s.ccm; and the power is 20-80 W, such as 60 W.

[0020] Furthermore, the aforementioned hot annealing adopts a three-step hot annealing process, specifically as follows: first, the temperature is raised from room temperature to 500℃ within 1 hour and held for 2 hours. After naturally cooling to room temperature, the temperature is then raised to 700℃ within 1 hour and held for 2 hours. After naturally cooling to room temperature again, the temperature is finally raised to 1000℃ within 1 hour and held for 2 hours before naturally cooling down; or annealing is performed at 800℃ for 2 hours in an Ar atmosphere.

[0021] An inorganic nanoparticle array with ultra-narrow surface lattice resonance, prepared by the large-area preparation method described above, includes a metal nanoparticle array, including Au, Pd or Pt; a metal alloy nanoparticle array, including AuPd, FePt or CoPt; and a metal oxide nanoparticle array, including Fe2O3 or CoO2.

[0022] Compared with existing technologies, especially existing "top-down" nanofabrication technologies, the present invention has at least the following advantages:

[0023] (1) This invention can easily and quickly replicate multiple centimeter-scale nanoparticle arrays from a template at the same time;

[0024] (2) The present invention does not rely on cleanroom facilities or special equipment, such as electron beam etching (EBL) and metal deposition equipment, and is therefore time and cost-effective;

[0025] (3) This invention is applicable to the preparation of different metal, intermetallic compound alloy and metal oxide nanoparticle arrays;

[0026] (4) The nanoparticles obtained by this invention have uniform size and shape, high crystallinity, smooth surface, and exhibit excellent optical properties. Attached Figure Description

[0027] Figure 1 SEM images and size distribution maps (AC) of gold nanoparticle arrays with different diameters in Example 1 are shown.

[0028] Figure 2 Characterization of the alloy nanoparticle array prepared in Example 2. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0030] An inorganic nanoparticle array with ultra-narrow surface lattice resonance and its large-area fabrication method are detailed below:

[0031] A polydimethylsiloxane nanoporous array template was obtained by using a centimeter-scale silicon nanopillar stamp for molding; the size of the silicon nanopillar stamp was (0.1-5.0) × (0.1-5.0) cm. 2 The lattice type is a tetragonal or hexagonal array with a period of 100-2000 nm, the diameter of the nanopillars is 100-300 nm, and the height of the nanopillars is 100-400 nm.

[0032] A 1% (w / w) polymer solution was prepared by dissolving the polymer in an organic solvent. A PDMS template was then immersed in the polymer solvent for 10 seconds, and subsequently placed onto a pretreated, hydroxylated silicon wafer to form a tight contact. The polymers in the organic solution included polytetravinylpyridine (P4VP), polydivinylpyridine (P2VP), polyacrylic acid (PAA), poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), polyvinyl alcohol (PVA), polyethylene oxide (PEO), or polystyrene sulfonic acid (PSSA); the solvents included isopropanol, ethanol, methanol, acetone, butanone, tetrahydrofuran, dichloromethane, chloroform, hexane, or cyclohexane.

[0033] Pretreatment is a very common surface treatment technique, commonly known as piranha solution cleaning. (This information is from...)

[0034] https: / / ehs.princeton.edu / laboratory-research / chemical-safety / chemical-specific-pro tocols / piranha-solutions

[0035] After 30 minutes, the solvent completely evaporated, yielding a polymer nanopillar array. Subsequently, a metal precursor was adsorbed onto the polymer surface using electrostatic interactions, and the metal ions were reduced and the polymer etched away using oxygen plasma. Finally, thermal annealing was used to obtain the desired inorganic nanoparticle array. The metal precursors were chloroauric acid (HAuCl4·3H2O), potassium ferricyanide [K3Fe(CN)6], sodium chloropalladium (Na2PdCl4), potassium cobalt cyanide [K3Co(CN)6], or potassium chloroplatinate (K2PtCl4). The oxygen plasma had an oxygen pressure of 10-100 mtorr, a gas flow rate of 15-60 s·ccm, and a power of 20-80 W.

[0036] Example 1

[0037] The synthesis of a tetragonal array of gold nanoparticles is detailed below:

[0038] A PDMS nanoporous array template was obtained by using a centimeter-scale tetragonal silicon nanopillar stamp for molding. A 1% (w / w) P4VP organic solution was prepared, and the PDMS template was immersed in the P4VP solution for 10 seconds. Then, the PDMS template was placed on a pre-treated silicon wafer with a hydroxylated surface to form a tight contact. After 30 minutes, the solvent completely evaporated, resulting in a P4VP nanopillar array. Subsequently, the P4VP nanopillars were treated with oxygen plasma at an oxygen pressure of 60 mtorr, a flow rate of 35 s·ccm, and a power of 60 W.

[0039] Next, the P4VP array was immersed in a 3 mM HAuCl4 aqueous solution for 1 hour, then rinsed with deionized water, dried with N2 gas, and treated with oxygen plasma at the previously set parameters for 4 minutes to completely remove the polymer P4VP, thus obtaining a gold nanocluster array. Finally, a three-step thermal annealing method was used to form a monodisperse gold nanoparticle array: first, the temperature was raised from room temperature to 500℃ within 1 hour and held for 2 hours, then allowed to cool naturally to room temperature, then the temperature was raised to 700℃ within 1 hour and held for 2 hours, then allowed to cool naturally to room temperature again, and finally the temperature was raised to 1000℃ within 1 hour and held for 2 hours, followed by natural cooling.

[0040] Specifically, the height of the P4VP array was first adjusted by controlling the reactive ion beam etching time, which in turn affected the precursor loading and thus controlled the diameter of the obtained gold nanoparticles. Specifically, when the oxygen plasma treatment time was 10 s, 15 s, and 20 s, the heights of the P4VP array were 210 nm, 190 nm, and 167 nm, respectively, and the diameters of the obtained gold nanoparticles were 94 nm, 84 nm, and 70 nm, respectively.

[0041] Figure 1 SEM images and size distribution maps (AC) of gold nanoparticle arrays with different diameters are shown. It can be seen that the nanoparticle size distribution is relatively uniform, with a standard deviation of less than 9%.

[0042] Example 2

[0043] The difference from Example 1 is that,

[0044] For the preparation of Pd and Pt nanoparticle arrays, P4VP nanopillar arrays were immersed in a 3% (w / w) HCl solution of 1 mM Na2PdCl4 and 1 mM K2PtCl4 for 30 min.

[0045] For AuPd alloy nanoparticle arrays, P4VP nanopillar arrays were immersed in a 3% (w / w) HCl solution of 0.35 mM Na2PdCl4 and 0.65 mM HAuCl4 for 30 min.

[0046] For FePt alloy nanoparticle arrays, P4VP nanopillar arrays were immersed in a 3% (w / w) HCl solution of 0.35 mM K3Fe(CN)6 and 0.5 mM K3Co(CN)6 for 30 min.

[0047] For the CoPt alloy nanoparticle array, the P4VP nanopillar array was immersed in a 3% (w / w) HCl solution of 0.4 mM K3Co(CN)6 and 0.6 mM K2PtCl4 for 30 min.

[0048] The mixture was then annealed at 800°C for 2 hours under an Ar atmosphere. The other steps were the same as in Example 1.

[0049] Figure 2 For alloy nanoparticle arrays. (AC) SEM images of different alloy arrays Au-Pd (A), Fe-Pt (B), and Co-Pt (C). (DI) Representative scanning transmission electron (STEM) images and corresponding energy dispersive spectroscopy (EDS) images (D, F, H) and high-resolution transmission electron microscopy (HRTEM) images (E, G, I) of different alloy arrays Au-Pd (D, E), Fe-Pt (F, G), and Co-Pt nanoparticles (H, I).

[0050] In summary, this invention combines solvent-assisted soft lithography and in-situ, site-specific growth, enabling the efficient fabrication of inorganic nanoparticle arrays without the need for cleanrooms or specialized equipment. As a demonstration, a gold nanoparticle array was fabricated, achieving an ultra-narrow lattice resonance peak with a linewidth of 4 nm and a quality factor of 218, approaching the theoretical limit. This work provides a low-cost and high-efficiency general platform for the fabrication of inorganic nanoparticle arrays, making the large-scale fabrication of next-generation nanophotonic and electronic devices possible.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for large-area fabrication of inorganic nanoparticle arrays with ultra-narrow surface lattice resonance, characterized in that, The method includes the following steps: A polydimethylsiloxane nanoporous array template was obtained by using a centimeter-scale silicon nanopillar stamp for molding. After dipping the nanopore array template into the polymer organic solution, the nanopore array template is placed on the surface hydroxylated silicon wafer to form a close contact. After the solvent has completely evaporated, a polymer nanopillar array is obtained. Metal precursors are adsorbed onto the polymer surface using electrostatic interactions, and the metal ions are reduced and the polymer is etched away using oxygen plasma. Finally, thermal annealing is used to obtain an array of inorganic nanoparticles with ultra-narrow surface lattice resonance.

2. The method for large-area fabrication of an inorganic nanoparticle array with ultra-narrow surface lattice resonance according to claim 1, characterized in that, The dimensions of the silicon nanopillar stamp are (0.1-5.0) × (0.1-5.0) cm. 2 .

3. The method for large-area fabrication of an inorganic nanoparticle array with ultra-narrow surface lattice resonance according to claim 1, characterized in that, The silicon nanopillar stamps have a lattice type of tetragonal or hexagonal array with a period of 100-2000 nm, a nanopillar diameter of 100-300 nm, and a nanopillar height of 100-400 nm.

4. The method for large-area fabrication of an inorganic nanoparticle array with ultra-narrow surface lattice resonance according to claim 1, characterized in that, The polymers in the polymer organic solution include polytetravinylpyridine, polydivinylpyridine, polyacrylic acid, N,N-dimethylaminoethyl methacrylate, polyvinyl alcohol, polyethylene oxide, or polystyrene sulfonic acid; the solvents include isopropanol, ethanol, methanol, acetone, butanone, tetrahydrofuran, dichloromethane, chloroform, hexane, or cyclohexane.

5. The method for large-area fabrication of an inorganic nanoparticle array with ultra-narrow surface lattice resonance according to claim 1, characterized in that, The polymer mass fraction in the polymer organic solution is 0.2-4.8%.

6. The method for large-area fabrication of an inorganic nanoparticle array with ultra-narrow surface lattice resonance according to claim 1, characterized in that, Before adsorbing the metal precursor, the polymer nanopillar array is pretreated with oxygen plasma for 2-45 s.

7. The method for large-area fabrication of an inorganic nanoparticle array with ultra-narrow surface lattice resonance according to claim 1, characterized in that, The metal precursors are chloroauric acid, potassium ferricyanide, sodium chloropalladium, potassium cobalt cyanide, or potassium chloroplatinate.

8. The method for large-area fabrication of an inorganic nanoparticle array with ultra-narrow surface lattice resonance according to claim 1, characterized in that, The oxygen pressure of the oxygen plasma is 10-100 mtorr, the gas flow rate is 15-60 s·ccm, and the power is 20-80 W.

9. The method for large-area fabrication of an inorganic nanoparticle array with ultra-narrow surface lattice resonance according to claim 1, characterized in that, The heat annealing process is a three-step process: first, the temperature is raised from room temperature to 500℃ within 1 hour and held for 2 hours. After naturally cooling to room temperature, the temperature is then raised to 700℃ within 1 hour and held for 2 hours. After naturally cooling to room temperature again, the temperature is raised to 1000℃ within 1 hour and held for 2 hours before naturally cooling down.

10. An inorganic nanoparticle array with ultra-narrow surface lattice resonance prepared by the large-area preparation method according to any one of claims 1-9, characterized in that, The nanoparticle array includes a metal nanoparticle array, including Au, Pd or Pt; a metal alloy nanoparticle array, including AuPd, FePt or CoPt; and a metal oxide nanoparticle array, including Fe2O3.

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