Reaction pathway and free-energy barrier for reactivation of dimethylphosphoryl-inhibited human acetylcholinesterase

Surface modification of the laser powder bed-fused Ti-Zr-Nb scaffolds by dynamic chemical etching and Ag nanoparticles decoration

Metallic lattice scaffolds are designed to mimic the architecture and mechanical properties of bone tissue and their surface compatibility is of primary importance. This study presents a novel surface modification protocol for metallic lattice scaffolds printed from a superelastic Ti-Zr-Nb alloy. This protocol consists of dynamic chemical etching (DCE) followed by silver nanoparticles (AgNP) decoration. DCE, using an 1HF + 3HNO3 + 12H2O23% based solution, was used to remove partially-fused particles from the surfaces of different as-built lattice structures (rhombic dodecahedron, sheet gyroid, and Voronoi polyhedra). Subsequently, an antibacterial coating was synthesized on the surface of the scaffolds by a controlled (20 min at a fixed volume flowrate of 500 mL/min) pumping of the functionalization solutions (NaBH4 (2 mg/mL) and AgNO3 (1 mg/mL)) through the porous structures. Following these treatments, the scaffolds' surfaces were found to be densely populated with Ag nanoparticles and their agglomerates, and manifested an excellent antibacterial effect (Ag ion release rate of 4-8 ppm) suppressing the growth of both E. coli and B. subtilis bacteria up to 99 %. The scaffold extracts showed no cytotoxicity and did not affect cell proliferation, indicating their safety for subsequent use as implants. A cytocompatibility assessment using MG-63 spheroids demonstrated good attachment, spreading, and active migration of cells on the scaffold surface (over 96 % of living cells), confirming their biotolerance. These findings suggest the promise of this surface modification approach for developing superelastic Ti-Zr-Nb scaffolds with superior antibacterial properties and biocompatibility, making them highly suitable for bone implant applications.

Effect of hot electron induced charge transfer generated by surface plasmon resonance on Ag@Au/ITO/PNTP systems

The present study discusses the fabrication of a bimetallic material consisting of silver nanorods and gold nanospheres (designated Ag@Au), and its surface modification with 4-nitrothiophenol (PNTP) after deposition on an indium tin oxide (ITO) glass sheet, followed by laser irradiation at various wavelengths. The results indicate that the reduction of PNTP is more complete under irradiation at 532 nm due to the surface plasmon resonance (SPR) effects of the gold and silver nanomaterials. Moreover, the surface enhanced Raman scattering (SERS) of the PNTP adsorbed on the Ag@Au/ITO is found to be significantly stronger than that of PNTP adsorbed on Ag@Au alone, due to charge transfer (CT) at the interface. In addition, the SERS enhancement effect of the PNTP molecules on the Ag@Au/ITO substrate is optimal under 532 nm laser irradiation due to the hot electron-induced CT generated by the SPR effect. Thus, the system constructed herein combines the effects of SPR and CT, thereby assisting in a further understanding of the enhancement mechanism of SERS and, hence, the further development SERS research in metal-semiconductor-molecular systems.

Ag decoration on Na2Ti3O7 nanowires for improved SERS and PHE performance

Na2Ti3O7 (NTO) is recognized as an authenticated promising photocatalyst and surface-enhanced Raman scattering (SERS) active material, although its performance is limited by its high carrier recombination rate, wide band gap and inadequate utilization of visible light. In this study, to solve these issues, sea urchin-shaped NTO nanowires directly grown on a substrate were fabricated, and then Ag nanoparticles were decorated on NTO nanowires using sputtering equipment. The as-prepared Ag-NTO substrates exhibited different morphologies and high SERS activity, which was confirmed by finite-difference time-domain (FDTD) simulations, showing that appropriate Ag decoration can bring more nanogaps and thus enhance the electromagnetic field (EM) contribution. We visualized the charge transfer (CT) mechanism in SERS and further investigated the catalytic hydrogen production process similarly induced by photogenerated CT. The optimal SERS substrate (Ag-NTO-3) was adopted to verify the photocatalytic hydrogen evolution (PHE) activity, and the hydrogen evolution rate of Ag-NTO-3 was 106.7 μmol h-1 (twice that of pristine NTO). Photoelectrochemical measurements and photoluminescence (PL) analysis were used to elucidate the potential enhancement mechanisms for the photocatalytic performance and CT process. This study can provide a valuable reference for performance and mechanism studies of SERS substrates and photocatalysts.

Selective Thermal and Photocatalytic Decomposition of Aqueous Hydrazine to Produce H2 over Ag-Modified TiO2 Nanomaterial

An Ag-modified TiO₂ nanomaterial was prepared by a one-pot synthesis method using tetra butyl titanate, silver nitrate, and sodium hydroxide in water at 473 K for 3 h. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to determine the structure and morphology of the synthesized Ag-modified TiO₂ nanomaterial. The diffuse reflectance UV-visible and photoluminescence spectroscopy results revealed that metallic Ag nanoparticles decreased the optical band gap and photoluminescence intensity of the TiO₂. In addition, the Raman peak intensity and absorbance were increased after Ag modification onto TiO₂. The photocatalytic efficiency of the synthesized samples was tested for decomposition of aqueous hydrazine solution under visible light irradiation. The photocatalytic efficiency of Ag-modified TiO₂ nanomaterials was higher than that of bare TiO₂ and Ag metal NPs due to the synergistic effect between the Ag metal and TiO₂ structures. In addition, the surface plasmon resonance (SPR) electron transfer from Ag metal particles to the conduction band of TiO₂ is responsible for superior activity of TiO₂-Ag catalyst. The Ag-modified TiO₂ nanomaterials offered a 100% H₂ selectivity within 30 min of reaction time and an apparent rate constant of 0.018 min^-1 with an activation energy of 34.4 kJ/mol under visible light radiation.

Fabrication of sandwich structures of Ag/analyte/MoO3sea urchins for SERS detection of methylene blue dye molecules

A substrate for surface-enhanced Raman spectroscopy (SERS) in a sandwich configuration, noble metal/analyte/defect-rich metal oxide, is demonstrated for the detection of methylene blue(MB). The sandwich structure (Ag/MB/SUMoO₃) is fabricated by physical vapour deposition of Ag nanoparticles over the MB analytes that are adsorbed on sea urchin MoO₃(SUMoO₃). SUMoO₃are grown on a glass substrate by chemical bath deposition. The morphology of the fabricated sandwich structures shows serrated spikes of MoO₃from the core region decorated with strings of silver nanoparticles. The silver-decoration and the oxygen defects of SUMoO₃promote absorption in the visible region and facilitate charge transfer between MB and SUMoO₃, which are beneficial for achieving superior SERS properties in this configuration compared to the contribution from individual components alone. The sandwich structure is able to detect the MB molecule up to 100 nM with an enhancement factor of 8.1 × 10⁶. The relative standard deviation of SERS intensity for the 1618 cm^-1peak of MB across the substrate is 29.2%. The configuration offers stability to SERS substrate under ambient conditions. The combined effect of charge transfer, surface plasmon resonance, and MB resonance results in the improved SERS detection of MB molecules with the Ag/MB/SUMoO₃sandwich structure.

Plasmonic Enhanced SERS in Ag/TiO2 Nanostructured Film: An Experimental and Theoretical Study

In this work, we present a new study on the electromagnetic (EM) enhancement properties generated by Ag/TiO₂ toward the finger print of methylene blue (MB) molecules deposited on the surface of Ag nanostructures. SERS intensity generated by MB molecules reflects the interaction between the local electric field and their bonds. A power-dependent SERS study in order to reveal the magnitude effect of a local electric field on the vibration behavior of molecular bonds of MB was performed. A theoretical study using finite element (COMSOL Multiphysics) was performed in order to understand the effect of interparticle distance of Ag nanoparticles on the enhancement properties.

Irradiation-Induced Synthesis of Ag/ZnO Nanostructures as Surface-Enhanced Raman Scattering Sensors for Sensitive Detection of the Pesticide Acetamiprid

Detecting pesticides using techniques that involve simple fabrication methods and conducting the detection at very low levels are challenging. Herein, we report the detection of acetamiprid at the quadrillionth level using surface-enhanced Raman scattering (SERS). The SERS chip comprises Ag nanoparticles deposited on a tetrapod structure of ZnO coated onto indium tin oxide glass (denoted as Ag@ZnO-ITO). Controlled Ag decoration of ZnO occurs via irradiation-induced synthesis. The morphology of the surface plays a significant role in achieving an enhanced SERS performance for acetamiprid detection. 4,4'-Dipyridyl (DPY) is used to investigate synthesis conditions for the chip, leading to an optimal irradiation time of 60 min. Furthermore, the enhancement factor for acetamiprid on Ag@ZnO-ITO is higher than 10⁷. These results demonstrate that SERS sensors have the potential for practical use in acetamiprid detection.

Electromagnetic Mechanisms or Chemical Mechanisms? Role of Interfacial Charge Transfer in the Plasmonic Metal/Semiconductor Heterojunction

The plasmonic metal/semiconductor heterojunction provides a unique paradigm for manipulating light to improve the efficiency of plasmonic materials. Previous studies suggest that the improvement originates from the enhanced carrier exchanges between the plasmonic component of the heterojunction and molecules. This viewpoint, known as the chemical mechanism, is reasonable but insufficient, because the construction of the heterojunction will lead to a charge redistribution in the plasmonic component and cause changes in its physical characteristics. Herein, we will try to clarify that these changes are decisive factors in specific applications by investigating the surface-enhanced Raman scattering (SERS) behavior of a typical Ag/TiO₂ heterojunction. We observed significant changes in SERS spectra by modulating the band alignment of the heterojunction in a loop. Identical trends in SERS spectra were observed despite the fact that the charge transfer from the heterojunction to molecules was blocked, suggesting that the major SERS enhancement originates from electromagnetic mechanisms rather than chemical ones.

New Mechanism for Long Photo-Induced Enhanced Raman Spectroscopy in Au Nanoparticles Embedded in TiO2

The photo-induced enhanced Raman spectroscopy (PIERS) effect is a phenomenon taking place when plasmonic nanoparticles deposited on a semiconductor are illuminated by UV light prior to Raman measurement. Results from the literature show that the PIERS effect lasts for about an hour. The proposed mechanism for this effect is the creation of oxygen vacancies in the semiconductor that would create a path for charge transfer between the analyte and the nanoparticles. However, this hypothesis has never been confirmed experimentally. Furthermore, the tested structure of the PIERS substrate has always been composed of plasmonic nanoparticles deposited on top of the semiconductor. Here, gold nanoparticles co-deposited with porous TiO₂ are used as a PIERS substrate. The deposition process confers the nanoparticles a unique position half buried in the nanoporous semiconductor. The resulting PIERS intensity is among the highest measured until now but most importantly the duration of the effect is significantly longer (at least 8 days). Cathodoluminescence measurements on these samples show that two distinct mechanisms are at stake for co-deposited and drop-casted gold nanoparticles. The oxygen vacancies hypothesis tends to be confirmed for the latter, but the narrowing of the depletion zone explains the long PIERS effect.

Si/TiO2/Ag Multistorey Structures with Interfacial Charge Transfer for a Recyclable Surface-Enhanced Raman Scattering Substrate

In this work, highly ordered TiO₂/Ag bilayer structures on p-type silicon (Si) wafers are prepared by photolithography and electrochemical self-assembly methods. The interfacial charge transfer (CT) of this Si/TiO₂/Ag multistorey structure with a specially aligned work function is studied. This is important to deduce the interfacial electron migration behavior of SERS. The three-dimensional finite-difference time-domain (3D FDTD) simulation is used to explore the combined CT-EM enhancement mechanism. The result shows that the electron movement under the CT mechanism can induce the resonance effect of free electrons to further improve EM performance. In addition, the effect of agglomerated Ag nanoparticle size distribution on the SERS property and the self-cleaning property of Si/TiO₂/Ag multistorey structures is investigated. Finally, this unique structure of highly ordered Si/TiO₂/Ag SERS substrate shows superior sensitivity, reproducibility, and stability. Rhodamine 6G (R6G) with trace concentrations as low as 10^-15 M can be detected, and the EF is estimated to be about 8.9 × 10¹³. The relative standard deviation (RSD) at 1511 cm^-1 is about 4.7%. These results are very promising for the practical application of the SERS technique in the rapid trace determination in many fields.

3D hierarchically porous magnetic molybdenum trioxide@gold nanospheres as a nanogap-enhanced Raman scattering biosensor for SARS-CoV-2

The global pandemic of COVID-19 is an example of how quickly a disease-causing virus can take root and threaten our civilization. Nowadays, ultrasensitive and rapid detection of contagious pathogens is in high demand. Here, we present a novel hierarchically porous 3-dimensional magnetic molybdenum trioxide-polydopamine-gold functionalized nanosphere (3D mag-MoO3-PDA@Au NS) composed of plasmonic, semiconductor, and magnetic nanoparticles as a multifunctional nanosculptured hybrid. Based on the synthesized 3D mag-MoO3-PDA@Au NS, a universal "plug and play" biosensor for pathogens is proposed. Specifically, a magnetically-induced nanogap-enhanced Raman scattering (MINERS) detection platform was developed using the 3D nanostructure. Through a magnetic actuation process, the MINERS system overcomes Raman signal stability and reproducibility challenges for the ultrasensitive detection of SARS-CoV-2 spike protein over a wide dynamic range up to a detection limit of 10-15 g mL-1. The proposed MINERS platform will facilitate the broader use of Raman spectroscopy as a powerful analytical detection tool in diverse fields.

Photoactive Control of Surface-Enhanced Raman Scattering with Reduced Graphene Oxide in Gas Atmosphere

Surface-enhanced Raman scattering (SERS) is an ultrahigh sensitive detection technique for a variety of research fields. Both electromagnetic and chemical enhancement mechanisms are generally considered to contribute simultaneously to SERS signals. However, it is difficult to actively control the enhancement of SERS signals after the substrate is fabricated, since tuning one or both of the aforementioned enhancement mechanisms remains an experimental challenge. Here, we propose a method for actively implementing the photoinduced modulation of SERS signals, which is that under UV irradiation, the Fermi level of graphene can be dynamically modulated due to the adsorption and desorption of gas molecules. The method is validated in gas atmospheres of O₂, CO₂, N₂, and air and also demonstrate its generality by different analytes. In addition, the method was successfully applied to the trace detection of pesticides on fruit peels in air environment, which show its practical implications in sensing.

Facile fabrication of PS/Cu2S/Ag sandwich structure as SERS substrate for ultra-sensitive detection

In this work, a serials of PS(polystyrene)/Cu₂S/Ag sandwich substrates were successfully constructed using the magnetic sputtering method by adjusting the Ag sputtering time (0 min, 2 min, 4 min, 6 min, 8 min and 10 min) and used as the surface-enhanced Raman scattering (SERS) substrates. When the Ag sputtering time was 6 min, the strongest SERS signal was observed. The optimized SERS substrate has strong SERS activity on 4-mercaptobenzoic acid (4-MBA), the minimum detection limit was 10^-13 M and the enhancement factor was as high as 4.7 × 10⁷. In addition, the SERS signals were highly reproducible with small standard deviation. The SERS enhancement mechanism of the PS/Cu₂S/Ag system was attributed to the synergistic effect of the chemical mechanism and the electromagnetic enhancement mechanism. This strategy has find a new way for manufacturing SERS activity sensor with high sensitivity and reproducibility.

A recyclable graphene/Ag/TiO2 SERS substrate with high stability and reproducibility for detection of dye molecules

Magnetron sputtering combined with the wet chemical transfer of graphene successfully prepared a multilayer composite material and an efficient photocatalytic renewable SERS substrate. It has excellent photocatalytic activity against dye molecules.

Surface modification and antibacterial properties of superelastic Ti-Zr-based alloys for medical application

To date, significant progress has been achieved in the development of biomedical superelastic Ti-based alloys with high mechanical properties. In view of the high probability of implant-associated infection, an urgent task is to impart bactericidal properties to the material. Herein, advanced superelastic Ti-18Zr-15Nb alloys were surface-etched in a piranha solution, and then Ag nanoparticles were deposited on their surface using a polyol process. This led to the formation of a porous surface layer with a thickness of approximately 100 nm and pore size of less than 20 nm, filled with metallic Ag nanoparticles with an average size of 14 nm. The surface-modified samples showed superior antibacterial activity against E.coli cells. The enhanced bactericidal efficiency is explained by the combination of a higher rate of Ag⁺ ions release and direct contact of E.coli cells with Ag nanoparticles.

The Role of Substrate on Thermal Evolution of Ag/TiO2 Nanogranular Thin Films

In multicomponent thin films, properties and functionalities related to post-deposition annealing treatments, such as thermal stability, optical absorption and surface morphology are typically rationalized, neglecting the role of the substrate. Here, we show the role of the substrate in determining the temperature dependent behaviour of a paradigmatic two-component nanogranular thin film (Ag/TiO2) deposited by gas phase supersonic cluster beam deposition (SCBD) on silica and sapphire. Up to 600 °C, no TiO2 grain growth nor crystallization is observed, likely inhibited by the Zener pinning pressure exerted by the Ag nanoparticles on the TiO2 grain boundaries. Above 600 °C, grain coalescence, formation of However, the two substrates steer the evolution of the film morphology and optical properties in two different directions. anatase and rutile phases and drastic modification of the optical absorption are observed. On silica, Ag is still present as NPs distributed into the TiO2 matrix, while on sapphire, hundreds of nm wide Ag aggregates appear on the film surface. Moreover, the silica-deposited film shows a broad absorption band in the visible range while the sapphire-deposited film becomes almost transparent for wavelengths above 380 nm. We discuss this result in terms of substrate differences in thermal conductivity, thermal expansion coefficient and Ag diffusivity. The study of the substrate role during annealing is possible since SCBD allows the synthesis of the same film independently of the substrate, and suggests new perspectives on the thermodynamics and physical exchanges between thin films and their substrates during heat treatments.

Thermal crowning mechanism in gold-silica nanocomposites: plasmonic-photonic pairing in archetypal two-dimensional structures

A close-packed monolayer of a two-dimensional periodic array of Silica nanospheres (SNs) with gold (Au) crowning, forming a long-ranged archetypal plasmonic-photonic nanocomposite, has been achieved. We investigate the thermal crowning mechanism in such a nanocomposite using electron microscopy and X-ray diffraction techniques. Pre- and post-annealing morphological features reveal gold crowning on top of SNs, at different annealing temperatures for various thicknesses of the sputter-deposited gold. In situ grazing incidence X-ray diffraction was employed to structurally characterize the reconstruction in the Au-layer as a function of the annealing temperature. Finite element methods were used to simulate the interaction between the paired nanocomposites and the incident electromagnetic radiations to elucidate the crowning and nanodrop formation mechanism. This study provides an insight into real-time morphological and structural changes of a dewetting plasmonic film over a photonic basis and explores a robust, reliable, and scalable route to fabricate coupled nanocomposites. Such nanocomposites allow prospective applications in optoelectronics, sensing, catalysis, and surface-enhanced Raman spectroscopy by exploiting the plasmonic-photonic pairing in archetypal two-dimensional structures.

Recent advances and perspectives in photo-induced enhanced Raman spectroscopy

Phototreatment is at the leading edge of a research hot topic as a driving force for structural transformation, spectral and electromagnetism improvements, and the functional performance of nanomaterials. Light irradiation can excite surface plasmons in noble metal nanoparticles, create electron-hole pairs, and produce charge transfer in semiconductor substrates, which have led to it being widely used in surface-enhanced Raman spectroscopy (SERS) for life sciences, environmental protection, and biological analysis. Photo-induced enhanced Raman spectroscopy (PIERS) is a new technology developed on the basis of traditional SERS and has proven to be an efficient way to resolve several critical challenges thanks to its incomparable superiority for incontiguous operation, efficient charge separation and enrichment, and a large signal enhancement for a wide range of biomolecules at the trace level. This makes PIERS a powerful technique with very appealing and promising applications in various branches of analytical science. In this review, the enhancement mechanisms of PIERS are analyzed in comparison with SERS. Afterward, the parameters influencing the enhancement of PIERS, including the substrate, light irradiation, and relaxation are discussed in detail. Finally, some perspectives on further developments of PIERS are exemplified. The PIERS technique will continue to evolve and grow with new developments and its successful application in bioanalysis and life sciences.

Unidirectional/Bidirectional Electron Transfer at the Au/TiO2 Interface Operando Tracked by SERS Spectra from Au and TiO2

Although it is well-known that the size can influence the surface plasmon resonance property of coinage metals and the electronic state of the Mott-Schottky junction formed at the metal/semiconductor interface, insights into how the size can be exploited to optimize the photocatalytic activity and selectivity of metal/semiconductor composites are lacking. Here we utilize operando SERS spectroscopy to identify the size effect on the electron-transfer dynamics and the direction at the Au/TiO₂ interface. This effect was characterized by the photocatalytic reduction sites of p-nitrothiophenol, which were self-tracked with the SERS spectra from Au nanoparticle and inverse-opal structured TiO₂, respectively. The size-dependent unidirectional/bidirectional transfer of photoinduced electrons at the Au/TiO₂ interface was revealed by operando SERS spectroscopy, which enables the rational tuning of the reduction selectivity.

Effect of TiO2 arrays on surface enhanced Raman scattering (SERS) performance for Ag/TiO2 substrates

Ag/TiO₂ nanostructure arrays were constructed on fluorine-doped tin oxide (FTO) via a controllable hydrothermal route and a magnetron sputtering method with a variety of TiO₂ arrays decorated by Ag nanoparticles. Effects of different TiO₂ arrays on the microstructure, composition, and optical properties of the samples were revealed. As surface enhanced Raman scattering (SERS) active substrates, we discussed the sensitivity and reproducibility of Ag/TiO₂ nanostructure arrays for Rhodamine 6G (R6G) molecule detection. It was found that TiO₂ nanosheet (TiO₂(S)) array as a supporting made Ag nanoparticles have a uniform and continuous distribution, which achieved much higher SERS signals. The obtained Ag/TiO₂(S) substrate had an improved enhancement factor of 4.31 × 10⁵ compared with the other Ag/TiO₂ nanostructure arrays of nanorods, nanotubes, and nanotrees. Furthermore, Ag/TiO₂(S) active substrate showed good reproducibility with low relative standard deviation values. Such a remarkable SERS activity could be due to the synergistic effect of electromagnetic enhancement and charge transfer enhancement. Moreover, the TiO₂(S) array with high-exposed {101} facets provided a large adhesion area and generated a strong interaction with external atoms, which would produce high-density 'hot spots' of SERS.

Surface-Enhanced Raman Spectroscopy of Organic Molecules and Living Cells with Gold-Plated Black Silicon

Black silicon (bSi) refers to an etched silicon surface comprising arrays of microcones that effectively suppress reflection from UV to near-infrared (NIR) while simultaneously enhancing the scattering and absorption of light. This makes bSi covered with a nm-thin layer of plasmonic metal, i.e., gold, an attractive substrate material for sensing of bio-macromolecules and living cells using surface-enhanced Raman spectroscopy (SERS). The performed Raman measurements accompanied with finite element numerical simulation and density functional theory analysis revealed that at the 785 nm excitation wavelength, the SERS enhancement factor of the bSi/Au substrate is as high as 10⁸ due to a combination of electromagnetic and chemical mechanisms. This finding makes the SERS-active bSi/Au substrate suitable for detecting trace amounts of organic molecules. We demonstrate the outstanding performance of this substrate by highly sensitive and specific detection of a small organic molecule of 4-mercaptobenzoic acid and living C6 rat glioma cell nucleic acids/proteins/lipids. Specifically, the bSi/Au SERS-active substrate offers a unique opportunity to investigate the living cells' malignant transformation using characteristic protein disulfide Raman bands as a marker. Our findings evidence that bSi/Au provides a pathway to the highly sensitive and selective, scalable, and low-cost substrate for lab-on-a-chip SERS biosensors that can be integrated into silicon-based photonics devices.

A balsam pear-shaped CuO SERS substrate with highly chemical enhancement for pesticide residue detection

Simple and traditional hydrothermal fabrication of a novel balsam pear-shaped CuO with high SERS enhancement is presented. XRD (X-ray diffraction), SEM (scanning electronic microscopy), TEM (transmission electron microscope), HRTEM (high-resolution transmission electron microscope), UV-Vis, and Raman are adopted to ensure that this balsam pear-shaped CuO with dense nanoparticle protuberance is successfully prepared. The LOD of this CuO SERS substrate is 4.79 μg L^-1 with R6G as molecular probe. By using DFT (density functional theory) calculation and FDTD (finite difference time domainmethod) simulation, both EM (electromagnetic enhancement) and CM (chemical enhancement) mechanisms are investigated, and the results show that these two-enhancement mechanisms can coexist in this balsam pear-shaped CuO. Finally, the prepared substrate has been applied for the determination of trace levels of paraquat in solution , and results show that its LOD for paraquat is 275 μg L^-1 (optimum Raman band: 1646 cm^-1 Raman shift), which is better than the government standard in China. A dexterous and facile way for fabrication of CuO SERS-active substrates with low cost and high performance, quite promising in detection of chemically hazardous substances and pesticide residue is provided. Graphical abstract.

Irreversible accumulated SERS behavior of the molecule-linked silver and silver-doped titanium dioxide hybrid system

In recent years, surface-enhanced Raman scattering (SERS) of a molecule/metal–semiconductor hybrid system has attracted considerable interest and regarded as the synergetic contribution of the electromagnetic and chemical enhancements from the incorporation of noble metal into semiconductor nanomaterials. However, the underlying mechanism is still to be revealed in detail. Herein, we report an irreversible accumulated SERS behavior induced by near-infrared (NIR) light irradiating on a 4-mercaptobenzoic acid linked with silver and silver-doped titanium dioxide (4MBA/Ag/Ag-doped TiO₂) hybrid system. With increasing irradiation time, the SERS intensity of 4MBA shows an irreversible exponential increase, and the Raman signal of the Ag/Ag-doped TiO₂ substrate displays an exponential decrease. A microscopic understanding of the time-dependent SERS behavior is derived based on the microanalysis of the Ag/Ag-doped TiO₂ nanostructure and the molecular dynamics, which is attributed to three factors: (1) higher crystallinity of Ag/Ag-doped TiO₂ substrate; (2) photo-induced charge transfer; (3) charge-induced molecular reorientation.

The authors report that near-infrared light induces an irreversible accumulated Surface-enhanced Raman scattering (SERS) behavior of a molecule/metal–semiconductor hybrid system. They investigate the underlying mechanism and show that it is attributed to crystallinity, charge transfer and reorientation.

Retracted Article: Synergistic action of star-shaped Au/Ag nanoparticles decorated on AgFeO2 for ultrasensitive SERS detection of a chemical warfare agent on real samples

It is a great challenge to design and fabricate a cost-effective surface-enhanced Raman spectroscopy (SERS) substrate with excellent reproducibility and sensitivity for reliable environmental analysis. In this work, we have synthesized silver ferrite (AgFeO₂) interlinked with star-shaped gold/silver (Au/Ag) bimetallic (BM) nanoparticles (NPs) by a simple physical method for the effective detection of an acetylcholinesterase (AchE) inhibitor, paraoxon ethyl (PE). The successful construction of AgFeO₂@Au/Ag NPs was confirmed by UV-Vis spectroscopy, X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. The enhancement of the SERS signal is achieved by the synergistic effect of the charge transfer mechanism and electromagnetic mechanism. The Raman peak centered at 1357 cm^-1 was selected as an ideal peak for the quantitative analysis of PE. The AgFeO₂@Au/Ag NPs can detect PE down to 1 × 10^-8 M with a high analytical enhancement factor of 3.53 × 10⁶ and excellent uniformity, as determined randomly from 14 spots (relative standard deviation, RSD, <15%). The recovery values of PE in tap water and tomato juice were from 93.16% to 99.16%. All these results suggest that our proposed SERS substrate has promising potential for the detection of PE. The proposed simple strategy for PE detection by SERS using AgFeO₂@Au/Ag NPs paves the way for future reliable environmental analysis and real sample monitoring.

Detection of several quinolone antibiotic residues in water based on Ag-TiO2 SERS strategy

Herein, a surface-enhanced Raman scattering (SERS) strategy based on semiconducting substrate was exploited for detection of several antibiotic residues both in ultrapure water system and in actual water system. The as-prepared Ag-TiO₂ (Ag synchronously deposited and doped TiO₂) nanoparticle SERS-active substrate can achieve high sensitive SERS detection for difloxacin hydrochloride, ciprofloxacin, enrofloxacin, danofloxacin and enoxacin (five widely used quinolone antibiotics) in actual water samples, and the detection limits are as low as 4.36 × 10^-12, 7.08 × 10^-11, 3.94 × 10^-11, 3.16 × 10^-11 and 3.15 × 10^-10 mol/L, respectively. These detection limits are far below the maximum of residue limit (3.01 × 10^-7 mol/L) stipulated by the European Union. And, the desirable quantitative relationships can be obtained in a wide concentration range. The recoveries of five antibiotic residues from spiked actual water samples are found to be more than 80.8% with the relative standard deviations between 2.1% and 4.7%. Even, the proposed SERS method can accurately distinguish every antibiotic species from a mixed antibiotic residue sample with multiple antibiotics. And, Ag-TiO₂ nanoparticles can also serve as an efficient photocatalyst for photocatalytic degradation of these antibiotic residues, which provides a multi-functional platform for synchronous determination and degradation of antibiotic residues in real environment.

Surface-enhanced Raman scattering studies of Cu/Cu2O Core-shell NPs obtained by laser ablation

In order to perform SERS (surface-enhanced Raman scattering) measurements, spherical Cu/Cu₂O core-shell NPs with a rather rough rugged surface and well-defined crystallographic structures were fabricated using nanosecond Ce: Nd YAG pulsed laser ablation in liquid (PLAL). Raman, Fourier transform infrared (FTIR) spectroscopy and TEM imaging of the prepared NPs reveal the existence of additional minority CuO phase, not determined earlier through XRD patterns. The SERS activity of Cu/Cu₂O core-shell NPs substrates was investigated by using crystal violet (CV) and methylene blue (MB) as the analyte molecules under 532 nm excitation wavelength irradiation. The effect of localized surface plasmon resonance (LSPR) from Cu core contributing to the electromagnetic enhancement and Cu2O shell with a rough surface which itself contributes to chemical enhancement with adsorbed analyte molecule is due to a high overall SERS enhancement. The intensities of the totally and non-totally symmetric modes were used to calculate the degree of charge-transfer. The results demonstrate that the LSPR enhancement dominates charge-transfer resonance contribution in SERS of Cu/Cu2O-CV and Cu/Cu2O -MB systems. The reproducibility of the prepared SERS substrates was investigated and the SERS signals intensity variation was <28%.

Pressure-induced SERS enhancement in a MoS2/Au/R6G system by a two-step charge transfer process

Pressure-induced surface-enhanced Raman spectroscopy (PI-SERS) represents a new frontier in the research field of SERS. However, relatively few studies have focused on PI-SERS due to many difficulties, such as easy aggregation of nanoparticles, and difficulty in understanding the interaction mechanisms between probe molecules and the SERS substrate at high pressure. Here we developed an efficient semiconductor-metal SERS substrate (MoS₂/Au) to study PI-SERS. Different from the previously reported monotonous decrease in Raman intensities upon compression, an anomalous Raman enhancement of R6G molecules adsorbed on the MoS₂/Au substrate was observed up to 2.39 GPa, at which the degree of charge transfer (ρ_CT) between the R6G molecules and the MoS₂/Au substrate reaches a maximum. By comparison, it is proposed that the decoration of Au on the SERS system could bring about a two-step charge transfer (CT) process, introduce localized surface plasmon resonance (LSPR), and thus favor the PI-SERS enhancement. Moreover, this charge transfer also causes obvious changes in the optical behaviors of R6G molecules upon compression. This brings new insights into the SERS study and also offers new ideas for the development of SERS application in high pressure studies.

Synergistic Enhancement Effect for Boosting Raman Detection Sensitivity of Antibiotics

In this paper, a two-step method is used to prepare a regenerative three-dimensional (3D) ZnO/Ag@Au substrate for developing a superior sensitive surface enhanced Raman scattering (SERS) method for detecting antibiotics. A great electromagnetic enhancement is observed from the as-prepared composite substrate, which is triggered by tuning the electron distribution of metals and semiconductor metal oxide. The strong interaction between target sample and the huge surface area of ZnO/Ag@Au composite promotes the charge transfer to produce promising chemical enhancement. The synergistic physical and chemical enhancement mechanisms are validated by density functional theory and finite difference time domain simulation. Additionally, the presence of light "echo effect" in the 3D structure of ZnO support could also amplify the efficiency of light excitation for Raman scattering. The above-stated merits benefit to boost the Raman scattering detection sensitivity for real samples. The ZnO/Ag@Au-based SERS substrate could detect rhodamine 6G molecules with an enhancement factor of up to 1.48 × 10⁹ and the lowest detectable concentration of 10^-10 M. As a real application, antibiotics sulfapyridine in milk is determined by using the proposed SERS protocol, and the limit of detection at 1 × 10^-9 M could be reached. As a prospective, the ZnO/Ag@Au-based SERS method would be extended for food safety and biomedicine analysis.

Plasmonic Ag decorated CdMoO4 as an efficient photocatalyst for solar hydrogen production

The synthesis of Ag-nanoparticle-decorated CdMoO₄ and its photocatalytic activity towards hydrogen generation under sunlight has been demonstrated. The CdMoO₄ samples were synthesized by a simple hydrothermal approach in which Ag nanoparticles were in situ decorated on the surface of CdMoO₄. A morphological study showed that 5 nm spherical Ag nanoparticles were homogeneously distributed on the surface of CdMoO₄ particles. The UV/DRS spectra show that the band gap of CdMoO₄ was narrowed by the incorporation of a small amount of Ag nanoparticles. The surface plasmonic effect of Ag shows broad absorption in the visible region. The enhanced photocatalytic hydrogen production activities of all the samples were evaluated by using methanol as a sacrificial reagent in water under natural sunlight conditions. The results suggest that the rate of photocatalytic hydrogen production using CdMoO₄ can be significantly improved by loading 2% Ag nanoparticles: i.e. 2465 μmol h⁻¹ g⁻¹ for a 15 mg catalyst. The strong excitation of surface plasmon resonance (SPR) absorption by the Ag nanoparticles was found in the Ag-loaded samples. In this system, the role of Ag nanoparticles on the surface of CdMoO₄ has been discussed. In particular, the SPR effect is responsible for higher hydrogen evolution under natural sunlight because of broad absorption in the visible region. The current study could provide new insights for designing metal/semiconductor interface systems to harvest solar light for solar fuel generation.

Plasmonic enhancement of photocatalytic hydrogen generation is demonstrated using hierarchical Ag decorated CdMoO₄ synthesized using a hydrothermal method.

SERS study of Ag/FeS/4-MBA interface based on the SPR effect

In this work, an ordered metal-semiconductor molecular system was introduced, and 4-mercaptobenzoic acid (4-MBA) was employed to study the charge transfer (CT) at the metal-semiconductor interface based on surface-enhanced Raman scattering (SERS) spectra. The thickness of the sputtered FeS was controlled so that the surface plasmon resonance (SPR) of Ag underwent a displacement change, and the contribution of the SPR to the CT was studied through surface plasmon (SP) absorption. Furthermore, SERS spectra obtained at different excitation wavelengths were used to calculate the degree of CT in the layer-by-layer sputtering system. When Ag was irradiated with incident light, the strong SPR of Ag was excited, generating an increased electromagnetic field (EM). This amplified EM generated hot electrons at the interface between the FeS and Ag, and then the hot electrons were rearranged. Therefore, we established a simple and effective method for studying the impact of SPR on interfacial CT and analyzed the SERS spectra in accordance with Lombardi's basic theory and the physical effects associated with SPR. This theory is in good agreement with the experimental results. On this basis, we also proposed a mechanism by which SPR impacts the CT, which is beneficial for studying interfacial CT and obtaining an in-depth understanding of the CT mechanism in SERS. This work also enables the expansion of the applications of the SERS technique in the field of nanomaterials.

Single sea urchin-MoO3 nanostructure for surface enhanced Raman spectroscopy of dyes

Enhancing the surface-enhanced Raman scattering (SERS) activity of semiconductor metal oxide nanostructures by controlling the morphology and oxygen vacancies towards trace detection of organics is of significant interest. In this study, MoO₃ with a novel sea urchin morphology is synthesized employing chemical bath deposition and consists of hundreds of ∼15 μm long spikes originating from the core forming 20-40 micron globular structures. The spikes taper to form 20 nm sharp tips. SERS of rhodamine 6G (R6G) over MoO₃ sea urchins has been investigated and compared to that of 1D h-MoO₃ nanorod arrays. The SERS activity is morphology dependent and the sea urchin-like morphology exhibits higher SERS activity with an enhancement factor (EF) of the order 10⁵ and a detection limit of 100 nM, while for h-MoO₃ nanorods, the corresponding values are 10³ and 1 μM, respectively. X-ray photoelectron spectroscopy reveals a high concentration of Mo⁺⁵ states in sea urchins indicating lattice oxygen vacancies. The observed EF is quite high for a metal oxide substrate and is attributed to the enhanced charge transfer between analyte molecules and the substrate promoted by the oxygen vacancies along with surface defects and hydroxyl groups on MoO₃ sea urchins providing more active sites for the adsorption of probe molecules. The role of oxygen vacancies is confirmed by the lower EF value exhibited by the stoichiometric 1D h-MoO₃. Raman mapping of a single sea urchin is achieved with good R6G intensity and indicates that the tips of spiky features are involved in SERS enhancement. The reusability of substrates is shown for repeated cycles of R6G adsorption by UV irradiation exploiting the photocatalytic activity of MoO₃ nanostructures.

Role of TiO2 Nanoparticles and UV Irradiation in the Enhancement of SERS Spectra To Improve Levamisole and Cocaine Detection on Au Substrates

The original goal of this study was the employment of surface-enhanced Raman spectroscopy (SERS) for the analysis of real cocaine samples (containing adulterants) on composite Au-TiO₂ nanomaterials to achieve low detection limits suitable for the analysis of illicit drugs and controlled substances and to exploit the photodegradation activity of TiO₂ to recycle the SERS substrate for repeated analyses. The photodegradation (self-cleaning) effects of the Au-TiO₂ composite nanomaterials by ultraviolet (UV) radiation are known. These effects were investigated on large-area SERS substrates immersed in the TiO₂ nanoparticle aqueous suspension. The cocaine samples were measured on electrochemically gold-plated platinum targets. Surprisingly, the intensity of SERS spectra of the pure cocaine did not change after immersion in a suspension of TiO₂ under UV irradiation. However, for some real cocaine samples, the overall intensity of the SERS spectra was even higher after the treatment by TiO₂ and UV radiation as compared to the usual Au substrate. This unexpected signal amplification (valuable for illicit drug detection) was found to be caused mainly by the contained levamisole, which is used as a medical drug and is one of the frequent adulterants of cocaine. Both the sole effect of TiO₂ on the levamisole spectrum intensity and the role of UV irradiation were inspected separately. Finally, an investigation of both the TiO₂ and UV radiation treatments was performed, demonstrating (i) the necessity of both factors for selective SERS signal enhancement of the adulterant and (ii) the revision of general anticipation of the role of TiO₂ in SERS systems.

A green and general strategy for the synthesis of hollow Ag/CdS nanocomposites for superior SERS performance

In this study, we developed a convenient, environmentally friendly approach for the fabrication of hollow Ag/CdS composites, which presented superior SERS performance.

Surface-enhanced Raman scattering (SERS) as a probe for detection of charge-transfer between TiO2 and CdS nanoparticles

The differences of charge transfer processes in different assemblies were observed by the optical method of SERS.

Plasmonic 3D Semiconductor-Metal Nanopore Arrays for Reliable Surface-Enhanced Raman Scattering Detection and In-Site Catalytic Reaction Monitoring

It is urgent to develop a rapid, reliable, and in-site determination method to detect or monitor trace amounts of toxic substances in the field. Here, we report an alternative surface-enhanced Raman scattering (SERS) method coupled with a portable Raman device on a plasmonic three-dimension (3D) hot spot sensing surface. Plasmonic Ag nanoparticles (AgNPs) were uniformly deposited on 3D TiO₂ nanopore arrays as a sensitive SERS substrate, and further coated with graphene oxide (GO). We demonstrate the plasmon-induced SERS enhancement (5.8-fold) and the improvement of catalytic activity by incorporation of plasmonic AgNPs into the 3D TiO₂ nanopore arrays. The modification of GO on the TiO₂-Ag nanopore array further increases by a 6.2-fold Raman enhancement compared to TiO₂-Ag while maintaining good uniformity (RSD < 10%). The optimized TiO₂-Ag-GO substrate shows powerful quantitative detection potential for drug residues in fish scales via a simple scrubbing method, and the limit of detection (LOD) for crystal violet (CV) was 10^-8 M. The SERS substrate also showed detection practicability of pesticide residues in banana peel with an LOD of 10^-7 M. In addition, our TiO₂-Ag-GO substrate exhibits excellent SERS self-monitoring performance for catalytic reduction of multiple organics in NaBH₄ solution, and the substrate shows good recyclability of 6 cycles. Such a 3D TiO₂-Ag-GO substrate is a promising SERS substrate with good sensitivity, uniformity, and reusability, and may be utilized for further miniaturization for point of analytical applications.

Self-Assembled Ag-Cu₂O Nanocomposite Films at Air-Liquid Interfaces for Surface-Enhanced Raman Scattering and Electrochemical Detection of H₂O₂

We employ a facile and novel route to synthesize multifunctional Ag-Cu₂O nanocomposite films through the self-assembly of nanoparticles at an air-liquid interface. In the ethanol-water phase, AgNO₃ and Cu(NO₃)₂ were reduced to Ag-Cu₂O nanoparticles by NaBH₄ in the presence of cinnamic acid. The Ag-Cu₂O nanoparticles were immediately trapped at the air-liquid interface to form two-dimensional nanocomposite films after the reduction reaction was finished. The morphology of the nanocomposite films could be controlled by the systematic regulation of experimental parameters. It was found that the prepared nanocomposite films serving as the substrates exhibited strong surface-enhanced Raman scattering (SERS) activity. 4-aminothiophenol (4-ATP) molecules were used as the test probes to examine the SERS sensitivity of the nanocomposite films. Moreover, the nanocomposite films synthesized by our method showed enhanced electrocatalytic activity towards hydrogen peroxide (H₂O₂) and therefore could be utilized to fabricate a non-enzymatic electrochemical H₂O₂ sensor.

Synergistic Bacterial Stress Results from Exposure to Nano-Ag and Nano-TiO2 Mixtures under Light in Environmental Media

Due to their widespread use and subsequent release, engineered nanomaterials (ENMs) will create complex mixtures and emergent systems in the natural environment where their chemical interactions may cause toxic stress to microorganisms. We previously showed that under dark conditions n-TiO₂ attenuated bacterial stress caused by low concentrations of n-Ag (<20 μg L^-1) due to Ag⁺ adsorption, yet, since both n-Ag and n-TiO₂ are photoactive, their photochemistries may play a key role in their interactions. In this work, we study the chemical interactions of n-Ag and n-TiO₂ mixtures in a natural aqueous medium under simulated solar irradiation to investigate photoinduced stress. Using ATP levels and cell membrane integrity as probes, we observe that n-Ag and n-TiO₂ together exert synergistic toxic stress in Escherichia coli. We find increased production of hydrogen peroxide by the n-Ag/n-TiO₂ mixture, revealing that the enhanced photocatalytic activity and production of ROS likely contribute to the stress response observed. Based on STEM-EDS evidence, we propose that a new composite Ag/TiO₂ nanomaterial forms under these conditions and explains the synergistic effects of the ENM mixture. Overall, this work reveals that environmental transformations of ENM mixtures under irradiation can enhance biological stress beyond that of individual components.

Photo-induced surface-enhanced Raman spectroscopy from a diphenylalanine peptide nanotube-metal nanoparticle template

UV irradiation of aligned diphenylalanine peptide nanotubes (FF-PNTs) decorated with plasmonic silver nanoparticles (Ag NPs) enables photo-induced surface-enhanced Raman spectroscopy. UV-induced charge transfer facilitates a chemical enhancement that provides up to a 10-fold increase in surface-enhanced Raman intensity and allows the detection of a wide range of small molecules and low Raman cross-section molecules at concentrations as low as 10-13 M. The aligned FF-PNT/Ag NP template further prevents photodegradation of the molecules under investigation. Our results demonstrate that FF-PNTs can be used as an alternative material to semiconductors such as titanium dioxide for photo-induced surface-enhanced Raman spectroscopy applications.

High photodegradation and antibacterial activity of BN–Ag/TiO2 composite nanofibers under visible light

To develop material with good photocatalytic properties for organic compound degradation and bacterial removal, we produced Ag/TiO₂ and BN–Ag/TiO₂ composite nanofibers that included controlled amounts of boron nitride (BN) nanosheets and silver (Ag).

Ag Nanoparticles Located on Three-Dimensional Pine Tree-Like Hierarchical TiO2 Nanotube Array Films as High-Efficiency Plasmonic Photocatalysts

High specific surface area three-dimensional pine tree-like hierarchical TiO2 nanotube array films loaded with Ag nanoparticles were successfully prepared by one-step hydrothermal reaction combining with simple and feasible magnetron sputtering. The composite Ag/TiO2-branched nanotube arrays show outstanding photocatalytic property, which is attributed to the boost of plasmonic enhancement carrier generation and separation, higher specific surface area, higher organic pollutant absorption, faster charge transport, and superior light-harvesting efficiency for efficient charge collection. The work provides a cost-effective and flexible pathway to develop high-performance photocatalyst or optoelectronic devices.

Dual Functional Ta-Doped Electrospun TiO2 Nanofibers with Enhanced Photocatalysis and SERS Detection for Organic Compounds

There is a growing interest in multifunctional nanomaterials for the detection as well as degradation of organic contaminants in the water. In this work, we report on the development of dual functional TiO₂ nanofibers (TNF) with different tantalum (Ta) doping (1-10 mol %) by a simple electrospinning technique. As-prepared TNF show mesoporous dominant structure, which are favorable for photocatalytic activity due to the presence of catalytic spots. Ta doping decreases the crystalline size within TiO₂ matrix because of the incorporation of Ta⁵⁺ ions and restricts the phase transformation from anatase to rutile. Ta doping slightly enhances the visible light absorption because of the Ti³⁺ defects sites created upon Ta⁵⁺ doping. The effect of Ta doping within TiO₂ matrix was systematically studied for the degradation of methylene blue (MB) dye under ultraviolet (UV) and solar light irradiation. The 5% Ta-doped TNF were found to be optimal and showed 5.1 and 2.2 times higher photocatalytic activity as compared to TNF under UV and solar light irradiation, respectively. The effect of Ta doping for the detection of MB molecules was also studied by surface enhanced Raman scattering (SERS). It was observed that 5% Ta-doped TNF exhibit higher photocatalytic activity and enhanced SERS signals of adsorbed MB molecules as compared to the TNF. The enhanced photocatalytic and SERS activities can be explained as combined effects of enhanced visible light absorption, lower crystalline size, and slightly higher surface area. The observed results show that Ta doping induces new energy levels below the conduction band of TiO₂ because of Ti³⁺ defects, which inhibit the photogenerated charge recombination acting as electron traps and promote charge transfer mechanism acting as an intermediate state for TiO₂ to MB molecule electron transfer, and are mainly responsible for the enhanced photocatalytic and SERS activities, respectively.

The effect of nano-TiO2 photocatalysis on the antioxidant activities of Cu, Zn-SOD at physiological pH

Security issues of nanoparticles on biological toxicity and potential environmental risk have attracted more and more attention with the rapid development and wide applications of nanotechnology. In this work, we explored the effect and probable mechanism of nano-TiO₂ on antioxidant activity of copper, zinc superoxide dismutase (Cu, Zn-SOD) under natural light and mixed light at physiological pH. Nano-TiO₂ was prepared by sol-hydrothermal method, and then characterized by X-ray Diffraction (XRD) and Transmission electron micrographs (TEM). The Cu, Zn-SOD was purified by sephadex G75 chromatography and qualitatively analyzed by sodium dodecyl sulfate polypropylene amide gel electrophoresis (SDS-PAGE). The effect and mechanism were elucidated base on Fourier Transform Infrared Spectrometer (FT-IR), Circular Dichroism (CD), zeta potential, and electron spin resonance (ESR) methods. Accompanying the results of FT-IR, CD and zeta potential, it could be concluded that nano-TiO₂ had no effect on the antioxidant activity of Cu, Zn-SOD by comparing the relative activity under natural light at physiological pH. But the relative activity of Cu, Zn-SOD significantly decreased along with the increase of nano-TiO₂ concentration under the mixed light. The results of ESR showed the cause of this phenomenon was the Cu(II) in the active site of Cu, Zn-SOD was reduced to Cu(I) by H₂O₂ and decreased the content of active Cu, Zn-SOD. The reduction can be inhibited by catalase. Excess O₂^·- produced by nano-TiO₂ photocatalysis under mixed light accumulated a mass of H₂O₂ through disproportionation reaction in this experimental condition. The results show that nano-TiO₂ cannot affect the antioxidant activity of Cu, Zn-SOD in daily life. The study on the effect of nano-TiO₂ on Cu, Zn-SOD will provide a valid theory support for biological safety and the toxicological effect mechanism of nanomaterials on enzyme.