Raman Signal Of Rhodamine 6G Research Articles

Silver nanoparticles modified on cicada wings affect fluorescence and Raman signals based on electromagnetic and chemical enhancement mechanisms

The electromagnetic enhancement (EM) mechanism is one of the important theories that need to be mastered to study surface-enhanced fluorescence (SEF) and surface-enhanced Raman scattering (SERS). However, the charge transfer in the chemical enhancement (CM) mechanism has different effects on the two. The study developed a simple and environmentally friendly composite structural substrate by depositing silver (Ag) on the rough surface with regular columnar protuberances of bio-material cicada wings (CW) using magnetron sputtering technology. The formation of Ag nano-islands enhanced the fluorescence and Raman signals of rhodamine 6G (R6G), while the addition of silver nanoparticles (AgNPs) quenched the fluorescence. To explore the magical phenomenon, the electromagnetic field distribution on the surface of the substrate was simulated through three-dimensional finite difference time domain (3D-FDTD), which verified the experimental results of SEF and SERS. The results calculated by Gaussian16 with Density Functional Theory (DFT) and time-dependent density functional theory (TDDFT) explained the effect of adding AgNPs on the surface of the substrate on the fluorescence intensity. The work not only contributes experimental data and theoretical results to the EM mechanism and CM mechanism in enhanced spectra, but also provides ideas for preparing new SEF and SERS substrates.

Lotus leaf-inspired biomimetic SERS substrate for detection of thiram on apple

Lotus leaf is a super-hydrophobic material found in nature. Drawing inspiration from the micro-nano structure of lotus leaf surface, a hybrid surface-enhanced Raman spectroscopy (SERS) substrate owning both hydrophobic and hydrophilic properties was developed. The biomimetic part, which was fabricated by replicating the surface structure of lotus leaf using polydimethylsiloxane, exhibited a hydrophobic surface with a contact angle of 150.3°. Meanwhile, silver nanoparticles-coated filter paper was assembled on the top of the biomimetic part to render hydrophilic regions for SERS detection. Silver nanoparticles on the surface of filter paper owned a size of approximately 70–80 nm with an interval of about 5–10 nm. The hydrophobic/hydrophobic hybrid regions on the substrate significantly enhanced Raman signals of rhodamine 6g with mitigated coffee ring effects, showing a limit of detection low to 10−10 M. Notably, the limit of detection of this technique for thiram on apple surface reached 0.5 ng/cm2, which was lower than the reported methods. The prepared substrate displayed exceptional uniformity and stability, with an RSD value of 7.21% calculated based upon 30 randomly selected Raman signals, and experienced a decrease in signal by only 29.7% after 30-d storage. This biomimetic substrate can be utilized for batch detection of pesticide residues on fresh produce with high sensitivity, thereby owning great potential for application as a rapid detection tool for food safety.

Surface-enhanced Raman scattering of graphene oxide chemically modified by perylene diimide

A soluble perylene diimide derivative are bonded to graphene oxide via esterification, which is applied as the flexible surface-enhanced Raman scattering active substrate for detecting rhodamine 6G. The esterification destroys the crystalline structure of graphene oxide and causes graphitization to some extent. The efficient charge transfer processes from rhodamine 6G and perylene diimide to graphene oxide result in the weak emissions and reduce the background signals. The enhanced Raman signals of rhodamine 6 G on graphene oxide-perylene diimide is increased nearly four times that on graphene oxide without modification. The analysis of the optical spectra and energy levels of the compounds indicates that the multiple charge transfer processes contribute to the enhanced Raman signals of rhodamine 6G on graphene oxide-perylene diimide.

A highly reliable, integration-time and laser-power independent, self-referenced SERS sensor with an extended dynamic range for the detection of melamine in milk

An ultrasensitive nanosculptured thin film (nSTF) based self-referenced SERS sensing platform for the detection of melamine in milk samples is developed. The self-referenced SERS platform consists of a monolayer of 4-aminothiophenol (4-ATP), sandwiched between Ag nSTF and Ag nanoislands (NIs), deposited over a Si substrate. The SERS signal from the sandwiched 4-ATP monolayer acts as a self-referenced signal. The self-referenced platform offers the advantage of independence of Raman signal on the laser power, integration time of the detector of the spectrometer, or ambient conditions. The dynamic range of the sensor, mostly limited by the limits on laser power and integration time of spectrometer, can now be extended due to the independence of the sensor from these two parameters. A significant enhancement in the Raman signal of rhodamine 6G of the order of 1013 is achieved for the SERS active substrate. The self-referenced SERS sensor offers a linear response over the extended dynamic range from 0.001 to 10 ppm for melamine in spiked milk samples. The achieved limit of detection for melamine in spiked milk samples is 1 ppb. The self-referenced sensor will be of great value for real-time detection of melamine in milk samples, and food safety.

Gold nanohole arrays with ring-shaped silver nanoparticles for highly efficient plasmon-enhanced fluorescence

To enhance the interaction between electromagnetic fields and reduce photoluminescence (PL) lifetime in plasmon-enhanced fluorescence, this study presents a novel approach involving the fabrication of gold (Au) nanohole arrays (ANA) decorated with ring-shaped silver nanoparticles (AgNPs) on a silicon-dioxide (SiO2)/silver (Ag) substrate. The surface plasmon resonance coupling in terms of the PL reactions of ANA substrates with and without ring-shaped AgNPs is investigated via experiments and numerical simulations. The remarkable enhancement of PL intensity of the proposed substrate is attributed to increased absorption, which enables the tuning of surface-enhanced electromagnetic fields. Specifically, the Raman signal of rhodamine 6G (R6G) dye and the PL intensity of 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) molecules are significantly enhanced 3.7 and 2.2 times, respectively, compared to those of the bare ANA substrate. Meanwhile, the PL lifetime is reduced by 46.15%. These results confirm that ANAs decorated with ring-shaped AgNPs can significantly improve plasmon-enhanced fluorescence. The findings presented herein demonstrate the potential to revolutionize biosensing, imaging, and photonics.

Band Alignment Enabling Effective Charge Transfer for the Highly Enhanced Raman Scattering and Fluorescence of Metal-Nanoparticle-Decorated Conjugated Polymer Nanowires.

The charge transfer (CT) process has attracted much attention due to its contribution to the improvement of spectroscopic phenomena such as Raman scattering and fluorescence. A current challenge is understanding what factors can influence CT. Here, it is demonstrated that the enhancement factor (EF) of CT (∼2000) can reach the level of electromagnetic enhancement (∼1680) when resonant CT is carried out by (Fermi level energy) band alignment between a metal nanoparticle (NP) and conjugated polymer (polypyrrole (PPy)) nanowire (NW). This band alignment results in an on- or off-resonant CT. As a proof of concept for CT based surface enhanced Raman scattering (SERS) template, the Ag NPs-decorated PPy NW is utilized to effectively enhance the Raman signal of rhodamine 6G (EF of 5.7 × 105). Hence, by means of our demonstration, it is proposed that controlling the band alignment should be considered an important parameter for obtaining a large EF of spectroscopic phenomena.

Porous silicon decorated with Au/TiO2 nanocomposites for efficient photoinduced enhanced Raman spectroscopy.

In this study, we investigated the potential of porous silicon (PSi) modified with Au/TiO2 nanocomposites (NCPs) as a substrate for photoinduced enhanced Raman spectroscopy (PIERS). One-step pulsed laser-induced photolysis (PLIP) was used to embed Au/TiO2 NCPs in the surface of PSi. Scanning electron microscopy revealed that adding TiO2 nanoparticles (NPs) during PLIP led to the formation of predominantly spherical Au NPs with a diameter of approximately 20 nm. Furthermore, modifying the PSi substrate with Au/TiO2 NCPs considerably enhanced the Raman signal of rhodamine 6G (R6G) after 4 h of ultraviolet (UV) irradiation. Real-time monitoring of the Raman signals of R6G at different concentrations under UV irradiation revealed that the amplitude of the signals increased with the irradiation time for R6G concentrations ranging from 10-3 M to 10-5 M. PSi substrates decorated with Au/TiO2 NCPs may be used to develop materials for PIERS applications.

Nanogold-capped poly(DEGDMA) microparticles as surface-enhanced Raman scattering substrates for DNA detection

A novel platform for surface-enhanced Raman scattering (SERS) was fabricated consisting of diethylene glycol dimethacrylate microparticles prepared by gamma-radiation initiated polymerization and decorated with gold nanoparticles. The comparison of bare and decorated microparticles shows significant SERS enhancement in the Raman signal of rhodamine 6G on the latter. For 532, 633 and 785 nm excitations the near-infrared one was found to show the highest enhancement on the substrate, which also showed excellent temporal stability and spatial uniformity. The practical application potential of the SERS substrate is demonstrated with the detection of deoxyribonucleic acid sequences.

Fabrication of low cost highly structured silver capped aluminium nanorods as SERS substrate for the detection of biological pathogens

We report the fabrication of low cost highly structured silver (Ag) capped aluminium (Al) nanorods (NRs) as surface enhanced Raman spectroscopy (SERS) substrate utilising the glancing angle deposition technique. The nano-capping of silver onto the Al NRs can concentrate the local electric field within the minimal volume that can serve as hotspots. The average size of the Ag nanocaps was 50 nm. The newly proposed nanoporous Ag capped Al NRs as SERS substrate could detect the Raman signal of rhodamine 6G (R6G) up to 10−15 molar concentration. The significant enhancement in the Raman signal of 107 was achieved for Ag capped Al NRs considering R6G as a probe molecule. Using the developed SERS substrate, we recorded Raman spectra for Escherichia coli bacteria with its concentration varying from 108 colony forming units per ml (CFU ml−1) up to 102 CFU ml−1. All the reported Raman spectra were acquired by a portable handheld Raman spectrometer. Hence, this newly proposed low cost, effective SERS substrate can be used commercially for the onsite detection of clinical pathogens. The 3D finite difference time domain simulation model was performed for Ag capped Al nanostructure to understand the generation of hotspots. The simulated results show excellent agreement with the experimental results. We fabricated uncapped Ag nanorods of similar dimensions and performed the experimental measurements and simulations for comparison. We found a significant enhancement in Ag capped Al NRs compared to the long Ag NRs. The description of the Raman signal enhancement has been elaborated.

Gold nanoworms: Optical properties and simultaneous SERS and fluorescence enhancement.

Fabrication of platforms for efficient Raman and fluorescence enhancement is very attractive for plasmon-based molecular sensing. For superior sensitivity, the plasmonic constituents of such platforms should be effective electromagnetic field enhancers. Furthermore, nanoparticles having plasmon peak in the spectral range of therapeutic window are superior for biomedical application. Herein, we show that worm-shaped Au nanoparticles can be used for simultaneous surface enhanced Raman scattering (SERS) and metal enhanced fluorescence (MEF). Gold nanoworms (Au-NWs) with an intense plasmon absorption in the therapeutic window were synthesized using a facile single-stepped recipe. Electron microscopy imaging revealed that Au-NWs have a non-uniform surface. Owing to their special morphology, three distinct plasmon bands were seen in the experimental spectrum. The presence of three plasmon peaks was also verified by finite element based simulations. The simulation results further show that Au-NWs can provide intense near field enhancement for multiple excitation wavelengths. As a proof of concept, we have used Au-NWs based platforms for simultaneous enhancement of fluorescence and Raman signal of rhodamine 6G (R6G) dye molecule.

Plasmon-exciton coupling by hybrids between graphene and gold nanorods vertical array for sensor

The graphene/gold nanorods vertical array (G/GNRs-VA) hybrid substrate was fabricated by self-assembly and wet-etching method, which demonstrated high performance in surface-enhanced Raman scattering (SERS). By combining the excellent electromagnetic (EM) enhancement of the GNRs-VA and the distinctive physical/chemical properties of graphene, the G/GNRs-VA hybrid substrate has high sensitivity, which can detect Raman signal of Rhodamine 6G (Rh6G) at concentrations as low as 10−13M. This phenomenon can be easily reproduced in our experiment. Among these randomly selected points, we calculated the relative standard deviations (RSD) at 1360cm−1 and 1650cm−1, and got the results as7.2% and 7.3%, respectively. Compared with GNRs-VA, hybrid substrates exhibit stronger Raman signal, which is mainly attributed to chemical enhancement (CM) of graphene. COMSOL software was used to simulate local electromagnetic field of the SERS substrate, which is consistent with experimental result. Moreover, G/GNRs-VA hybrid substrate can simultaneously detect Raman signals of Rh6G and crystal violet (CV) at concentration of 10−9M. These indicate that the G/GNRs-VA hybrid substrate could provide reliable support for developing environmental detection and biomedical diagnostics.

Visible light-induced charge transfer to improve sensitive surface-enhanced Raman scattering of ZnO/Ag nanorod arrays

Noble-metal/semiconductor heterostructures that show extended multiple functionalities have attracted ever-increasing attention for using as sensitive surface-enhanced Raman scattering (SERS) substrates. Thus the studies of enhanced mechanism for SERS activity are favorable to fabricate other noble-metal/semiconductor heterostructure substrates and exploit their applications. In this study, we take an insight into the enhanced mechanism for SERS activity of Ag nanoparticle-decorated ZnO nanorod arrays (ZnO/Ag NAs) through studying the Raman vibrational signals of rhodamine 6G (R6G) molecules and photoresponse performance under visible light irradiation. Visible light photoresponse performance shows that the “hot electrons” of plasmonic Ag nanoparticles (NPs) are excited to the conduction band (CB) of ZnO nanorod arrays (ZnO NAs) due to the surface plasmon resonance (SPR). Used as a surface-enhanced Raman scattering (SERS) substrate to test Raman signals of rhodamine 6G (R6G) molecules, the prepared ZnO/Ag NAs show superior SERS performance compared to pure Ag NPs substrate. The visible light photoresponse activities and Raman performances experimentally show that the superior SERS performance of ZnO/Ag NAs is attributed to an effective charge transport within the plasmonic Ag, semiconductor ZnO and R6G molecule. In the charge transport process, the “hot electrons” of Ag NPs are first excited by visible light to the CB of semiconductor ZnO, and then to the lowest unoccupied molecular orbital (LUMO) level of R6G molecule. This work demonstrates that the SERS activity of semiconductor-based hybrid Raman substrate can be significantly improved by effectively turning the charge transport within the hybrid substrate.

Raman probe based on hollow-core microstructured fiber

Surface-enhanced Raman scattering (SERS) technology can effectively enhance the Raman signal of sample molecules. It has a higher sensitivity to detect biomolecule and thus has many potential applications in biochemistry. The combination of hollow-core microstructured fiber and SERS technology not only enables remote real-time and distributed detection, but also can increase the effective action area between the light field and the object to be measured, and further reduce silica glass background signal that is unavoidable in traditional fiber probes. In this paper, the hollow-core microstructure fiber Raman probes with excellent performance are investigated from the aspects of fiber preparation and SERS experi-mental testing. First, we design and manufacture a kind of hollow-core microstructured fiber with multi-bands in the visible and near-infrared wavelength. The fibers show good light guide performance and thus can fully meet the requirements for surface-enhanced Raman excitation and signal transmission. At the same time, the large core size facilitates the coupling of excitation light, and provides enough room for the test object and the light field. Then, this hollow-core microstructured fiber is used in surface-enhanced Raman experiment. A layer of nano-Ag film is modified on the inner surface of the hollow-core microstructure fiber to prepare the SERS probe by the vacuum physical sputtering method, and Rhodamine 6G (R6G) alcohol solutions with different concentrations are prepared by the dilution method. The hollow-core microstructured fiber deposited with the Ag nano-film is immersed in R6G alcohol solution for 2 min. The alcohol solution of R6G is sucked into the air hole of the hollow-core microstructured fiber by the capillary effect. Then this fiber with R6G alcohol solution is placed in a drying oven at 40 ℃ for 3 h until the alcohol solvent in the air hole is completely volatilized. After that, this fiber is taken out and tested under a detection environment full with air. The fiber SERS probes are tested by microscopic confocal Raman spectroscopy, then the Raman spectra of R6G alcohol solvents with different concentrations are obtained. An R6G Raman signal with a concentration as low as 10-9 mol/L is successfully detected on the front side of the probe. In the far-end back-side detection mode, the detected concentration of SERS probe can be less than 10-6 mol/L. The designed hollow-core microstructured fiber probe has a simple structure and is easy to prepare and test. Compared with the traditional optical fiber, it has advantages of large effective area for the test object and the light field, small interference from the silica glass background signal. This hollow-core microstructured fiber probe has wide application prospects in biochemical detection and other fields.

Comparison of surface-enhanced Raman scattering (SERS) effectiveness of Au nanoparticles/cicada wing substrates prepared by different methods

Two different types of Au nanoparticles (Au)/cicada wing (CW) arrays were synthesized by chemical reduction impregnation method and magnetron sputtering technique, respectively. And three-dimensional (3D) Au/CW-c (prepared by chemical reduction impregnation method) arrays and Au/CW-m (prepared by DC magnetron sputtering system) substrate were used as active substrates for SERS. The morphologies and Raman signals of the synthesized Au/CW-c and Au/CW-m substrates were characterized by field emission scanning electron microscopy (FE-SEM) and Raman system. Characterizations of the synthesized Au/CW-c and Au/CW-m substrates exhibited outstanding SERS properties. By comparing the enhanced Raman signal of Rhodamine 6G (R6G), it was found that the Au/CW-m substrate was more sensitive than Au/CW-c substrate. The results showed that the limit of detection (LOD) for R6G was as low as 10−8M for the Au/CW-m substrate. The enhancement factors (EF) were calculated to be 5.09×104 for the Au/CW-c substrate and 1.12×106 for the Au/CW-m substrate. This phenomenon is due to the fact that the high-dense SERS “hot spots” where the collective resonance of the absorbed electrons enhances contribute to the high SERS enhancement of Au/CW-m substrate. What we have found provides a promising approach to the rapid and sensitive detection of trace of organic pollutants.

Integrated Surface-Enhanced Raman Spectroscopy (SERS) Chip Based on a Total Reflection Liquid Core Waveguide.

This study proposes a surface-enhanced Raman scattering (SERS) chip integrated with a liquid core waveguide. Due to the total reflection, the chip suppresses the leaky waveguide mode and enables a long propagation distance for SERS signal collection. A 10 nM rhodamine 6G Raman signal was obtained using a QE65000 portable microspectrometer at a low excitation power intensity of 14.5 W/cm2. The proposed SERS chip was also used to detect the SERS spectrum of a silkworm DNA solution, the structural information of which was clearly shown. In addition, due to the lower excitation power density, damage to the structure of the biomolecule was avoided.

High sensitivity and homogeneity of surface enhanced Raman scattering on three-dimensional array–film hybrid platform

We design and fabricate a substrate based on a three-dimensional array–film hybrid structure used for surface enhanced Raman scattering (SERS). This substrate exhibits improvements both in sensitivity and homogeneity for the Raman signals. As a result, the substrate increases the Raman signal of Rhodamine 6G by 12.3 times under the same measurement conditions, compared with conventional gold array sitting directly on a silica wafer. The sensitivity of SERS can be easily tuned by changing the thickness of SiO2 separation. Meanwhile, the relative standard deviations are achieved to be less than 10%. This array–film hybrid structure provides a promising approach for future SERS applications.

High Raman-to-fluorescence ratio of Rhodamine 6G excited with 532 nm laser wavelength using a closely packed, self-assembled monolayer of silver nanoparticles.

A highly efficient Raman-to-fluorescence ratio of Rhodamine 6G is obtained by means of 532 nm laser wavelength, which is in close proximity of the dye's absorption maximum. Closely packed, gap-filled self-assembled monolayers of silver nanoparticles were produced to observe the Raman signals of Rhodamine 6G. Two mechanisms contribute to detect the Raman signals of the fluorescent sample: surface-enhanced Raman scattering (SERS) and nanomaterial surface energy transfer (NSET). Self-assembled monolayers of silver nanoparticles with different coverage densities and also those filled with probe molecules were prepared through variations of the substrate's immersion time in a nanoparticle solution and drying the substrate, respectively. Examination of the effects of these two factors on the plasmonic response and SERS efficiency of the substrate revealed that in a gap-filled dense coverage, near-field interactions dominate, which remarkably increase the Raman-to-fluorescence ratio (RFR). To have a perfect dense coverage, the efficient immersion time was obtained at about 48 h. Drying the substrates also caused further enhancement in RFR through filling interparticle spaces with dye molecules and, accordingly, an increase in NSET efficiency.

Mesoporous Ag nanocubes synthesized via selectively oxidative etching at room temperature for surface-enhanced Raman spectroscopy

Silver nanocubes enriched with 100 facets have been extensively used for surface-enhanced Raman scattering. Herein, we report a new water-phase synthesis method for well-defined Ag nanocubes with tunable sizes via a two-step procedure at room temperature. First, irregularly shaped Ag nanoparticles (INPs) were prepared by reducing silver ammonia solution using ethylal. Second, the agglomerated INPs were selectively etched with HNO3 and Cl− to yield 100 facet-rich mesoporous Ag nanocubes. The mechanism of Ag-nanocube formation and growth was investigated in detail by elucidating the involved chemical reactions and physical changes at each step during the synthesis. The addition of Cl− anions was responsible for facilitating Ag nanoparticle growth by removing surface-adsorbed AgCl+ species, thereby eliminating inter-particle repulsive forces. This agglomeration was found crucial for the subsequent selective oxidation of Ag nanoparticles because the protective agent used, polyvinylpyrrolidone (PVP), was the most effective one for adsorption on the surfaces of Ag nanoparticles of size greater than approximately 50 nm. Importantly, mesopores were found inside the Ag nanocubes; this can be attributed to the unavoidable imperfect packing during the agglomeration of INPs. The newly prepared Ag nanocubes were further used to enhance the Raman signal of rhodamine 6G, which is capable of reducing the detection limitation to 10−16 mol·L−1.

Green synthesis, characterization of Au–Ag core–shell nanoparticles using gripe water and their applications in nonlinear optics and surface enhanced Raman studies

In recent years there has been excessive progress in the ‘green’ chemistry approach for the synthesis of gold and silver nanoparticles. Bimetallic nanoparticles have gained special significance due to their unique tunable optical properties. Herein we report a facile one-pot, eco-friendly synthesis of Au–Ag bimetallic core–shell nanoparticles using gripe water as reducing as well as stabilizing agent. The as-synthesized Au–Ag nanoparticles are characterized using UV–Vis spectroscopy to determine the surface plasmon resonance, and using transmission electron microscopy to study the morphology and the particle size. The optical nonlinearity of the bimetallic nanoparticles investigated by z-scan technique using femtosecond Ti:sapphire is in the order of 109. The nonlinear optical parameters such as the nonlinear refractive index n2, nonlinear absorption coefficient β and the third order nonlinear susceptibility χ3 are measured for various wavelengths from 700 nm to 950 nm. The Au–Ag nanoparticles are also used in surface enhanced Raman spectroscopic studies to enhance the Raman signals of rhodamine 6G.

Fabrication of Gold Nanoparticles on Porous Silicon and Its Application to (Bio) Chemical Sensing Platforms

Traditional electrodes, such as glassy carbon, gold, and ITO, are most commonly used, but they are difficult to fabricate, limited in sensor design, and expensive to manufacture. In contrast, nano-scaled silicon has attracted considerable interest due to its potential advantages such as controllable pore size, low toxicity, and recyclable materials. It has been studied to explore its immense potential applications in electronics, actuators, and sensors. In particular, porous silicon has emerged as a promising material for applications in drug delivery, diagnostics, and (bio) chemical sensing owing to its high surface area, tunable pore structure, and biocompatibility [1]. In recent, to fabricate and assess the utilities of nanoparticles hybrid device, research efforts have focused on using novel metal nanoparticles to modify electrode surface in order to enhance the electrocatalytic activity of the electrode. In this study, we present the patterning of gold nanoparticles (AuNPs) on porous silicon using electrochemical deposition. The fabricated electrodes were used as the electrochemical sensing platforms for hydroxylamine detection and as surface-enhanced Raman spectroscopy (SERS) substrates. The formation of porous structure was performed by electrochemical etching of n-type crystalline silicon. The morphology and structure of porous silicon could be easily controlled by changing electrochemical etching conditions such as HF concentration, current density, anodization time, and illumination. The morphologies of the fabricated porous silicon substrates were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) (Figures 1A and B). To extend the application of the porous silicon substrates to sensing platforms, gold nanoparticles were deposited electrochemically, and used as the electrodes for hydroxylamine detection. The size and density of AuNPs could easily be adjusted, and the morphologies of the AuNPs deposited porous silicon (AuNPs-porous silicon) substrates were investigated by scanning electron microscopy (Figures 1C and D). Figure 1 Images of porous silicon by (A) SEM and (B) AFM. SEM images of (C) AuNPs-crystalline silicon and (D) AuNPs-porous silicon. The scale bars are 5μm. Hydroxylamine plays an important role as a reducing agent and an intermediate in industry and biological processing, respectively.However, hydroxylamine is well- known mutagen, moderately toxic and harmful to microorganisms that could interfere with biological sewage plant performance. Because of the industrial and pharmacological significance, the highly sensitive detection of hydroxylamine is interested in this study. Figure 2A show the cyclic voltammetry for the oxidation of 1 mM hydroxylamine. The AuNPs-porous silicon electrodes exhibited higher anodic peaks compared to AuNPs-crystalline silicon electrodes. The anodic peaks were attributed to the oxidation of hydroxylamine. Hydroxylamine oxidation on the AuNPs-porous silicon electrode occurred at 0.45 V (curve f), which was lower than that on the AuNPs-crystalline silicon electrode (curve e). As another application, AuNPs-porous silicon substrates were used as platforms for the SERS. Among biophysical and biochemical analysis, SERS is expected as a new active tool because of its high sensitivity, the wide applicability, little to no sample preparation requirement, and straight forward sample identification [2]. The SERS activity was investigated by measuring the Raman signal of Rhodamine 6G (R6G) absorbed onto the as-prepared substrates; AuNPs-porous silicon and AuNPs-crystalline silicon. The SERS spectra showed that the AuNPs-porous silicon substrate emitted a strong R6G Raman signal compared to AuNPs-crystalline silicon substrate due to the large active area of AuNPs on porous silicon substrates. In addition, the Raman signals on silver NPs-porous silicon were higher than those on AuNPs-porous silicon. We expect that the developed AuNPs-porous silicon substrates can be used as various types of (bio) chemical sensing platforms. Figure 2 (A) Cyclic voltammetry of the oxidation of 1.08 mM Hydroxylamine in 0.1 M PBS (pH 7.0) on (a) crystalline silicon, (b) AuNPs-crystalline silicon, (c) porous silicon, and (d) AuNPs-porous silicon at a scan rate of 30mV/s. (B) SERS spectra of 300μM R6G on (a) AuNPs-porous silicon (red) and (b) AuNPs-crystalline silicon (blue). References C. K. Tsang, T. L. Kelly, M. J. Sailor, Y. Y. Li, ACS Nano (2012) 6 10546-10554X. Gong, Y. Bao, C. Qiu, C. Jiang, ChemComm (2012) 48 7003-7018