Optimization and characterization of Au cuboid nanostructures as a SERS device for sensing applications (original) (raw)
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Electrochemical Growth of Gold Nanostructures for Surface-Enhanced Raman Scattering
The Journal of Physical Chemistry C, 2011
We demonstrate a facile fabrication of gold nanostructures including Au nanoplates (NPs), Au nanothorns (NTs), and Au nanowires (NWs) on indium tin oxide substrates via electrochemical growth. A simple two-electrode electrochemical deposition system was applied for the fabrication process. Dense Au nanostructures were grown directly on an Au seeding layer on the substrate. After 48 h, the Au NPs were 2-5 μm in width and 150-200 nm in thickness. The Au NTs were 1-3 μm in height, 300-500 nm in bottom side width, and 20 nm at the apex. The Au NWs were 30-80 nm in diameter and about 20 μm in length. The entire process was template-free and economical. We investigated the correlation between surface plasmon resonance (SPR) and surface enhanced scattering (SERS) effects of the Au nanostructures with different excitation wavelengths. By using the SPR absorption maxima of the nanostructures as the excitation wavelengths for SERS, the highest SERS enhancements were achieved. SERS effects of the Au NWs were investigated further. We discovered that the length and the density of the Au NWs affected the SERS performance significantly. The result is rationalized by the amount of "hot spot" generated at the crossing of the Au NWs. With the Au NWs, Rhodamine 6G can be detected at a concentration as low as 10-9 M.
Sensors and Actuators B: Chemical, 2016
We report on an improvement way of the SERS signal of Au triangular nanoprisms for a highly sensitive detection of chemical molecules. This improvement is obtained by a simple addition of a gold reflective layer under Au nanoprisms. Using the same Au triangular nanoprisms obtained by nanosphere lithography, we studied experimentally the thickness effect of this gold underlayer on the SERS intensity of the triangular nanoprisms. We demonstrated that this SERS intensity increased with the thickness of the gold reflective underlayer, and this is due to the increment of the Au underlayer reflectivity. Thus, we showed that the metallic reflective underlayer has an important key for SERS enhancement. Indeed, enhancement factors of 10 8 were found for the most important thickness of the gold underlayer.
Journal of Nanoscience and Nanotechnology, 2016
Ordered arrays of Au-nanorod-tips protruding from an anodic aluminum oxide (AAO) template are reported as reproducible and active surface-enhanced Raman scattering (SERS) substrates. The Au-nanorods were grown in the nanochannels of the AAO template by use of alternative current electrodeposition, then the template was strengthened using a polymer, and finally the template bottom side was selectively etched to expose the Au-nanorod tips. By controlling the thinning of the AAO-porewalls, the inter-nanorod-gaps were tuned to ∼5 nm, forming dense and uniform nanogap induced "hot spots" among the adjacent Au-nanorod tips. As a result, the electromagnetic field of the Au-nanorod-tip arrays was uniformly enhanced, and demonstrated high SERS sensitivity with good signal reproducibility. The Au-nanorod-tips have the potential to be used in SERS-based applications in order to rapidly detect trace pollutants in the environment.
Plasmonics, 2016
Highly ordered arrays of vertically aligned Au nanorod arrays consisting of agglomerated nanoparticles are fabricated by porous anodic aluminum oxide (AAO) template-assisted electrochemical deposition. The Au nanorod arrays with rough surfaces are then transformed to smooth surfaces by a subsequent thermal annealing step. The surface-enhanced Raman scattering (SERS) intensity of the Au nanorod arrays with rough and smooth surfaces was compared to investigate the morphology dependence of SERS. The Au nanorod arrays with agglomerated structures demonstrated a highly active SERS effect as abundant nanogaps are created uniformly by combination of hot spots caused by both agglomerated porous structures on each nanorod and inter-rod gaps.
Journal of Materials Science, 2015
Surface Enhanced Raman Scattering is a sensitive and widely used as spectroscopic technique for chemical and biological structure analysis. One of the keys to increase the sensitivity of SERS sensors is to use nanoparticles/nanostructures. Here, we report on the density effect of gold nanodisks on SERS intensity for a highly sensitive detection of chemical molecules. Various densities of gold nanodisks with a height of 30 nm on gold/glass substrate were fabricated by electron beam lithography in order to have a good uniformity and reproducibility. The evolution of the Enhancement Factor with nanodisk density was quantified and compared to numerical calculations. An enhancement factor as high as 2.6×10 7 was measured for the nanodisk with a diameter of 110 nm and a periodicity of 150 nm which corresponds to the biggest density (42.2%).
2022
In this investigation, SERS substrates were synthesized based on the growth of Au nanoparticles (AuNPs) layer over porous support of anodized aluminum oxide (AAO). The enhancement factor (EF) of the SERS substrates was determined by the measurement of Rhodamine 6G (R6G) allowed a detection limit of 10−11 (measured over molar concentration). The AAO was grown by a two-stage anodizing method, and subsequently, an Au precursor layer in different thicknesses was sputtered on each alumina support. The coated samples were heat-treated under nitrogen to promote different spatial distributions of AuNPs on the surface. Au-Np layer was achieved with disordered pore-like as demonstrated by low-pressure Nitrogen adsorption and BET analysis (isotherm curve type IV-H3). The sample that exhibited the strongest SERS effect consisted of a 50 nm Au precursor layer on the AAO support. The method reported in this work is highly reproducible, given its simplicity, with a homogeneous size distribution compared to other methods and other substrates such as Silicon.
Applied Surface Science, 2021
In this investigation, SERS substrates were synthesized based on the growth of Au nanoparticles (AuNPs) layer over porous support of anodized aluminum oxide (AAO). The enhancement factor (EF) of the SERS substrates was determined by the measurement of Rhodamine 6G (R6G) allowed a detection limit of 10 −11 (measured over molar concentration). The AAO was grown by a two-stage anodizing method, and subsequently, an Au precursor layer in different thicknesses was sputtered on each alumina support. The coated samples were heat-treated under nitrogen to promote different spatial distributions of AuNPs on the surface. Au-Np layer was achieved with disordered pore-like as demonstrated by low-pressure Nitrogen adsorption and BET analysis (isotherm curve type IV-H 3). The sample that exhibited the strongest SERS effect consisted of a 50 nm Au precursor layer on the AAO support. The method reported in this work is highly reproducible, given its simplicity, with a homogeneous size distribution compared to other methods and other substrates such as Silicon.
Physica E: Low-dimensional Systems and Nanostructures, 2011
Aligned Ag nanorods were prepared by glancing angle deposition on micro-patterns of silicon fabricated by electron beam lithography, forming hexagonal lattices. Excited by a 633 nm He-Ne laser, Raman scattering of Rhodamine 6G molecules on the hexagonal lattices has been investigated. The enhancement of the Raman signals by the hexagonal lattices was found to be dependent on the separation distance of the micro-patterns, i.e. it reached the maximum when the patterns are separated by $ 200 nm or closely packed, suggesting a coupling effect at the micro-nano scales. This study also provides an idea to further enhance the Raman scattering.
Gold bulletin, 2013
Surface-enhanced Raman spectroscopy (SERS) has enormous potential for a range of applications where high sensitivity needs to be combined with good discrimination between molecular targets. However, the SERS technique has trouble finding its industrial development, as was the case with the surface plasmon resonance technology. The main reason is the difficulty to produce stable, reproducible, and highly efficient substrates for quantitative measurements. In this paper, we report a method to obtain two-dimensional regular nanopatterns of gold nanoparticles (AuNPs). The resulting patterns were evaluated by SERS. Our bottom-up strategy was divided into two steps: (a) nanopatterning of the substrate by e-beam lithography and (b) electrostatic adsorption of AuNPs on functionalized substrates. This approach enabled us to highlight the optimal conditions to obtain monolayer, rows, or ring of AuNPs, with homogeneous distribution and high density (800 AuNPs/μm 2). The nanostructure distributions on the substrates were displayed by scanning electron microscopy and atomic force microscopy images. Optical properties of our nanostructures were characterized by visible extinction spectra and by the measured enhancements of Raman scattering. Finally, we tried to demonstrate experimentally that, to observe a significant enhancement of SERS, the gold diffusers must be extremely closer. If electron beam lithography is a very attractive technique to perform reproducible SERS substrates, the realization of pattern needs a very high resolution, with distances between nanostructures probably of less than 20 nm.