Ethanol Vapor Sensing Properties of Triangular Silver Nanostructures Based on Localized Surface Plasmon Resonance

A sensitive volatile organic vapor sensor based on the LSPR properties of silver triangular nanoprisms is proposed in this paper. The triangular nanoprisms were fabricated by a nanosphere lithography (NSL) method. They have sharp vertices and edges, and are arranged in an ideal hexangular array. These characteristics ensure that they exhibit an excellent LSPR spectrum and a high sensitivity to the exterior environment changes. The LSPR spectra responding to ethanol vapor and four other volatile organic vapors—acetone, benzene, hexane and propanol—were measured with a UV-vis spectrometer in real time. Compared with the other four vapors, ethanol exhibits the highest sensitivity (∼0.1 nm/mg L−1) and the lowest detection limit (∼10 mg/L) in the spectral tests. The ethanol vapor test process is also fast (∼4 s) and reversible. These insights demonstrate that the triangular nanoprism based nano-sensor can be used in ethanol vapor detection applications

Sensitive Gas-Sensing by Creating Adsorption Active Sites: Coating an SnO₂ Layer on Triangle Arrays

It is a widely used strategy to enhance gas sensor sensitivity by improving its surface area, but this process, including bonding the sensing block into a device substrate, needs complex manipulations. This work shows a concept of creating adsorption active sites, in which an SnO2 layer (6.85 nm thin) is directly coated on a triangle array substrate to be of an ensemble of triangular convex adsorption active sites (TCAASs). The resultant SnO2 gas sensors, with TCAAS periods ranging from 289 to 1154 nm, exhibit an adsorption-active-site-dependent sensitivity and present a low detection limit of around 6 ppm ethanol gas at room temperature. By characterizations of Kelvin force microscopy, a large surface potential variation exists on these adsorption active sites after introducing ethanol gas, distinctly showing a local adsorption enhancement. These results confirm that the creation of adsorption active sites can efficiently increase surface adsorption of a sensor to realize its sensitive gas-sensing

The recent progress on silver nanoparticles: Synthesis and electronic applications

Nanoscience enables researchers to develop new and cost-effective nanomaterials for energy, healthcare, and medical applications. Silver nanoparticles (Ag NPs) are currently increasingly synthesized for their superior physicochemical and electronic properties. Good knowledge of these characteristics allows the development of applications in all sensitive and essential fields in the service of humans and the environment. This review aims to summarize the Ag NPs synthesis methods, properties, applications, and future challenges. Generally, Ag NPs can be synthesized using physical, chemical, and biological routes. Due to the great and increasing demand for metal and metal oxide nanoparticles, researchers have invented a new, environmentally friendly, inexpensive synthetic method that replaces other methods with many defects. Studies of Ag NPs have increased after clear and substantial support from governments to develop nanotechnology. Ag NPs are the most widely due to their various potent properties. Thus, this comprehensive review discusses the different synthesis procedures and electronic applications of Ag NPs

Investigation of metal nanomaterials as a sensing element in LSPR-based optical fibre sensor development

This thesis aims to explore and demonstrate the potential of using optical fibres both as a waveguide material and a transducer for wide sensing applications, based on a comprehensive review of the localised surface plasmon resonance (LSPR) phenomenon, which occurs at a nanoscale level when light interacts with metallic nanoparticles at a resonance wavelength. The LSPR effect of metallic nanomaterials has shown a strong dependence on the local surrounding environment. A small change for example in the refractive index or in the solution concentration can result in a variation in the LSPR spectrum. Based on this underpinning sensing mechanism, a portable system using an optical fibre coated with gold nanoparticles (AuNPs) as a sensing probe has been developed and tested for the refractive index measurement. Coupled with this, a systematic approach has been developed and applied in this work to optimize the performance of the developed system by considering several key factors, such as the size of nanoparticles produced, pH, coating time and coating temperature. The above optimised probes coated with gold-nanoparticles are further cross-compared with those optimized but coated with gold nanorods with a high aspect ratio. Both types of probes are also prepared for a specific biosensing application based on the antibody-antigen interaction to create wavelength-based sensors for the detection of anti-human IgG. Both probes have exhibited excellent refractive index (RI) sensitivity, showing ~914 nm/RIU (refractive index unit) for the probe coated with gold nanoparticles and ~601 nm/RIU for the one coated with gold nanorods. When using the modified probes for the detection of anti-human IgG, both probes are able to achieve a good LOD (limit of detection) at 1.6 nM. Based on the above cross-comparison, further research has been undertaken to explore the potential of nanoparticles of the alloy of gold and silver, with an aim to combine the robustness of gold and the excellent LSPR effect of silver. To do so, various alloy particles with varied gold/silver ratio and sizes have been prepared and tested for their respective refractive index sensitivities. The probe coated with alloy particles with bigger size and higher silver content has shown better performance in RI sensing. The work has shown a clear relationship between the size of alloys, the content ratio of alloys and RI sensitivity. Research has also been undertaken in this thesis to explore the excellent LSPR effect of hollow nanoparticles resulting from the enhanced coupling between the interior and exterior of the hollow particles. Gold hollow nanocages have been successfully synthesised and tested with different hollowness and a LSPR sensor coated with gold nanocages has shown an excellent sensitivity as high as ~1933 nm/RIU, which is more than 3 times higher than that coated with AuNPs. This result has confirmed that a significant improvement in sensitivity can be made possible for further biosensing as well as chemical sensing applications