Search

In this study, we propose an easy and cost-effective method to improve the refractive index (RI) sensitivity of hierarchical aluminum (Al) nanocap arrays (HAlNAs) that are suitable for RI sensing applications. By adjusting the deposited Al thickness, deposition rate, and period, HAlNAs with tunable plasmonic and sensing properties could be achieved. The optimal sensitivity could reach 631 nm/RIU, and the detection limit of adenine ethanol solution with different concentration was as low as 1 × 10–6 M. The experimental results confirmed that the RI sensitivity of the proposed sensor was primarily related to the period and deposited Al thickness. Moreover, a higher deposition rate could narrow the full width at half-maximum (FWHM) of the reflection spectra, resulting in a higher figure of merit (FOM). The simulated electric field (EF) distribution revealed that the high RI sensitivity could be attributed to the strong coupling between propagating surface plasmon polaritons (PSPPs) and localized surface plasmon resonance (LSPR). In addition, HAlNAs with larger periods could generate a greater hot spot density, resulting in higher sensing sensitivity. The results of this study provide a method to easily fabricate Al-based RI sensors that exhibit great promise for the development of highly sensitive and selective biosensors. [ABSTRACT FROM AUTHOR]

Herein, we proposed a simple non-lithographic way to fabricate hierarchical Al nanopit arrays performed as deep ultraviolet (DUV, 200–300 nm) refractive index sensing. Only by adjusting the Al deposition thickness on the Al nanopit array, the hierarchical Al nanopit arrays with tunable plasmonic properties in the DUV region were obtained. The prepared hierarchical Al nanopit arrays are of very good time stability and its RI sensitivity and concentration detection limit of adenine ethanol solution reach 311 nm/RIU and 5 × 10 − 6 M , respectively, as the Al deposition thickness is 60 nm. Furthermore, the electric field distribution simulation results show that high RI sensing characteristic are mainly attributed to the local surface plasmon resonance. This investigation provides a facile way to develop low cost, high efficient and easily fabricated Al-based RI sensor in the DUV region. [ABSTRACT FROM AUTHOR]

Abstract: Gold colloids were synthesized via mixing the aqueous solution of HAuCl4 and Triton X-100 at room temperature. The gold sol samples were quickly obtained during first 2h then the samples were placed for 8h to ensure they were completely stable. The colour of most samples turned to violet red. But the sample with 0.5ml TX-100 remained colorless. During synthesizing, UV–vis absorption spectra were recorded every 10s. By studying the synthesis time–dependent surface plasmon resonance (SPR), we found that the growth of gold colloids presented an exponential increase form. By analyzing the TX-100 concentration dependence of absorption peak, the effect of TX-100 concentration on gold colloid diameter was studied and the gold colloid''s final dimension was resulted from competition between reducing speed and coating speed. [Copyright &y& Elsevier]

Abstract: Suspended gold nanorods with mean aspect ratio 2.5 have been synthesized via electrochemical method. Resonance scattering properties have been studied. Two scattering peaks fixed at 400 and 640nm are due to the scattering of the gold nanorods via coupling to the transverse and longitudinal surface plasmon resonance. The quasi-static calculation results indicate that with the increasing aspect ratio of the nanorods, the longer wavelength scattering peak red shifts linearly and the shorter wavelength peak blue shifts non-linearly. When aspect ratio a/b =1.0, ellipse degenerate to sphere and the two peaks unite into one peak at 450nm. [Copyright &y& Elsevier]

Nanostructure-based localized surface plasmon resonance (LSPR) sensing have great potential for refractive index (RI) detection in the area of life science, chemical and food safety. Recently, the studies of aluminum (Al)-based nanostructures for sensing have attracted a large attention because aluminum is a cost-effective material and have excellent plasmonic characteristics from UV to near-infrared ranges. However, the fabrication of Al nanostructures used for sensing mainly focus on lithography techniques which are complex, expensive. Here, a facile method for the fabrication of hierarchical Al nanocap arrays used as LSPR sensing device was investigated. By only controlling the deposited Al thickness onto barrier layer surface of anodic aluminum oxide (AAO) template, the hierarchical Al nanocap arrays with tunable plasmonic wavelength ranging from 331 nm to 428 nm were obtained. The RI sensitivity of 80 nm hierarchical Al nanocap array is 358 nm/RIU and shows a good consistency with the FDTD simulation result. The concentration detection limit of adenine aqueous and ethanol solution are 1 × 10 − 6 M and 1 × 10 − 5 M , respectively. The results provide a new approach for developing an inexpensive, efficient, and mass-produced Al nanostructure sensor. • A facile AAO template-assisted method for the fabrication of hierarchical Al nanocap arrays performed as LSPR sensing was reported. • By controlling the deposited Al thickness, the LSPR wavelength can be regulated from 331 to 428 nm. • The RI sensitivity was 358 nm/RIU. • The adenine detection limit down to 1 × 10 − 6 M for water solution and 1 × 10 − 5 M for ethanol solution. [ABSTRACT FROM AUTHOR]