A theoretical study of a plasmonic sensor comprising a gold nano-disk array on gold film with a SiO_2 spacer

A plasmonic refractive index(RI) sensor with high RI sensitivity based on a gold composite structure is proposed.This composite structure is constructed from a perfect gold nano-disk square array on a gold film, with a SiO_2 spacer. The reflection spectra of the composite structure, with analyte RI in the range of 1.30 to 1.40, are theoretically studied using the finite-difference time-domain method. The incident light beam is partly coupled to the localized surface plasmons(LSP) of the single nano-disks and partly transferred to the propagating surface plasmons(PSP) by grating coupling. The reflectivity is nearly zero at the valley of the reflection spectrum because of the strong coupling between LSP and PSP. Also, the full width at half maximum(FWHM) of one of the surface plasmon polaritons(SPPs) modes is very narrow, which is helpful for RI sensing. An RI sensitivity as high as 853 nm/RIU is obtained. The influence of the structure parameters on the RI sensitivity and the sensor figure of merit(FOM) are investigated in detail. We find that the sensor maintains high RI sensitivity over a large range of periods and nano-disk diameters. Results of the theoretical simulation of the composite structure as a plasmonic sensor are promising. Thus, this composite structure could be extensively applied in the fields of biology and chemistry.

Ultra wide sensing range plasmonic refractive index sensor based on nano-array with rhombus particles

We propose a two-dimensional metal grating with rhombus particles on a gold film structure for refractive index sensing due to its perfect absorption at near-infrared wavelength.Via two-dimensional metal grating coupling,the incident light energy is effectively transformed into the surface plasmons which propagate along the upper surface of the gold film and interact with the surrounding environment in a wide range.The plasmonic resonance mechanism of the structure is discussed in detail by theoretical analysis and finite-difference time-domain method.After optimizing the geometrical parameters,the designed structure shows the sensing performance with a refractive index sensitivity of 1006 nm/RIU.More importantly,this plasmonic refractive index sensor achieves an ultra wide refractive index sensing range from 1.0 to 2.4 with a stable sensing performance.The promising simulation results of the structure show that the sensor has a broad application prospect in the field of biology and chemistry.

Transmembrane transport of polycyclic aromatic hydrocarbons by bacteria and functional regulation of membrane proteins

In recent years,increasing research has been conducted on transmembrane transport processes and the mechanisms behind the microbial breakdown of polycyclic aromatic hydrocarbons(PAHs),including the role of membrane proteins in transmembrane transport and the mode of transmission.This article explains the adsorption,uptake and transmembrane transport of PAHs by bacteria,the regulation of membrane protein function during the transmembrane transport.There are three different regulation mechanisms for uptake,depending on the state and size of the oil droplets relative to the size of the microbial cells,which are(i)direct adhesion,(ii)emulsification and pseudosolubilization,and(iii)interfacial uptake.Furthermore,two main transmembrane transport modes are introduced,which are(i)active transport and(ii)passive uptake and active efflux mechanism.Meanwhile,introduce the proteomics and single cell analysis technology used to address these areas of research,such as Isobaric tags for relative and absolute quantitation(iTRAQ)technology and Nano Secondary ion mass spectrometry(Nano-SIMS).Additionally,analyze the changes in morphology and structure and the characteristics of microbial cell membranes in the process of transmembrane transport.Finally,recognize the microscopic mechanism of PAHs biodegradation in terms of cell and membrane proteins are of great theoretical and practical significance for understanding the factors that influence the efficient degradation of PAHs contaminants in soil and for remediating the PAHs contamination in this area with biotechnology.