Analysis of Nitrogen Dioxide in Environment

As a severe environmental pollutant, detection and quantitation of nitrogen dioxide (NO2) have been studied for centuries. In this review, recent progress of NO2 analysis in the atmosphere will be summarized. Four major types of detection technologies, including traditional chemical detection, optical detection, solid-state field effect transistor detection, and other detection technology are covered. The standard method employed by the US EPA, which is based on luminol, is the most reliable and robust method that is used for fully validated monitoring. In the past two decades, accompanying the fast development of electrical engineering and integrated circuit, micro to nanoscale gas sensors have been gaining more and more attention. Application of novel materials including nano wires and graphene also leads to a new era of research and development of sensors.

Real-time detection of Cu(Ⅱ)with PEDOT:PSS based organic electrochemical transistors

Copper is an essential element in the environment and the human body, but at the same time, exposure to high concentrations of Cu2+ions will potentially lead to acute toxicity and various neurodegenerative diseases. Thus, it is of great significance for the development of highly sensitive and selective strategies for the detection of Cu2+ions. Here, we report a highly efficient poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) based organic electrochemical transistor (OECT) sensor, for real-time Cu2+ions detection. The detection limit of the OECT device is as low as 100 nM, far beyond the sensitivity required for practical uses. The detection mechanism may base on the chemical reactivity of Cu2+ions oxiding the PEDOT:PSS in solution both in absence and presence of the base potential. The OECT devices also exhibit excellent selective response to Cu2+ions rather than other metal ions. Finally, we also demonstrate the determination of Cu2+ions in tap water with the OECT Cu2+sensor. Considering the high sensitivity and selectivity, as well as the real-time and low cost features of our Cu2+OECT sensor, it is ideal for portable and disposable applications for environment monitoring and public health. © 2017, Science China Press and Springer-Verlag Berlin Heidelberg.

Detection of chemicals in water using a three-dimensional graphene porous structure as liquid-vapor separation filter

In this study, we report the utilization of a three-dimensional （3D） porous graphene structure as liquid-vapor separation filter, which allows the passage of chemical vapors while blocking liquid chemicals and water. The blockage of liquid chemicals and water from semiconducting sensing regions is required to avoid abnormal transistor characteristics. In order to impart omniphobic characteristics, a （heptadecafluoro-1,1,2,2-tetrahydrodecyl）trichlorosilane （HDF-S） self-assembled monolayer was coated on the surface of the 3D porous graphene structure. The concentration of chemical agents in water could be consistently detected by observing the shift in the threshold voltage in the oxide nanowire transistor covered by the HDF-S self-assembled 3D graphene structure. The proposed monitoring method is expected to offer means for application in different environments by providing a stable sensing performance.

Preparation of Functional Magnetic Nanoparticles and its Application in Diagnostic Analysis

The magnetic nanoparticles modified with carboxyl functional group were synthesized and characterized. These nanoparticles covalently bound with hepatitis B surface antibody（HBsAb）, were used to detect hepatitis B surface antigen （HBsAg） in immunovoltammetry. The detection limit was found to be 0.06 ng/mL, which is much higher than that of enzyme-linked immunosorbent assay （ELISA） used in clinical analysis.

Polymer-coated symmetrical metal-cladding waveguide for chemical vapor detection with high sensitivity

An optical platform for sensitive detection of chemical vapor based on a polymer-coated symmetrical metal-cladding waveguide is proposed.The diffusion of chemical vapor usually leads to a combinational effect in the polymer layer,i.e.,swelling and refractive index change.Owing to the high sensitivity of ultrahigh-order modes,the vapor-induced effect will give rise to a dramatic variation of the reflected light intensity.For proof-of-concept,a good linearity and a low detection limit of toluene and benzene are experimentally demonstrated with an amorphous Teflon AF polymer layer.

Porous silicon biosensor for detection of variable domain of heavy-chain of HCAb antibody

In this paper, we produce porous silicon （PSi） by electrochemical etching, and it is the first time to evaluate the performance of label-free porous silicon biosensor for detection of variable domain of heavy chain of heavy-chain antibody （VHH）. The binding of hen egg white lysozyme （HEWL） and VHH causes a red shift in the reflection spectrum of the biosensor. The red shift is proportional to the VHH concenlration in the range from 14 gg.ml-I to 30 pg.ml~ with a detection limit of 0.648 ng.ml~. The research is useful for the development of label-free biosensor applied in the rapid and sensitive determination of small molecules.

Parameters optimization of π-phase-shifted long-period fiber grating for gas sensing

The gas-sensitive film coated π-phase-shifted long-period fiber grating(LPFG),consisting of two same long-period fiber gratings cascaded by a regular fiber with length of half of the grating period,is proposed for gas sensing.The sensitivity of the sensor is defined by the change rate of the transmission at specific wavelength with respect to the film refractive index.The qualitative and numerical analyses show that to get a high sensitivity,the optimal coupling strength of each long-period fiber grating is √2 π/4.With this coupling strength,the longer the grating is,the higher sensitivity the sensor has.By choosing appropriate grating period,a high sensitivity for the film with a certain refractive index and thickness can be attained.

Tagged molecule induced nanoparticle aggregation:Raman reporter-labeled immuno-Au aggregate as immuno-sensor

A novel structure with high surface enhanced Raman scattering （SERS） activity and bio-specificity as a SERS-based immuno-sensor （named as Raman reporter-labeled immuno-Au aggregate） is demonstrated and employed for protein detection. In each fabrication process, the features of those aggregates are obtained and characterized by ultraviolet-visible （UV-Vis） extinction spectra, transmission electron microscopy （TEM） images, scanning electron microscopy （SEM） pictures, and SERS spectra. Experimental results indicate that proper amounts of the reporter molecules can result in the moderate aggregation morphologies of gold nanoparticles. Compared with the previously reported method using Raman reporterlabeled immuno-Au nanoparticles, more sensitive SERS-based protein detection is realized with this novel immuno-sensor.

Translation of the long-term fundamental studies on viral DNA packaging motors into nanotechnology and nanomedicine

Many years of fundamental studies on viral genome packaging motors have led to fruitful applications.The double-stranded DNA(dsDNA)viruses package their genomes into preformed protein shells via nanomotors including several elegant and meticulous coaxial modules.The motor is geared by the hexameric RNA ring.An open washer displayed as hexametric string of phi29 motor ATPase has been reported.The open washer linked into a filament as a queue with left-handed chirality along the dsDNA chain.It was found that a free 5′-and 3′-dsDNA end is not required for one gp16 dimer and four monomers to assemble into the hexametric washer on dsDNA.The above studies have inspired several applications in nanotechnology and nanomedicine.These applications include:(i)studies on the precision motor channels have led to their application in the single pore sensing;(ii)investigations into the hand-in-hand integration of the hexametric pRNA ring have resulted in the emergence of the new field of RNA nanotechnology;and(iii)the studies on the motor stoichiometry of homologous multi-subunits that subsequently have inspired the discovery of new methods in highly potent drug development.This review focuses on the structure and function of the viral DNA packaging motors and describes how fundamental studies inspired various applications.Given these advantages,more nanotechnological and biomedical applications using bacteriophage motor components are expected.

Fiber-optic surface plasmon resonance-based sensor with AZO/Au bilayered sensing layer

We describe a surface plasmon resonance-based fiber sensor based on a side-polished graded-index mul- timode fiber, in which an Al-doped zinc oxide/gold （AZO/Au） bilayer is deposited on the side-polished surface of the fiber core to improve the detection sensitivity of the device. The AZO/Au layer is used as the active sensing member of the device with a combination of a 75-nm-thick AZO layer and a 40-nm-thick Au layer. Such a device is then applied to the concentration measurement of CHaCOONa solutions, as an example showing a good response to concentration variation. The results indicate that the additional AZO layer in the active sensing member may lead to higher detection sensitivity and greater measurement stability in the measurements of solution concentration.