Luyin Zhang

Highly sensitive detection of organophosphorus pesticides by acetylcholinesterase-coated thin film bulk acoustic resonator mass-loading sensor

An acetylcholinesterase-coated thin film bulk acoustic resonator has been developed for the detection of organophosphorus pesticides. The thin film bulk acoustic resonator acts as a robust mass-sensitive transducer for bio-sensing. This device works in thickness shear mode with a resonance at 1.97 GHz. The detection is based on the inhibitory effects of organophosphorus compounds on the enzymatic activity of the acetylcholinesterase immobilized on one of the faces of the acoustic resonator. The enzyme reaction in the substrate solution and the inhibitory effect is observed are real time by measuring the frequency shift. The presence of organophosphorus pesticides can be detected from the diminution of the frequency shift compared with the levels found in their absence. The device exhibits linear responses, good reproducibility, simple operation, portability and a low detection limit of 5.3×10(-11) M for paraoxon. The detection results of organophosphorus pesticide residues in practical samples show that the proposed sensor has the feasibility and sensing accuracy comparable to gas chromatography.

A thin film electro-acoustic enzyme biosensor allowing the detection of trace organophosphorus pesticides

We report an analytical method using a thin film electro-acoustic resonator for the detection of organophosphorus pesticides. The acetylcholinesterase (AChE) enzyme was immobilized on the surface of the resonator. In the presence of organophosphorus compounds, the degree of inhibitory effect of organophosphorus compounds on the AChE activity and the concentration of pesticides were detected in real time by measuring the frequency shift of the resonator. The proposed device has a remarkably low detection limit of 1.8×10(-11)M and obvious advantages such as small size, simple operation, and integrated circuit compatibility, providing a promising tool for pesticide analysis.

A micro-machined thin film electro-acoustic biosensor for detection of pesticide residuals *

Increasing awareness concerning food safety problems has been driving the search for simple and efficient biochemical analytical methods. In this paper, we develop a portable electro-acoustic biosensor based on a film bulk acoustic resonator for the detection of pesticide residues in agricultural products. A shear mode ZnO film bulk acoustic resonator with a micro-machining structure was fabricated as a mass-sensitive transducer for the real-time detection of antibody-antigen reactions in liquids. In order to obtain an ultra-low detection level, the artificial antigens were immobilized on the sensing surface of the resonator to employ a competitive format for the immunoassays. The competitive immunoreactions can be observed clearly through monitoring the frequency changes. The presence of pesticides was detected through the diminution of the frequency shift compared with the level without pesticides. The limit of detection for carbaryl (a widely used pesticide for vegetables and crops) is 2×10−10 M. The proposed device represents a potential alternative to the complex optical systems and electrochemical methods that are currently being used, and represents a significant opportunity in terms of simplicity of use and portability for on-site food safety testing.

Influence of the Crystal Texture on Raman Spectroscopy of the AlN Films Prepared by Pulse Laser Deposition

We investigate the Raman scattering of the AlN films prepared by pulse laser deposition. The Raman spectrum and the X-ray diffraction (XRD) patterns of the AlN films were compared to find out the influence of the crystal texture on the Raman scattering. The (high) and (TO) scattering modes were observed in Raman spectra. The results show that the orientation and the crystal quality of the AlN films have a great impact on these Raman scattering modes. The deterioration of (002) orientation and the appearance of other orientations in the XRD patterns lead to the weakening of the (high) mode and strengthening of the (TO) mode in the Raman spectrum. In addition, the (high) peak is broadened with the increasing of the width of the X-ray rocking curve. The broadening of the Raman peaks can be associated with degeneration in crystal quality. Furthermore, by combining the energy shift of (high) mode with the measured residual stress in the films, the Raman-stress factor of the AlN films prepared by pulse laser deposition is −4.45 cm−1/GPa for the (high) mode.

Thin-film-bulk-acoustic-resonator gas sensor for the detection of organophosphate vapor detection

A novel design of an organophosphate vapor sensor based on a thin film bulk acoustic resonator (TFBAR) is presented. The TFBAR device is consisted of an AlN piezoelectric stack and a Mo/AlN Bragg reflector. Poly (vinylidene fluoride) (PVDF) is coated on the surface of the piezoelectric stack as the special sensitive layer. The concentration of the target gas can be analyzed by measuring the resonant frequency. Adsorption of organophosphate compounds onto the PVDF can increase its mass, and the frequency proportionally goes down. The results show that the TFBAR sensor can yield a rapid, sensitive, reversible and reproducible response to dimethyl methyl phosphonate (a stimulant of sarin) vapor. The gas sensitivity of the proposed sensor is 220 kHz ppm−1 in the the vapor concentration range of 2–30 ppm. This study proves that using the chemical functionalized thin film bulk acoustic resonator to detect the trace hazardous gas is feasible.

MIXED-STATE ENTANGLEMENT IN A SINGLE-COOPER-PAIR BOX DETUNED WITH A COHERENT FIELD

A system composed of a single-Cooper-pair box irradiated by a single-mode quantized field has been considered. The entanglement relative to the mixedness μ and the detuning δ is investigated with negative partial transpose. It is found that in the case of initial mixed state, the entanglement is weakened, but increases as time evolves. For a detuned system, the entanglement is further suppressed but more stationary than that for a resonant system.