Yanbo Cao

Sensitivity enhancement of SPR biosensor with silver mirror reaction on the Ag/Au film

Based on well-known silver mirror reaction the Ag film was formed on Au film modified by self-assembled monolayer (SAM) of 1,6-hexanedithiol (HDT). The sensitivity of the biosensor based on this Ag/Au film is enhanced compared to that based on Au film. When the surface plasmon resonance (SPR) biosensor based on this Ag/Au film was used to determine human IgG, the range of concentrations of human IgG that could be determined is 0.30-40.00 microg mL(-1). The lowest concentration (0.30 microg mL(-1)) that could be detected was about 8 times lower than that obtained by the biosensor without modification by Ag film (2.50 microg mL(-1)), which demonstrated that the biosensor based on Ag/Au film could make the resonant wavelength move to longer wavelength following with the sensitivity enhancement of the SPR biosensor.

Surface plasmon resonance biosensor based on water-soluble ZnO-Au nanocomposites

A wavelength modulation surface plasmon resonance biosensor based on ZnO-Au nanocomposites for the detection of human IgM was developed. Self-assembly technique has the advantages of flexibility, simplicity and the precise control of film component and was applied to the building of the sensor. The ZnO-Au nanocomposites are in a dumbbell-like shape and can be immobilized on the Au film through 1,6-hexanedithiol by covalent attachment. Meanwhile the activated ZnO nanocrystals can be used to connect protein. The biosensor based on ZnO-Au nanocomposites was used to detect human IgM. Some experimental conditions were examined and optimized. In the selected conditions, the modified biosensor exhibits a satisfactory response for human IgM in the concentration range of 0.30-20.00 microg mL(-1). However, the biosensor without ZnO-Au nanocomposites shows a response for human IgM in the concentration range of 1.25-20.00 microg mL(-1). Compared with the biosensor based on Au film, when the biosensor based on the ZnO-Au nanocomposites was applied, the sensitivity for determination of human IgM is significantly enhanced.

Surface plasmon resonance biosensor based on Au nanoparticle in titania sol-gel membrane.

A novel surface plasmon resonance (SPR) biosensor for the determination of human IgG was introduced. The biosensor was prepared with three layers of titania sol-gel membrane by vapor deposition. The colloid Au nanoparticle (AuNP) was immobilized in the second layer of titania membrane and the AuNP coupled with rabbit anti-human IgG was encapsulated in the third layer. The AuNP in the second layer of titania membrane was proved to be effective in the sensitivity enhancement of SPR biosensor. The lowest concentration that could be detected obtained by the biosensor with AuNP is about eight times lower than that obtained without AuNP. In addition, the titania sol-gel is a porous homogeneous material that permits analytes to access the encapsulated biomolecule and can provide a controlled environment for the study of biomolecular recognition. The titania sol-gel was also confirmed to be benefit for biomolecule to keep bioactivity, which could offer a good waterish microenvironment. As a result, the modified biosensor exhibits a satisfactory response for human IgG in the concentration range of 0.30-40.00 microg mL(-1) and shows favorable bioactivity for a long time.

Recent advances in microwave plasma torch atomic emission spectrometry

The development of an alternative excitation source, the microwave plasma torch (MPT) is historically reviewed. The unique features and shortcomings of the MPT as an excitation source for AES are outlined. To overcome the relatively severe matrix effects, desolvation, flow injection, on-line preseparation and preconcentration as well as on-line standard additions techniques have been adopted. An oxygen-sheathed Ar-MPT has been developed to alleviate the interferences caused by the strong nitrogen-related emission bands and this has also been shown to be valuable in reducing noise levels as well as improving the excitation capability. Some possible future developments are envisioned.

An inexpensive continuous-type ultrasonic nebulizer for atomic spectrometry

We developed an inexpensive continuous-type ultrasonic nebulizer for atomic spectrometry based on a domestic humidifier. With this nebulizer, the aerosol introduction rate is about 1.0 mL/min, much greater than that of pneumatic nebulizer. The long-term stability was also satisfactory because both the solution level and the coupling water temperature were held constant. The pumps controlled by a computer allow the nebulizer to work continuously. The results show that both the analytical performance and the cost were satisfactory.

Portable analyzer for rapid analysis of total protein, fat and lactose contents in raw milk measured by non-dispersive short-wave near-infrared spectrometry

A novel portable analyzer for raw milk quality control during the material purchase at dairy plants was developed, by which the percentages(mass fraction) of main components including total protein, fat, and lactose of an unhomogenized milk sample could be determinated in 1 min with the help of non-dispersive short-wave near-infrared (NDSWNIR) spectrometry in a wavelength range from 600 nm to 1100 nm and multivariate calibration. The analyzer was designed with a single-beam optical system, which comprised a temperature control module, a multi-channel narrow-band light source(16 wavelengths), a glass absorption cell with 15 mm sample thickness, a silicon photodiode detector, several compound lenses and a recorder module. A total of 80 raw milk samples were collected at a dairy farm twice a month for 4 months. The samples were scanned with a common UV-Vis-NIR spectrometer and analyzed according to China GB standard methods. The uninformative variables elimination(UVE) method was carried out on the spectrum data and the percentages of main components of all the samples to choose the peak emitting wavelength of each channel of the light source. Another 90 raw milk samples were collected from the same dairy farm thrice a month for 3 months. The samples were analyzed according to China GB standard methods and with the proposed analyzer. The percentages of the main components and the NDSWNIR absorption data of the samples were used for the construction and validation of the multivariate calibration model with partial least squares(PLS) method. The root-mean-square errors of prediction(RMSEP) of total protein, fat and lactose were 0.201, 0.172 and 0.247 and the coefficients of correlation(R) were 0.932, 0.981 and 0.933, respectively.

Study of using a Nafion dryer as a desolvation device for MPT-AES

In this paper a novel desolvation device, Nafion dryer has been introduced into an MPT-AES, and its operating parameters, such as heating temperature, purge gas flow rate and peristaltic pump rotation speed, have been optimized. A comparison between a condensation system and the Nafion dryer system was carried out and the results indicated that the Nafion dryer system has good performance for desolvation.

Evaluation of Improved Ultrasonic Nebulizer for Miniature Simultaneous Microwave Plasma Torch Spectrometer

A new automatic sample solution introduction system for miniature simultaneous microwave plasma torch(MPT) atomic emission spectrometer was developed. The operating parameters were optimized. The detection limits of the spectrometer with an ultrasonic nebulizer for Ag, Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Sr, and V are 5—10 times lower than those obtained with a pneumatic nebulizer and are also lower than those obtained by a Model JX-1010 MPT spectrometer. Two practical samples were analyzed to test the reliability and sensitivity of the system.

Study of Spectral Character of Alkali Metals Using Microwave Plasma Torch Simultaneous Spectrometer

Abstract A microwave plasma torch (MPT) simultaneous spectrometer was used to study the spectral character and the matrix effect on alkali metal ions in solution. The main parameters were optimized. The microwave forward power was 100 W. The argon flow rate that was used to sustain the Ar-MPT included the flow rate of carrier gas and the flow rate of support gas, which were 0.8 and 1.0 L/min, respectively. The HC1 concentration in the solution was 0.02 mol/L. The observation height was 9.0 mm. The detection limits of Li, Na, K, Rb, and Cs were 0.0003, 0.0004, 0.009, 0.07 and 2.4 mg/L, respectively, and the results obtained by the Ar-MPT were compared with those obtained by argon inductively coupled plasma(Ar-ICP) and argon microwave induced plasma(Ar-MIP). The interference effects of several matrix elements were also studied.