Zhou Xucheng

Bacteria counting method based on polyaniline/bacteria thin film

A simple and rapid bacteria counting method based on polyaniline (PANI)/bacteria thin film was proposed. Since the negative effects of immobilized bacteria on the deposition of PANI on glass carbon electrode (GCE), PANI/bacteria thin films containing decreased amount of PANI would be obtained when increasing the bacteria concentration. The prepared PANI/bacteria film was characterized with cyclic voltammetry (CV) technique to provide quantitative index for the determination of the bacteria count, and electrochemical impedance spectroscopy (EIS) was also performed to further investigate the difference in the PANI/bacteria films. Good linear relationship of the peak currents of the CVs and the log total count of bacteria (Bacillus subtilis) could be established using the equation Y=-30.413X+272.560 (R(2)=0.982) over the range of 5.3×10(4) to 5.3×10(8)CFUmL(-1), which also showed acceptable stability, reproducibility and switchable ability. The proposed method was feasible for simple and rapid counting of bacteria.

Characterization of colorimetric sensor arrays by a multi-spectral technique

A new method based on a multi-spectral technique was proposed to characterize the signal of colorimetric sensor arrays for gas detection. Firstly, the characteristic wavelengths, which are most relevant to the detected substance, were extracted from the hyperspectral information of the colorimetric sensor arrays. Then, narrowband filters with the corresponding central wavelengths were selected to isolate the effective signal of the sensor arrays. In this study, ammonia (NH3) was taken as an example to test the performance of the proposed multi-spectral method. Prediction of NH3 concentration based on the hyperspectral method and normal tri-color (R/G/B) method was also performed for comparison. Compared with the tri-color method, the correlation coefficient for the testing set (Rt) based on the multi-spectral method increased from 0.902 to 0.976, root mean squared error of prediction (RMSEP) decreased from 1.213 to 0.548, and residual predictive deviation for the testing set (RPDt) increased from 2.903 to 6.151, which means that the results were notably improved both in accuracy and stability. Furthermore, the multi-spectral method possesses the advantages of low cost, easy operation and greatly reduced data size. The proposed multi-spectral method could be used to characterize the signal of colorimetric sensor arrays for gas detection.

Micro-sensors based on hypha-templated coaxial microfibers

Biological templates show great potential in the fabrication of advanced materials since they are green, renewable and easy to obtain. Hyphae of Penicillium are demonstrated to be a versatile template for the fabrication of coaxial microfibers. Five kinds of nanomaterials, including ZnO, Fe3O4, Cu(OH)2, polypyrrole (PPy) and polyaniline (PANI), are coated on the hyphal surface without any modification. SEM, EDS, XRD and FT-IR were employed to confirm the morphology and chemical components of the prepared microfibers. The results showed that the fabricated nanomaterials were attached firmly on the hyphal surface to form an outside shell. An adsorption experiment showed that the cations could be attached on the hyphal surface with the help of related functional groups, which explained well the formation mechanism of the coaxial structure. Microsensors based on PANI/hypha, PPy/hypha and ZnO/hypha microfibers were fabricated and tested with TMA as the model gas. The prepared sensors showed a good linear response toward TMA with an R2 higher than 0.977, relative standard deviation for reproducibility measurement lower than 7.2%, and fast response–recovery speed, which demonstrate the applicability of the prepared coaxial microfibers.