Surface Plasmon Resonance Enhanced Scattering of Au Colloidal Nanoparticles

Suspended gold nanoparticles have been synthesized via electrochemical method. The strongest resonance scattering peak is at 485 nm, which results from the surface plasmon resonance. When the excited wavelength is at 242 nm (12.4 × 1014 Hz), there have been a 1/2 fraction frequency scattering peak at 485 nm (1/2 × 12.4 × 1014 Hz) and a 1/3 fraction frequency scattering peak at 726 nm (1/3 × 12.4 × 1014 Hz) displayed. Emission spectra with different particle diameters were compared, the intensity of scattering light increases with the particle size. The frequency-dependent scattering average cross section of small particle was calculated from Mie theory. The model calculation is in agreement with the experimental results.

Optical Nonlinearity of Surface Plasmon Resonance Emission from Au Colloidal Nanoparticles

Suspended gold nanoparticles have been synthesized via electrochemical method.Fluorescence excitation and emission spectra were obtained using a spectrofluorophotometer.With varying the excitation wavelength,an emission peak fixed at 485 nm has always been observed.We believe that this peak is attributed to the surface plasmon resonance.When the detection wavelength was fixed at 485 nm (0.619×10 15 Hz),a double frequency exciting peak at 242 nm(2×0.619×10 15 Hz), a 3/2 fraction frequency exciting peak at 330 nm (about 3/2×0.619×10 15 Hz)and a 3/4 fraction frequency exciting peak at 640 nm(3/4×0.619×10 15 Hz)display.The nonlinear exciting peak at 640 nm corresponds to the two-photon absorption.Therefore,as the excitation wavelength is at 320 and 640 nm respectively,single-photon and two-photon absorption induced surface plasmon resonance emission peaks were observed. These nonlinear surface plasmon resonance emission characters of Au colloidal nanoparticles make it possible to enhance the sensitivity of conventional surface plasmon resonance device.

Detection of Penicillin via Surface Plasmon Resonance Biosensor

A method of using Au colloid to capture the decomposed product of penicillin, penicillamine, on a surface plasmon resonance（SPR） biosensor for the quantitative determination of penicillin was developed. Based on the de-composition of penicillin to generate penicillamine and penilloaldehyde, a high sensitive biosensor for detecting penicillin was also developed. In our experiment, it was penicillamine rather than penicillin that has been measured. This is because penicillamine contains a functional group that makes it self-assembling on Au colloid to increase the molecular weight so as to improve the surface plasmon resonance signal. On a UV-Vis spectrophotometer, a high concentration of penicilliamine-Au complex was determined, indicating that penicillamine was already well combined with Au colloid. The method, using the combination of Au colloid with penicillamine, proved to detect penicillin.

Templated self-assembly of Au-TiO_2 binary nanoparticles-nanotubes

In this work, we developed a templated self-assembly approach to fabricate self-supporting Au/TiO2 binary nanoparticles-nanotubes （NPNTs） for the first time. The stable Au/TiO2 nanoparticles colloids were pre-synthesized and then deposited onto an AAO template, following by a mild calcination process. Au/TiO2 binary NPNTs can be achieved after removing the AAO template by NaOH solution. In addition, Au/TiO2 NPNTs with different thicknesses and size distributions could be achieved by tailoring the process parameters, such as the molar ratio of AuNPs to TiO2NPs, deposition modes and calcinations conditions. Therefore, these findings made controllable formation of Au/TiO2 NPNTs attractive for promising fabrication methodologies of metal/metal oxides NPNTs.

Highly sensitive potentiometric immunosensor for hepatitis B surface antigen diagnosis

A highly sensitive potentiometric immunosensor for the diagnoses of epidemic dis-eases has been developed by means of self-assembly to immobilize hepatitis B surface antibody(HBsAb)for the detection of hepatitis B surface antigen(HBsAg)as a model.At first,the Nafion containing-SO^(-)_(3)groups was immobilized on a platinum electrode surface to absorb the-NH^(+)_(3)groups of antibody molecules via the opposite-charged adsorption technique,in the meantime,hepatitis B surface antibodies were adsorbed onto the surface of Au nanoparticles,then hepatitis B surface antibodies and Au nanopartilces were entrapped into polyvinyl butyral on the surface of Nafion film.The modified procedure was further characterized by electrochemical impedance spectroscopy(EIS)and cyclic voltammetry(CV).The influence and factors influencing the per-formance of resulting immunosensor were studied in detail.The resulting immunosensor exhib-ited sigmoid curve with log HBsAg concentrations,high sensitivity,wide linear range from 26 to 1280 ng·mL^(-1)with a detection limit of 3.1 ng·mL^(-1),rapid potentiometric response(<3 min)and long-term stability(>4 months).Analytical results of clinical samples show that the developed immunoassay is comparable with the enzyme-linked immunosorbent assays(ELISAs)method,implying a promising alternative approach for detecting HBsAg in the clinical diagnosis.