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Wang R.,Chongqing University | Xu Y.,Chongqing University | Xu Y.,National Center for International Research of Micro Nano System and New Material Technology | Xu Y.,Key Laboratory of Fundamental Science of Micro Nano Device and System Technology for National Defense | And 2 more authors.
Analytical Methods | Year: 2015

In this study, a combination of carbon dots (CDs) and aptamers is proposed as a novel fluorescence probe for sensitive quantitative detection of Salmonella typhimurium. Carboxyl-modified CDs with better biocompatibility and monodispersity were prepared by a hydrothermal method using citric acid as carbon source. To ensure specificity, amino-modified aptamers were connected to the surface of CDs modified with carboxyl to form the carbon dot-aptamer complexes (CD-apt), which are of extremely high quantum yield (ca. 76%) and specificity. Salmonella typhimurium was taken as a representative sample for fluorescence detection, and incubation time and dosage of CD-apt were investigated. Under the optimized conditions, a linear relationship between concentration of Salmonella typhimurium and fluorescence intensity was obtained in the range of 103 to 105 cfu mL-1 using the equation I = 82.506:log:C - 203.17 with R2 = 0.9903, and the detection limit was down to 50 cfu mL-1 without any sample enrichment process. Significantly, the practicability of this method was validated by assaying Salmonella typhimurium in egg samples and tap water. The proposed method is promising for rapid and sensitive detection of other bacteria if suitable aptamers are chosen. This journal is © The Royal Society of Chemistry.


Wang R.,Chongqing University | Xu Y.,Chongqing University | Xu Y.,National Center for International Research of Micro Nano System and New Material Technology | Xu Y.,Key Laboratory of Fundamental Science of Micro Nano Device and System Technology for National Defense | And 4 more authors.
Analytical Methods | Year: 2014

CdSe/ZnS@SiO2-NH2 composite nanoparticles (FNPs) were proposed and used as fluorescent markers for bacteria detection. Salmonella typhimurium acted as representative sample in this paper. It was shown that hydrophobic CdSe/ZnS quantum dots (QDs) were incorporated into SiO2 spheres by using a self-modified reverse-microemulsion technique. FNPs could be successfully covalently conjugated with the bacteria by glutaraldehyde in a two-step strategy. A good linear relationship between the concentration of Salmonella typhimurium and fluorescence intensity was obtained in the range of 6.6 × 102 to 6.6 × 104 cfu mL-1, and the equation was I = 0.1331logC - 0.2017 with R2 = 0.9974. The detection limit was 3.3 × 102 cfu mL-1, and this method could be applied to other bacteria detection as well. In order to further reduce the detection limit and achieve better visual determination performance, an integrated dielectrophoresis (DEP) microfluidic chip and relative microsystem was established. The FNP-labeled bacteria could be enriched along the edges of interdigitated microelectrodes in the micro-channel by positive DEP and could be counted under the fluorescence microscope. This journal is © the Partner Organisations 2014.


Wang R.,Chongqing University | Ni Y.,Chongqing University | Xu Y.,Chongqing University | Xu Y.,National Center for International Research of Micro Nano System and New Material Technology | And 4 more authors.
Analytica Chimica Acta | Year: 2015

The new method presented in this article achieved the goal of capturing Salmonella typhimurium via immunoreaction and rapid in situ detection of the CdSe/ZnS quantum dots (QDs) labeled S. typhimurium by self-assembly light-emitting diode-induced fluorescence detection (LIF) microsystem on a specially designed multichannel microfluidic chip. CdSe/ZnS QDs were used as fluorescent markers improving detection sensitivity. The microfluidic chip developed in this study was composed of 12 sample channels, 3 mixing zones, and 6 immune reaction zones, which also acted as fluorescence detection zones. QDs-IgG-primary antibody complexes were generated by mixing CdSe/ZnS QDs conjugated secondary antibody (QDs-IgG) and S. typhimurium antibody (primary antibody) in mixing zones. Then, the complexes went into immune reaction zones to label previously captured S. typhimurium in the sandwich mode. The capture rate of S. typhimurium in each detection zone was up to 70%. The enriched QDs-labeled S. typhimurium was detected using a self-assembly LIF microsystem. A good linear relationship was obtained in the range from 3.7×10 to 3.7×105cfumL-1 using the equation I=0.1739 log (C)-0.1889 with R2=0.9907, and the detection limit was down to 37cfumL-1. The proposed method of online immunolabeling with QDs for in situ fluorescence detection on the designed multichannel microfluidic chip had been successfully used to detect S. typhimurium in pork sample, and it has shown potential advantages in practice. © 2014.


Yu H.,National Key Laboratory of Fundamental Science of Micro Nano Device and System Technology | Yu H.,National Center for International Research of Micro Nano System and New Material Technology | Yu H.,Chongqing University | Wen Z.,National Key Laboratory of Fundamental Science of Micro Nano Device and System Technology | And 5 more authors.
Chinese Journal of Sensors and Actuators | Year: 2010

In order to widen the frequency bandwidth of piezoelectric vibration based generator, the structure with multi-beams and single mass is designed. The simulation model of the piezoelectric vibration based generator with the structure of multi-beams and single mass is established. The relationship between the resonant frequency and structural parameters and the relationship between the output voltage and resonant frequency are analyzed. The experimental model of the generator with multi-beams and single mass structure is assembled. The experimental results shows that the designed generator can effectively convert the environmental vibration energy to electric energy with the frequency from 113 Hz to 155 Hz, the minimum output power is 37. 56 μW ,the maximum output power is 155.71 μW, and the frequency bandwidth of the generator is up to 42 Hz.


Gu W.-W.,National Key Laboratory of Fundamental Science of Micro Nano Device and System Technology | Gu W.-W.,National Center for International Research of Micro Nano System and New Material Technology | Gu W.-W.,Chongqing University | Wen Z.-Y.,National Key Laboratory of Fundamental Science of Micro Nano Device and System Technology | And 10 more authors.
Nami Jishu yu Jingmi Gongcheng/Nanotechnology and Precision Engineering | Year: 2010

A novel contactless conductivity detector with two electrodes integrated along the sidewalls of the ending separation channel of silicon-based electrophoresis microchip was presented in this paper, and factors influencing the response sensitivity of conductivity detection were discussed. Parameters of the detector were determined by MEMS analysis software and the equivalent circuit simulation, including electrode length of 550 μm, width of 15 μm, distance of 80 μm, thickness of insulation layer of 1 μm and conductivity detection frequency of 300 kHz. Silicon on insulator (SOI) was used in the fabrication process as the substrate to fabricate cross section micro channel and integrate conductivity detection electrodes. The technology of deep etching and isolation was used to isolate the detection electrodes from the micro channel, and the technology of ion diffusion was employed to fabricate tridimensional electrodes along the sidewalls of the ending separation channel, so that silicon-based electrophoresis microchip with integration of contactless conductivity detection electrodes was obtained. Under the excitation of sine wave with V pp of 10 V and the operation frequency of 300 kHz, concentration gradient experiment for Na + inorganic cation and electrophoresis separation detection for Na + and Li + hybrid inorganic cations were conducted. The results show that within the concentration range of Na + from 1×10 -9 mol/L to 1×10 -4 mol/L, the conductivity response signal increases with the increase of Na + concentration and the detection limit reaches 1×10 -9 mol/L. The resolution of electrophoresis separation for Na + and Li + hybrid inorganic cations reaches 2.0, indicating that baseline separation is achieved.

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