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Objective To develop a method combining surface-enhanced Raman scattering (SERS) spectrum and electrostatic adsorption for detecting circulating tumor cells. Methods Graphene oxide was non-covalently functionalized by poly(sodium-p-styrenesulfonate) (PSS), and graphene oxide/gold nanorod (GO/GNR) hybrids were in situ synthesized via gold seeding growth approach. Then, GO/GNR hybrids were non-covalently functionalized by poly dimethyl diallyl ammonium chloride (PDDAC) to make the surface of GO/GNR positively charged. GO/GNR hybrids would target the tumor cells by electrostatic interaction. SERS technology was used to detect the composites of GO/GNR-tumor cells. The blood samples of healthy volunteers were collected, and the tumor cells of different densities were added to the blood samples to make simulated blood samples. The tumor cells in simulated blood samples were detected using the above methods. Results Positively charged GO/GNR hybrids could efficiently target the tumor cells. SERS spectroscopy could detect tumor cells within 50 to 10 000 cells. However, white blood cells might interfere the detection of tumor cells. Conclusion GO/GNR hybrids may serve as SERS probes for detection of circulating tumor cells via Raman spectroscopy.
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Super hydrophobic interface modified with silver nanoparticles was fabricated for the detection of pesticide residues.By using a chemical reduction method,silver nanoparticles were deposited on the substrate surfaces with different microscopic pore structures.Two kinds of composite substrates,including regular stainless steel mesh and cellulose polyester film,were used.The pre-treatment of the substrate with fluoridated reagents was used to form a super hydrophobic interface,which made the target molecules on the surface concentrate effectively.The surface with the cellulose polyester substrate was used to detect Rhodamine 6G (R 6G) effectively with surface enhanced Raman scattering (SERS) technique.The results showed that the detection hmit was 10-16 mol/L.In addition,the surfaces based on the stainless steel mesh and cellulose polyester substrate were used to detect trichlorfon pesticide with detection limits of 1 × 10-15 mol/L and 1 × 10-16 mol/L,respectively.
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The facile and efficient synthetic route for Ag dendritic nanostructures on Indium tin oxide ( ITO) via electrodeposition was reported. The results showed that the Raman intensities of rhodamine 6G ( R6G) decreased with decreasing the loading concentration, and even at a low concentration of 10-10 mol/L, the signatures of R6G in Raman spectrum were still clearly observed. It indicated that the Ag dendritic nanostructures exhibited high surface-enhanced Raman scattering ( SERS) sensitivity. Moreover, the relative standard deviation ( RSD ) of band at 610 cm-1 was calculated to be 12 . 1%, 12 . 0%, 11 . 7%, 10 . 9%, 13. 2% and 14. 3%, respectively, corresponding with the concentration of R6G from 10-5 mol/L to 10-10 mol/L, which revealed that the Ag dendritic nanostructures could provide abundant hot spots and exhibited excellent reproducibility. In addition, the SERS spectrum of 3-mercaptopropionic acid (3MPA) also could be detected when its concentration was 10-5 mol/L. This method offers an easy and low-cost way to prepare Ag dendritic substrates and makes SERS detection more practicable.
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A simple and efficient method for fabricating a novel surface-enhanced Raman scattering ( SERS) substrate with good reproducibility and high SERS activity was reported. Cu2 O was prepared by mixing CuCl2 ·2H2 O with ascorbic acid, which was then used as the templates for depositing of gold nanoparticles ( AuNPs) on their surfaces, forming Cu2 O@ Au with heterostructures. Transmission electron microscopy, scanning electron microscopy and X-ray diffraction observation revealed that Cu2 O had polyhedral structure and smooth surface, and AuNPs were closely deposited on the surface of Cu2 O. It was used as SERS substrate for detection of Rhodamine B with linear detection range of 1 × 10-2-5 × 10-6 mol/L, and detection limit of 3 ×10-7 mol/L. Cu2 O@Au showed good chemical stability, remained stable in acid, PBS and river samples, and could be used in the SERS detection of target in water sample.
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Gold nanochannels were prepared using Al2 O3 nanotubules membrane as the carrier and modified with chitosan by a classical N-(3-dimethylaminopropyl)-N-ethyl carbodiimide ( EDC)/N-hydroxysuccinimide ( NHS ) coupling reaction. The nanochannels were characterized by field emission scanning electron microscopy ( FESEM) , cyclic voltammetry and AC impedance method. The Au nanochannels modified with chitosan showed a chiral environment and can be used to separate histidine enantiomer. The effects of pore size and solution pH on the separation efficiency of histidine were investigated. To increase the detection sensitivity of D-, L-histidine, Ag nanoparticles were used to enhance the surface enhanced Raman scattering ( SERS) activity. The results showed that the chitosan-modified gold nanochannels can be used to separate chiral histidine based on this unique selective nanochannel membrane. L-Histidine and D-histidine were respectively detected by SERS at wavelengths of 1000 and 1590 cm-1 . The results showed that L-histidine and D-histidine were separated well in the mixture containing 200 μL of histidine, 100 μL of colloidal Ag and 100 μL of 80 mmol/L NaCl ( pH=7 . 59 ) with a separation efficiency of 4 . 91 .
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Objective To prepare self-assembled thiolated chitosan derivatives gold nanoparticles (CS-GNRs) and carry out the feature tests.Methods CS-GNRs was prepared by chitosan derivatives and GNRs through strong metal sulfur chemical bond between thiols and gold on GNRs surface.Morphology features was tested by transmission electron microscope,dynamic light scattering was adopted to observe the size of nanoparticles.Ultraviolet-visible spectrophotometer was used to detect the optical properties and the property change.Meanwhile,the surface-enhanced Raman scattering (SERS) activity of CS-GNRs was investigated by using crystal violet (CV) as a probe molecular.Results CS-GNRs were in good shape,uniform particle size and good dispersion.The SERS of CV was enhanced,and the enhancement factor of CV adsorbed on CS-GNRs was up to 2×103.Conclusions The nanoparticles have potential application in molecular detection and Raman spectra detection.
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A rapid detection method of active pharmaceutical ingredients( API) in weak API signal drugs by surface enhanced Raman scattering ( SERS) technology combined with paper substrate was established in this work. By soaking the filter paper in silver nanoparticles solution ( Ag NPs) to synthesize Ag NPs-paper as the substrate, and then the sample solution was dropping on the substrate with SERS detection. On the basis of strengthen ability of Ag NPs-paper, result of SERS detection and optimal preparation conditions, the fast identification method of weak API signal drugs was established. In this case, the SERS spectra of weak API signal drugs and their standards SERS spectra were obtained, where the correlation coefficient of weak API signal drug SERS spectra and its standard was more than 0. 9. The result showed that by this method, the low content API in weak API signal drugs could be well investigated, and the deficiencies of the normal Raman spectroscopy efficiently was also overcome. In conclusion, the synthesize method of Ag NPs-paper was simple, and the strengthen effect of this Ag NPs-paper on the intensity was obviously observed. Paper substrate-SERS method was simple, rapid and sensitive, and could be used to detect weak API signal drugs, presenting broad application prospects in the rapid detection of weak API signal drugs.
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A rapid, sensitive, label-free and separation-free analytical method for determination of melamine ( MA) was developed based on surface enhanced Raman scattering ( SERS ) effect of gold nanoparticles. Through tri-sodium citrate reduction method, gold nanoparticles with average diameter of 30 nm were obtained. The melamine detection platform was constructed after self-assembling 4-mercapto phenylboronic acid (4-MPBA) on the surface of gold nanoparticles through Au S covalent bond. When MA existed in solution, 4-MPBA functionalized gold nanoparticles would aggregate because of strong hydrogen bond interaction between MA and 4-MPBA. Moreover, following increase of the concentration of MA, gold nanoparticles would aggregate more intensively and form more hot spots. As a result, Raman signal of 4-MPBA and MA was enhanced greatly. The characteristic Raman peaks of 4-MPBA and MA respectively located at 1076 cm-1 and 715 cm-1 . Hence, the qualitative and quantitative detection for MA were realized based on the ratio value of I715 cm-1 to I1076 cm-1 . The linear range of MA detection was 0 . 1 μmol/L-1. 5 μmol/L. The limit of detection (LOD) reached 0. 02 μmol/L in terms of three times signal to noise.