The Experts below are selected from a list of 51858 Experts worldwide ranked by ideXlab platform
Xiaoqi Fu - One of the best experts on this subject based on the ideXlab platform.
-
excitation profile of surface enhanced raman scattering in graphene metal nanoparticle based derivatives
Nanoscale, 2010Co-Authors: Xiaoqi Fu, Xin Wang, Stephen J Obrien, John R LombardiAbstract:Understanding energy transfer mechanisms in graphene derivatives is strongly motivated by the unusually interesting electronic properties of graphene, which can provide a template for the creation of novel nanostructured derivatives. From a synthetic point of view, it is highly attractive to envision being able to synthesize pristine graphene from precursors such as graphene oxide (GO). While this goal may be challenging over large length-scales, it is possible to generate regions of graphene at the nanoscale, confirmed by Raman spectroscopy or other methods. We describe an in situ method of nucleating gold or palladium nanoparticles in the presence of ethylene glycol as a reducing agent, while simultaneously reducing GO to graphene. The Au nanoparticles aid in spectroscopic characterization by both Quenching Fluorescence, allowing the graphene D and G bands to be quantified, and yielding a surface enhancement of about two orders of magnitude. We observe the excitation profile (488–785 nm) of the surface enhanced Raman spectrum (SERS) of graphene with Au nanoparticles adsorbed on the surface. Both the D and G bands display a resonance at approximately 593 nm (2.09 eV). This resonance may be interpreted as a combination of the plasmon resonance at 548 nm and a likely contribution from charge transfer as well. In addition, we observe a stiffening of the G band compared with that of graphene. The mechanism of the SERS, whether plasmonic or charge transfer-based, enables insight into the electronic pathways available to the graphene–nanoparticle system. We discuss our results in the context of several existing studies of graphene-based nanostructure derivatives.
John R Lombardi - One of the best experts on this subject based on the ideXlab platform.
-
excitation profile of surface enhanced raman scattering in graphene metal nanoparticle based derivatives
Nanoscale, 2010Co-Authors: Xiaoqi Fu, Xin Wang, Stephen J Obrien, John R LombardiAbstract:Understanding energy transfer mechanisms in graphene derivatives is strongly motivated by the unusually interesting electronic properties of graphene, which can provide a template for the creation of novel nanostructured derivatives. From a synthetic point of view, it is highly attractive to envision being able to synthesize pristine graphene from precursors such as graphene oxide (GO). While this goal may be challenging over large length-scales, it is possible to generate regions of graphene at the nanoscale, confirmed by Raman spectroscopy or other methods. We describe an in situ method of nucleating gold or palladium nanoparticles in the presence of ethylene glycol as a reducing agent, while simultaneously reducing GO to graphene. The Au nanoparticles aid in spectroscopic characterization by both Quenching Fluorescence, allowing the graphene D and G bands to be quantified, and yielding a surface enhancement of about two orders of magnitude. We observe the excitation profile (488–785 nm) of the surface enhanced Raman spectrum (SERS) of graphene with Au nanoparticles adsorbed on the surface. Both the D and G bands display a resonance at approximately 593 nm (2.09 eV). This resonance may be interpreted as a combination of the plasmon resonance at 548 nm and a likely contribution from charge transfer as well. In addition, we observe a stiffening of the G band compared with that of graphene. The mechanism of the SERS, whether plasmonic or charge transfer-based, enables insight into the electronic pathways available to the graphene–nanoparticle system. We discuss our results in the context of several existing studies of graphene-based nanostructure derivatives.
Maryam Shanehsaz - One of the best experts on this subject based on the ideXlab platform.
-
Quantum dot/polyvinyl alcohol composite nanofibers membrane as highly sensitive Fluorescence Quenching-based sensors
Fibers and Polymers, 2014Co-Authors: Matin Mahmoudifard, Ahmad Mousavi Shoushtari, Maryam ShanehsazAbstract:Nanofibrous membranes are intensively applied to fabricate advanced intelligent devices like highly sensitive sensors due to their flexibility, high porosity, high surface area and good mechanical and chemical stability. In this work, fluorescent cadmium telluride (CdTe) quantum dots (Q.Ds) were synthesized and then uniformly embedded in poly vinyl alcohol (PVA) nanofibers by electrospinning technique to serve as reversible Quenching Fluorescence-based sensor to detect the traces of benzene, toluene and xylene vapors selectively at room temperature. Fluorescence analysis suggested that Q.Ds preserve their original fluorescent property in solid nanofiber as if they were in solution. Scanning electron microscopy images showed the uniform diameter of nanofibers. In addition, Fluorescence and transmission electron microscopy (TEM) measurements confirmed the uniform distribution of the Q.Ds into nanofibers structures. The main mechanism of Quenching based sensor was designated as electron transfer from thiogalycolic acid (TGA) — capped Q.D surface to target volatile organic compounds (VOC’s) vapors. Fabricated sensor showed selectively sensing upon trace of different target vapors due to the difference in the electronegativity of various VOC’s molecules. For example exposure to more electron withdrawing toluene molecules induces severe Quenching effect on Fluorescence intensity of Q.D (about 25 %) over xylene exposure. Moreover, it was observed that reducing the diameter of nanofibers enhanced the sensitivity of sensor.
-
Quantum dot/polyvinyl alcohol composite nanofibers membrane as highly sensitive Fluorescence Quenching-based sensors
Fibers and Polymers, 2014Co-Authors: Matin Mahmoudifard, Ahmad Mousavi Shoushtari, Maryam ShanehsazAbstract:Nanofibrous membranes are intensively applied to fabricate advanced intelligent devices like highly sensitive sensors due to their flexibility, high porosity, high surface area and good mechanical and chemical stability. In this work, fluorescent cadmium telluride (CdTe) quantum dots (Q.Ds) were synthesized and then uniformly embedded in poly vinyl alcohol (PVA) nanofibers by electrospinning technique to serve as reversible Quenching Fluorescence-based sensor to detect the traces of benzene, toluene and xylene vapors selectively at room temperature. Fluorescence analysis suggested that Q.Ds preserve their original fluorescent property in solid nanofiber as if they were in solution. Scanning electron microscopy images showed the uniform diameter of nanofibers. In addition, Fluorescence and transmission electron microscopy (TEM) measurements confirmed the uniform distribution of the Q.Ds into nanofibers structures. The main mechanism of Quenching based sensor was designated as electron transfer from thiogalycolic acid (TGA) — capped Q.D surface to target volatile organic compounds (VOC’s) vapors. Fabricated sensor showed selectively sensing upon trace of different target vapors due to the difference in the electronegativity of various VOC’s molecules. For example exposure to more electron withdrawing toluene molecules induces severe Quenching effect on Fluorescence intensity of Q.D (about 25 %) over xylene exposure. Moreover, it was observed that reducing the diameter of nanofibers enhanced the sensitivity of sensor.
Erkang Wang - One of the best experts on this subject based on the ideXlab platform.
-
pvp coated graphene oxide for selective determination of ochratoxin a via Quenching Fluorescence of free aptamer
Biosensors and Bioelectronics, 2011Co-Authors: Linfeng Sheng, Jiangtao Ren, Yuqing Miao, Jiahai Wang, Erkang WangAbstract:Abstract In this paper, we developed a simple method to detect fungi toxin (ochratoxin A) produced by Aspergillus Ochraceus and Penicillium verrucosum m, utilizing graphene oxide as quencher which can quench the Fluorescence of FAM (carboxyfluorescein) attached to toxin-specific aptamer. By optimizing the experimental conditions, we obtained the detection limit of our sensing platform based on bare graphene oxide to be 1.9 μM with a linear detection range from 2 μM to 35 μM. Selectivity of this sensing platform has been carefully investigated; the results showed that this sensor specifically responded to ochratoxin A without interference from other structure analogues (N-acetyl- l -phenylalanine and warfarin) and with only limited interference from ochratoxin B. Experimental data showed that ochratoxin A as well as other structure analogues could adsorb onto the graphene oxide. As compared to the non-protected graphene oxide based biosensor, PVP-protected graphene oxide reveals much lower detection limit (21.8 nM) by two orders of magnitude under the optimized ratio of graphene oxide to PVP concentration. This sensor has also been challenged by testing 1% red wine containing buffer solution spiked with a series of concentration of ochratoxin A.
Matin Mahmoudifard - One of the best experts on this subject based on the ideXlab platform.
-
Quantum dot/polyvinyl alcohol composite nanofibers membrane as highly sensitive Fluorescence Quenching-based sensors
Fibers and Polymers, 2014Co-Authors: Matin Mahmoudifard, Ahmad Mousavi Shoushtari, Maryam ShanehsazAbstract:Nanofibrous membranes are intensively applied to fabricate advanced intelligent devices like highly sensitive sensors due to their flexibility, high porosity, high surface area and good mechanical and chemical stability. In this work, fluorescent cadmium telluride (CdTe) quantum dots (Q.Ds) were synthesized and then uniformly embedded in poly vinyl alcohol (PVA) nanofibers by electrospinning technique to serve as reversible Quenching Fluorescence-based sensor to detect the traces of benzene, toluene and xylene vapors selectively at room temperature. Fluorescence analysis suggested that Q.Ds preserve their original fluorescent property in solid nanofiber as if they were in solution. Scanning electron microscopy images showed the uniform diameter of nanofibers. In addition, Fluorescence and transmission electron microscopy (TEM) measurements confirmed the uniform distribution of the Q.Ds into nanofibers structures. The main mechanism of Quenching based sensor was designated as electron transfer from thiogalycolic acid (TGA) — capped Q.D surface to target volatile organic compounds (VOC’s) vapors. Fabricated sensor showed selectively sensing upon trace of different target vapors due to the difference in the electronegativity of various VOC’s molecules. For example exposure to more electron withdrawing toluene molecules induces severe Quenching effect on Fluorescence intensity of Q.D (about 25 %) over xylene exposure. Moreover, it was observed that reducing the diameter of nanofibers enhanced the sensitivity of sensor.
-
Quantum dot/polyvinyl alcohol composite nanofibers membrane as highly sensitive Fluorescence Quenching-based sensors
Fibers and Polymers, 2014Co-Authors: Matin Mahmoudifard, Ahmad Mousavi Shoushtari, Maryam ShanehsazAbstract:Nanofibrous membranes are intensively applied to fabricate advanced intelligent devices like highly sensitive sensors due to their flexibility, high porosity, high surface area and good mechanical and chemical stability. In this work, fluorescent cadmium telluride (CdTe) quantum dots (Q.Ds) were synthesized and then uniformly embedded in poly vinyl alcohol (PVA) nanofibers by electrospinning technique to serve as reversible Quenching Fluorescence-based sensor to detect the traces of benzene, toluene and xylene vapors selectively at room temperature. Fluorescence analysis suggested that Q.Ds preserve their original fluorescent property in solid nanofiber as if they were in solution. Scanning electron microscopy images showed the uniform diameter of nanofibers. In addition, Fluorescence and transmission electron microscopy (TEM) measurements confirmed the uniform distribution of the Q.Ds into nanofibers structures. The main mechanism of Quenching based sensor was designated as electron transfer from thiogalycolic acid (TGA) — capped Q.D surface to target volatile organic compounds (VOC’s) vapors. Fabricated sensor showed selectively sensing upon trace of different target vapors due to the difference in the electronegativity of various VOC’s molecules. For example exposure to more electron withdrawing toluene molecules induces severe Quenching effect on Fluorescence intensity of Q.D (about 25 %) over xylene exposure. Moreover, it was observed that reducing the diameter of nanofibers enhanced the sensitivity of sensor.
