A streptavidin functionalized graphene oxide/Au nanoparticles composite for the construction of sensitive chemiluminescent immunosensor

In this work, a novel streptavidin functionalized graphene oxide/Au nanoparticles (streptavidin/GO/AuNPs) composite is prepared and for the first time used to construct sensitive chemiluminescent immunosensor for the detection of tumor marker. The streptavidin/GO/AuNPs composite and the immunosensor are characterized using scanning electron microscopy, static water contact angle measurement and electrochemical impedance spectroscopy. The biofunctionalized composite has large reactive surface area and excellent biocompatibility, thus the capture antibody can be efficiently immobilized on its surface based on the highly selective recognition of streptavidin to biotinylated antibody. Using α-fetoprotein (AFP) as a model, the proposed chemiluminescent immunosensor shows a wide linear range from 0.001 to 0.1 ng mL⁻¹ with an extremely low detection limit down to 0.61 pg mL⁻¹. The resulting AFP immunosensor shows high detection sensitivity, fast assay speed, acceptable detection and fabrication reproducibility, good specificity and stability. The assay results of serum samples with the proposed method are in an acceptable agreement with the reference values. This work provides a promising biofunctionalized nanostructure for sensitive biosensing applications.     

Energy transfer between CdS quantum dots and Au nanoparticles in photoelectrochemical detection

This work is the first report on the energy transfer between CdS quantum dots and Au nanoparticles for photoelectrochemical biosensing applications.     

Facile synthesis of polyaniline/TiO2/graphene oxide composite for high performance supercapacitors

The polyaniline/TiO₂/graphene oxide (PANI/TiO₂/GO) composite, as a novel supercapacitor material, is synthesized by in situ hydrolyzation of tetrabutyl titanate and polymerization of aniline monomer in the presence of graphene oxide. The morphology, composition and structure of the composites as-obtained are characterized by SEM, TEM, XRD and TGA. The electrochemical property and impedance of the composites are studied by cyclic voltammetry and Nyquist plot, respectively. The results show that the introduction of the GO and TiO₂ enhanced the electrode conductivity and stability, and then improved the supercapacitive behavior of PANI/TiO₂/GO composite. Significantly, the electrochemical measurement results show that the PANI/TiO₂/GO composite has a high specific capacitance (1020 F g⁻¹ at 2 mV s⁻¹, 430 F g⁻¹ at 1 A g⁻¹) and long cycle life (over 1000 times).     

Surface-treated TiO2 nanoparticles for dye-sensitized solar cells with remarkably enhanced performance

Dye-sensitized solar cells (DSSCs) were prepared by capitalizing on mesoporous P-25 TiO(2) nanoparticle film sensitized with N719 dyes. Subjecting TiO(2) nanoparticle films to TiCl(4) treatment, the device performance was improved. More importantly, O(2) plasma processing of TiO(2) film that was not previously TiCl(4)-treated resulted in a lower efficiency; by contrast, subsequent O(2) plasma exposure after TiCl(4) treatment markedly enhanced the power conversion efficiency, PCE, of DSSCs. Remarkably, with TiCl(4) and O(2) plasma treatments dye-sensitized TiO(2) nanoparticle solar cells produced with 21 μm thick TiO(2) film illuminated under 100 mW/cm(2) exhibited a PCE as high as 8.35%, twice of untreated cells of 3.86%.     

Raman and photoluminescence investigation of CdS/CdSe quantum dots on TiO2 nanoparticles with multi-walled carbon nanotubes and their application in solar cells

Raman spectroscopy and photoluminescence (PL) were used to investigate the improved short-circuit current density (J_SC) of CdS/CdSe quantum dot (QD)-sensitized solar cells with multi-walled carbon nanotubes (MWCNTs). Raman and PL experiments were carried out in order to explore the hot-electron and cold-electron injections, respectively. The experimental results showed that the concentration of MWCNTs influences the hot-electron and cold-electron injections from CdS/CdSe QDs to TiO₂ nanoparticles. Therefore, the improved J_SC in CdS/CdSe QD-sensitized solar cells can be explained as due to the better electron injections.     

A new photoelectrochemical aptasensor for the detection of thrombin based on functionalized graphene and CdSe nanoparticles multilayers

A photoelectrochemical sensing strategy for highly sensitive detection of thrombin was developed based on a layer-by-layer (LBL) assembly of functionalized graphene and CdSe nanoparticles.     

Directly assembled CdSe quantum dots on TiO2 in aqueous solution by adjusting pH value for quantum dot sensitized solar cells

We report an improved quantum dot sensitized solar cell (QDSSC) by loading mercaptopropionic acid (MPA)-capped CdSe QDs on TiO₂ film in aqueous solution. Under suitable pH value, a power conversion efficiency of 1.19% and an incident photon to current conversion efficiency of 26% for the QDSSC were obtained at AM1.5G irradiation. The improved performance of QDSSC is attributed to the large loading and good coverage of QDs on TiO₂ film with optimal pH value.     

Thiourea functionalized CdSe/CdS quantum dots as a fluorescent sensor for mercury ion detection

CdSe/CdS quantum dots(QDs) functionalized by thiourea(TU) were synthesized and used as a fluorescent sensor for mercury ion detection.The TU-functionalized QDs were prepared by bonding TU via electrostatic interaction to the core/shell CdSe/CdS QDs after capping with thioglycolic acid(TGA).It was observed that the fluorescence of the functionalized QDs was quenched upon the addition of Hg~(2+).The quantitative detection of Hg~(2+) with this fluorescent sensor could be conducted based on the linear relationship between the extent of quenching and the concentration of Hg~(2+) added in the range of1-300 μg L~(-1).A detection limit of 0.56 μg L~(-1) was achieved.The sensor showed superior selectivity for Hg~(2+) and was successfully applied to the determination of mercury in environmental samples with satisfactory results.     

Layered MoS2@graphene functionalized with nitrogen-doped graphene quantum dots as an enhanced electrochemical hydrogen evolution catalyst

Layered MoS₂@graphene functionalized with nitrogen-doped graphene quantum dots (MoS₂@NGQDs-GR) was obtained by one-pot hydrothermal method, as an enhanced electrochemical hydrogen evolution catalyst.     

Synthesis of new functionalized reduced graphene oxide quantum dot composite for high-performance NO2 gas sensor

Research on Chemical Intermediates - In this research, synthesis of a novel magnetic 2-naphthalenesulfonic acid-grafted reduced graphene oxide quantum dot (Fe3O4-rGOQD-naphthalene-2-SO3H) via a...     

Self-assembled reduced graphene oxide/sulfur composite encapsulated by polyaniline for enhanced electrochemistry performance

Reduced graphene oxide/sulfur/polyaniline (referred to RGO/S/PANI) composite was self-assembled through in situ synthesis and used to investigate the electrochemical properties of lithium/sulfur cells. The RGO/S/PANI composite possessed 809.3/801.9 mAh g^?1 of initial charge/discharge capacities, higher than 588.3/588.2 mAh g^?1 for reduced graphene oxide/sulfur (referred to RGO/S) and 681.4/669.9 mAh g^?1 for sulfur/polyaniline (referred to S/PANI) at similar conditions. The RGO/S/PANI composite obtained 400 mAh g^?1 at 2 C and good reversible capacities of 605.5 and 600.8 mAh g^?1 at 100th charge/discharge cycle at 0.1 C, in comparison with low electrochemical performance of RGO/S and S/PANI. The improved properties could be attributed to the collaboration of RGO and PANI. Co-generation of RGO and sulfur acted as seeds for their depositions, stimulated their uniform distributions, and restricted the agglomeration of sulfur particles in situ synthesis. Polyaniline coated RGO/S and stabilized the nanostructure of RGO/S/PANI in repeated charge/discharge cycles. In addition, RGO and PANI provided many electron channels to enhance sulfur conductivity and sufficient void space for sulfur swelling during charge/discharge cycles.     

TiO2 nanocrystals/graphene hybrids with enhanced Li-ion storage performance

TiO_2 nanocrystals/graphene hybrids(TiO_2-G) with ultrafine TiO_2 nanocrystals(~7 nm in size) conformally coated on ultrathin graphene nanosheets(~ 2 layers thick) were successfully prepared via a facile one-pot solvothermal route under mediated conditions.With the feature of large surface area,abundant mesopores and high thermal stability,the TiOi-G nanohybrids exhibited large reversible Li-ion storage capacity with excellent cycling stability(629 mAh·g~(-1) after 400 cycles at a current of 60 mA·g~(-1)) and good rate capability(184 mAh·g~(-1) at a current density of 3 A·g~(-1)) due to the synergetic effects and strong interactions between the components,showing great promise in applications for advanced energy storage devices.     

Potassium ion recognition by 15-crown-5 functionalized CdSe/ZnS quantum dots in H2O

Based on 15-crown-5 functionalized CdSe/ZnS quantum dots (QDs), we report a novel fluorogenic sensor to probe K+ ions in H2O; recognition of K+ can be achieved via the F?rster type of energy transfer between two different color QDs, so that [K+] of the order of 10(-6) M can be promptly detected.     

Capping nanoparticles with graphene quantum dots for enhanced thermoelectric performance

Graphene quantum dots (GQDs) are shown to serve as phase transfer agents to transfer various types of nanoparticles (NPs) from non-polar to polar solvents. Thorough characterization of the NPs proves complete native ligand exchange. Pellets of this GQD–NP composite show that the GQDs limit the crystal size during spark plasma sintering, yielding enhanced thermoelectric performance compared with NPs exchanged with inorganic ions. A photoluminescence study of the GQD–NP composite also suggests energy transfer from GQDs to NPs.     

Visible light photoelectrochemical sensor for ultrasensitive determination of dopamine based on synergistic effect of graphene quantum dots and TiO2 nanoparticles

We have demonstrated a facile approach for fabricating graphene quantum dots–TiO₂ (GQDs–TiO₂) nanocomposites by a simple physical adsorption method. Compared with pure GQDs and TiO₂ nanoparticles (NPs), the as-prepared GQDs–TiO₂ nanocomposites showed enhanced photoelectrochemical (PEC) signal under visible-light irradiation. The photocurrent of GQDs–TiO₂/GCE was nearly 30-fold and 12-fold enhancement than that of GQDs/GCE and TiO₂/GCE, respectively, which was attributed to the synergistic amplification between TiO₂ NPs and GQDs. More interestingly, the photocurrent of GQDs–TiO₂ nanocomposites was selectively sensitized by dopamine (DA), and enhanced with the increasing of DA concentration. Further, a new PEC methodology for ultrasensitive determination of DA was developed, which showed linearly enhanced photocurrent by increasing the DA concentration from 0.02 to 105 μM with a detection limit of 6.7 nM (S/N = 3) under optimized conditions. This strategy opens up a new avenue for the application of GQDs-based nanocomposites in the field of PEC sensing and monitoring.     

Preparation and photoelectrochemical performance of PbSe/BaTiO3/TiO2 composite film

By dipping-lifting in sol–gel solution and reducing process, the TiO₂ composite film on the glass plate was first prepared. Then, the PbSe/BaTiO₃/TiO₂ composite film was fabricated by interface reaction with BaTiO₃ and PbSe on the surface of TiO₂ composite film. The characterization results show that the uniform porous TiO₂ film is made up of the anatase crystal, and the PbSe/BaTiO₃/TiO₂ composite film is constructed by doping or depositing BaTiO₃ and PbSe nanoparticles on the surface of TiO₂ film. The photoelectrochemical measurement results indicate that the PbSe/BaTiO₃/TiO₂ composite film has an interesting photoelectrochemical conversion property.     

Enhancement of photovoltaic performance of polyaniline/graphene composite-based dye-sensitized solar cells by adding TiO2 nanoparticles

Polyaniline (PANi)-graphene composites and polyaniline-graphene/TiO₂ composites were prepared by ex-situ approach. Systematic investigation was carried out to explore photovoltaic (PV) properties of PANi-graphene and PANi-graphene/TiO₂ composite. The prepared composites were characterized using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Raman Spectroscopy and Ultraviolet–Visible (UV–Vis) Spectroscopy. The PV properties of dye-sensitized solar cells (DSSCs) prepared composites investigated by assembling materials in ITO/PANi-graphene/Al and ITO/PANi-graphene/TiO₂/Al architecture. Different PV parameters such as short circuit current, open circuit voltage, fill factor and power conversion efficiency were determined from the (Current-Voltage) IV characteristics of PV cell. The 15 wt% PANi loaded graphene composite based PV cell shows optimized power conversion efficiency of the order 6.47%. The main accomplishment of present work is that efficiency associated with 15 wt% PANi loaded graphene composite, improved further by addition of TiO₂ nanoparticles. The composite system between PANi-graphene/TiO₂ for 1 wt% of TiO₂ nanoparticles shows optimized power conversion efficiency of the order 8.63%.