[Show abstract][Hide abstract] ABSTRACT: Cyclodextrin (CD) capped CdTe quantum dots (QDs) were prepared with uniform dimension (average diameter ∼5 nm) and high quantum yield (ca. 65%). By taking advantage of the inclusion complexation of CD, β-CD-CdTe QDs exhibited strong fluorescence quenching in a linear relationship with the concentration of o-, m- and p-nitrophenol in the range of 20-100 μM. The detection limit reached 0.05 μM for o-/p-nitrophenol and 0.3 μM for m-nitrophenol. The fluorescence decay study revealed the stabilization effect of CD covering on CdTe QDs and fine-tuning of the fluorescence for selective ultrasensitive detection of nitrophenol isomers.
[Show abstract][Hide abstract] ABSTRACT: Flexible energy storage systems have recently attracted great interest for portable electronic devices. The functionalization of graphene provides vast platform in tailoring its nanostructure and properties for energy storage via facile processing. Here, we first demonstrate the development of chemically bonded graphene oxide and bacterial cellulose hybrid composite coated with polypyrrole for robust and high-efficiency supercapacitor electrodes. The as-prepared composites exhibited a highest electrical conductivity (1320 S m-1) and the largest volumetric capacitance (278 F cm-3) ever shown by carbon-based electrodes, along with 95.2% retention of 556 F g-1 gravimetric capacitance over 5000 recycling tests in asymmetric supercapacitors. Impressively, the hybrid electrode contributed a 492 F g-1 gravimetric capacitance and 93.5% retention over 2000 recycling in symmetric supercapacitors. The nanostructure and composition of the composites were found to play a crucial role for the performance of these three-dimensional, chemically bonded hybrid composite electrodes.
Chemistry of Materials 09/2015; 27(20):150930173019006. DOI:10.1021/acs.chemmater.5b03060 · 8.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report the transformation of hydrophilic graphene oxide (GO) sheets into superhydrophobic nanomaterial by direct esterification with epoxy-functionalized polyhedral oligomeric silsesquioxane (ePOSS). The covalently functionalized GO-ePOSS composite shows superhydrophobicity with a water/air contact angle of similar to 145 degrees. The highest dispersion limits for GO in selected organic solvents are obtained in the literature. The dispersion of GO-ePOSS can be extended to solvents with Hansen solubility parameters as low as 3.4. Efficient oil-water separation is also demonstrated by using a GO-ePOSS membrane.
[Show abstract][Hide abstract] ABSTRACT: The graphene-chitosan composite film modified glassy carbon electrode (GR-CS/GCE) was prepared for the simultaneous detection of p-nitrophenol (p-NP) and o-nitrophenol (o-NP). GR-CS/GCE showed good electrocatalytic activity for the reduction of p-NP and o-NP. Under the optimized detection conditions, p-NP exhibited a linear detection range of 0.1?140 μM with the detection limit (S/N = 3) of 0.09 μM at GR-CS/GCE, while 1?240 μM for o-NP with a detection limit of 0.1 μM. The GR-CS demonstrated as a promising sensor material for the simultaneous detection of nitrophenol isomers.
Journal of The Electrochemical Society 01/2015; 162(10):B269-B274. DOI:10.1149/2.0811510jes · 3.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The direct access to 4,8-functionalized benzo[1,2-b:4,5-b′]difurans (BDFs) is developed. By fine-tuning the energy levels with different 4,8-functionalities or incorporating with electron-accepting units, BDFs show great potential as organic electronic materials, as demonstrated with 4.61% power conversion efficiency for polymer solar cells.
[Show abstract][Hide abstract] ABSTRACT: We demonstrated herein the facile synthesis of triisopropylsilylethynyl (TIPS) functionalized benzo[1,2-b:4,5-b']dithiophene (BDT). Three new TIPSBDT-based donor-acceptor alternating copolymers were further developed by Pd-catalyzed Stille coupling. The effect of accepting unit structure on the optical, electrochemical and energy levels of the polymer was studied. The positive impact of PFN layer, high-boiling solvents processing, polar solvent treatment and solvent annealing on the performance of polymer:PC71BM bulk heterojuction solar cells was revealed. The best devices delivered a power conversion efficiency of 5.46% when blend films processed using o-dichlorobenzene with 3 vol% DIO and treated with the optimization of THF annealing and insertion of PFN layer. The device performance was correlated with the morphology evolution of blend films processed with solvent choice, methanol treatment and THF annealing.
[Show abstract][Hide abstract] ABSTRACT: Electrode materials with a three-dimensional (3D) network structure and high-conductivity are crucial for the development of robust high-performance supercapacitors. Herein, a facile method has developed for the covalent intercalation of graphene oxide (GO) with bacterial cellulose (BC) fibers via one-step esterification to construct a 3D cross-linked structural scalffords. The as-prepared composite exhibits a tensile strength of 18.48 MPa and an elongation at break of 24%. With an outstanding electrical conductivity of 171 S m-1, the composite electrode demonstrates a good mass-specific capacitance of 160 F g-1 at 0.4 A g-1 current density. Robust supercapacitor is demonstrated with an outstanding capacitance retention of 90.3% over 2000 recycles. The impressive mechanical and electrochemical properties of covalently intercalated BC/GO composite may open new avenue in developing cross-linked GO nanocomposites for stretchable electronics. This is the first report on the preparation of covalent intercalating BC/GO composite for robust supercapacitor application.
[Show abstract][Hide abstract] ABSTRACT: A two-dimensional (2D) low bandgap polymer (PDTS-Ph-TTz) based on dithieno[3,2-b:2’,3’-d]silole (DTS) with phenyl substitution on bridging silicon atom and thiazolo[5,4-d]thiazole (TTz) was designed and synthesized for photovoltaic application. The impact of conjugated side chains on the optical, electrochemical and energy levels of the polymer was studied. The phenyl substituted DTS polymer exhibited 0.16 eV downs-shifted highest occupied molecular orbital (HOMO) energy level and ca. 0.1 eV narrowed bandgap in comparison to the corresponding polymers with alkyl substitution on silicon bridge. The influence of blend weight ratio, PFN layer, mixed solvent, THF exposure and polar solvent treatment and thermal annealing on the performance of PDTS-Ph-TTz:PC71BM devices was studied. PDTS-Ph-TTz:PC71BM (1:1, weight ratio) devices delivered the highest power conversion efficiency of 2.14% by using PFN layer and THF annealing. Thermal annealing was found to exert negative effect on the device performance. The morphology evolution of blend films processed with different solvents explained the difference in device performance. The results indicate the phenyl substitution is an effective way to tune the HOMO and bandgap of polymer donors for enhanced photovoltaic performance with the as-demonstrated 2D-conjugated DTS structure.
[Show abstract][Hide abstract] ABSTRACT: Eight single-isomer ammonium-β-cyclodextrin derivatives with different side chains were successfully developed as chiral selectors for the chiral separation of selected racemates in capillary electrophoresis. The number of substituted groups at N-atom as well as the alkyl chain length greatly influenced the chiral separation. With the numbers of hydroxylalkyl groups at N-atom growing, the aqueous solubility of resolving agents were distinctly decreased and chiral separation ability was also significantly reduced. The apparent complex stability constants between CDs and analytes were further determined. The best enantioseparations of hydroxyl acids was achieved with the use of mono-6A-(3-hydroxypropyl)-1-ammonium-β-cyclodextrin chloride and mono-6A-(3-methoxypropyl)-1-ammonium-β-cyclodextrin chloride. The nuclear magnetic resonance experiments were carried out using them with mandelic acid as guest molecules, revealing the inclusion pattern as well as electrostatic interactions and hydrogen bonding interactions as additional chiral driving force. The contribution of potential interaction sites in the sidearm could enhance the enantioseparations.This article is protected by copyright. All rights reserved
[Show abstract][Hide abstract] ABSTRACT: Novel AC regioisomer cationic cyclodextrins have been successfully prepared with azide/alkylne click chemistry CDs. The clicked CDs were explored for the enantioseparation of acidic racemates in capillary electrophoresis.
[Show abstract][Hide abstract] ABSTRACT: The nanocomposite (denoted as GR-AuNPs-CD-CS) of graphene (GR), gold nanoparticles (AuNPs), chitosan (CS) and β-cyclodextrin (β-CD) was prepared to modify a glassy carbon electrode. The as-modified electrode was explored for the ultrasensitive detection of dopamine (DA) and uric acid (UA). The modified electrode demonstrated linearly increased current response in the concentration range of 0.1–120 µm for DA and 0.05–70 µm for UA, with so far the best detection limit for DA and UA. Good stability and repeatability were further demonstrated for the as-made sensor.
[Show abstract][Hide abstract] ABSTRACT: A general methodology has been proposed for the straightforward access to 4,8-functionalized benzo[1,2-b:4,5-b′]dithiophenes (BDTs) via Pd mediated coupling reactions including Suzuki–Sonogashira coupling and carbon–sulfur bond formation reactions. This versatile platform can be used to construct a library of BDT core centred conjugated systems, featuring large fused-ring structure and good charge mobility, where a hole mobility of 0.061 cm2 V−1 s−1 is demonstrated. With the energy level fine-tuned with functionalization, the charge transporting BDTs show great potential for donor–acceptor polymers.
[Show abstract][Hide abstract] ABSTRACT: A method is reported for the preparation of novel electrode by layer-by-layer assembly of haemoglobin (Hb), gold (Au) nanoparticles, chitosan (CS) and graphene (GR) onto glassy carbon electrode (GCE). The Au/GR–CS substrate shows an obvious promotion for the direct electron transfer between Hb and GCE. The surface concentration (Г*) of Hb on the as-modified electrode can be as high as 4.33 × 10−9 mol/cm2, which is 228 times higher than the theoretical value for Hb monolayer on bare GCE. The Au/GR–CS/GCE shows good electrocatalytic performance for the reduction of hydrogen peroxide within a linear range from 2 to 935 μM, a low detection limit of 0.35 μM (S/N = 3) and high sensitivity of 347.1 mA cm−2 M−1. The Au/GR–CS nanocomposite demonstrates as a versatile matrix for immobilizing redox protein to realize direct electrochemistry and hence prepare efficient and robust biosensor.
Sensors and Actuators B Chemical 07/2014; 197:164–171. DOI:10.1016/j.snb.2014.02.077 · 4.10 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: New ternary composites of MnO2 nanorods, polyaniline (PANI) and graphene oxide (GO) have been prepared by a two-step process. The 100 nm-long MnO2 nanorods with a diameter ~20 nm are conformably coated with PANI layers and fastened between GO layers. The MnO2 nanorods incorporated ternary composites electrode exhibits significantly increased specific capacitance than PANI/GO binary composite in supercapacitors. The ternary composite with 70% MnO2 exhibits a highest specific capacitance reaching 512 F/g and outstanding cycling performance, with ~97% capacitance retained over 5000 cycles. The ternary composite approach offers an effective solution to enhance the device performance of metal-oxide based supercapacitors for long cycling applications.
[Show abstract][Hide abstract] ABSTRACT: Novel amphiphilic perylene-polyglycidol was successfully prepared for graphene dispersion. The intercalating of polyglycidol into graphene multilayers was achieved via pi-pi interactions between perylene core and multilayer graphene structure. The hybrid composite exhibits stable dispersion properties in both water and DMF even for over 2 months.
[Show abstract][Hide abstract] ABSTRACT: The rational preparation of hierarchical MnO2/polypyrrole (PPy)/reduced graphene oxide (rGO) nanosheets in a sandwich structure is presented. By co-assembly of MnO2/GO and PPy/GO into layer-by-layer architecture and reduction of GO, ternary (MnO2, PPy)/rGO composites were first fabricated. The materials were fully characterized in terms of structure, morphology and electrochemical properties. The unique architecture offers the composites good capacitance by taking advantage of the strong synergistic effect of each component. A maximum specific capacitance as high as 404 F g(-1) was obtained for this composite electrode. And over 91% of the initial capacitance was retained after 5000 continuous cycles. The good electrochemical performance and long-term cycling stability make this approach attractive in developing multifunctional hierarchical composites for high-performance supercapacitors.
[Show abstract][Hide abstract] ABSTRACT: Hierarchical plush polypyrrole (PPy) layers intercalated graphene sheets have been prepared by in-situ intercalative chemical polymerization. The as-prepared graphene/PPy nanocomposites have been successfully characterized in terms of composition, morphology, and electrochemical properties. It was found that the chemically modified graphene nanosheets and in-situ polymerized PPy layers formed uniform nanocomposites with homogeneous PPy layers intercalated between the graphene substrates. Such uniform nanostructure together with the observed high conductivities (the highest 1980 S m(-1)) afforded the graphene/PPy composites with high specific capacitance and good cycling stability during the charge-discharge process when used as supercapacitor electrodes. The graphene/PPy (with optimized composition 10:1) based supercapacitors display intriguing performance with a maximum specific capacitance of 650 F g(-1) at 0.45 A g(-1) current density, a highest energy density of 54.0 W h kg(-1) at 1 mA current, and a highest power density of 778.1 W kg(-1) at 5 mA current. Furthermore, the graphene/PPy supercapacitor exhibits an excellent cycling stability with 95% specific capacitance retained after 5000 cycles. The impressive results presented here may open the window for grapheme/PPy composites for their promising applications in high energy density storage system.
[Show abstract][Hide abstract] ABSTRACT: Novel monosubstituted dually cationic cyclodextrins (CDs) have been synthesized by anchoring different alkyl chain spaced imidazolium and ammonium sidearm onto the CD primary ring. These cationic CDs exhibit satisfactory enantioselectivities for amino acids and acidic racemates in aqueous capillary electrophoresis.