Composites of few layered graphene (G) and platinum (Pt) nanoparticles (NP) with different loadings of Pt were used as counter electrode (CE) in dye-sensitized solar cell (DSSC). NPs were deposited directly on to G using pulsed laser ablation method (PLD). DSSCs formed using the composite CEs show improved performance compared to conventional Pt thin film electrode (Std Pt) and unsupported Pt NPs. Composite with 27% loading of Pt shows 45% higher efficiency (η = 2.9%), greater short circuit current (J(sc) = 6.67 mA cm(-2)), and open circuit voltage (V(oc) = 0.74 V) without any loss of the fill factor (FF = 58%) as compared to the cells fabricated using Std Pt electrodes. Values of η, J(sc) and V(oc) for DSSC using Std Pt CE were 2%, 5.05 mA cm(-2) and 0.68 V, respectively. Electrochemical impedance spectroscopy using I(-)(3)/I(-) redox couple confirm lower values of charge transfer resistance for the composite electrodes, e.g., 2.36 Ω cm(2) as opposed to 7.73 Ω cm(2) of Std Pt. The better catalytic activity of these composite materials is also reflected in the stronger I(-)(3) reduction peaks in cyclic voltammetry scans.

A platinum free counter electrode for dye sensitized solar cells was developed using graphene platelets (GP) supported nickel nanoparticles (NPs) as the active catalyst. Few layered GP were prepared by chemical oxidation of graphite powders followed by thermal exfoliation and reduction. The nanoparticles of nickel were deposited directly onto the platelets by pulsed laser ablation. The composite electrodes of GP and Ni nanoparticles (GP-Ni) thus obtained showed better performance compared to conventional Pt thin film electrodes (Std Pt) and unsupported Ni NPs. The efficiencies of the cells fabricated using GP-Ni, Std Pt and Ni NP CEs were 2.19%, 2% and 1.62%, respectively. The GP-Ni composite solar cell operated with an open circuit voltage of 0.7 V and a fill factor of 0.6. Electrochemical impedance spectroscopy using the I(3)(-)/I(-) redox couple confirms lower values of charge transfer resistance for the composite electrodes, 4.67 Ω cm(2) as opposed to 7.73 Ω cm(2) of Std Pt. The better catalytic capability of these composite materials is also reflected in the stronger I(3)(-) reduction peaks in cyclic voltammetry scans.

By exploiting the presence of abundant carboxylic groups (-COOH) on graphene oxide (GO) and using EDC-NHS (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride-N-hydroxysuccinimide) chemistry to covalently conjugate protein molecules, we demonstrate a novel electrochemical immunosensor for detection of antibody-antigen (Rabbit IgG-AntiRabbit IgG) interactions. The interactions were verified using Electrochemical Impedance Spectroscopy (EIS). Although GO is known to be a poor conductor, the charge transfer resistance (R P) of a GO modified glassy carbon electrode (GCE) was found to be as low as 1.26 U cm 2. This value is similar to that obtained for reduced graphene oxide (RGO) or graphene and an order of magnitude less than bare GCE. The EIS monitored antibody-antigen interactions showed a linear increase in R P and the overall impedance of the system with increase of antibody concentration. Rabbit IgG antibodies were detected over a wide range of concentrations from 3.3 nM to 683 nM with the limit of detection (LOD) estimated to be 0.67 nM. The sensor showed high selectivity towards Rabbit IgG antibody as compared to non-complementary myoglobin. RGO modified GCE showed no sensing properties due to the removal of carboxylic groups which prevented subsequent chemical functionalization and immobilization of antigen molecules. The sensitivity and selectivity achievable by this simple label free technique hint at the possibility of GO becoming the electrode material of choice for future electrochemical sensing protocols.

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Presence of abundant pores and highly entangled nanotubes make bucky paper (BP) a natural candidate for filtration related applications. Both single-and multiwall carbon nanotube (SWNT and MWNT) BPs were fabricated via self-assembly. Average diameter of the pores on the surface of MWNT BP appeared to be 33 ± 15 nm. However, due to the high tortuousity of BP, the cutoff size, estimated by filtration of colloidal dispersions of Au and CdS nanoparticles of different diameters, turned out to be 4−5 nm. The particle sizes were verified using microscopic and spectroscopic methods. The flux of Au nanoparticle solutions through BP was about 1000 L h −1 m −2 bar −1 . Highly flexible and robust SWNT BPs were prepared very easily, even without proper dispersion. It was found that the crystallinity and purity of the SWNTs had a bigger role than the quality of dispersion in determining the final mechanical strength of BP. The density of SWNT BP was estimated to be 1.3 ± 0.3 g/cm 3 after correcting for the weights of the impurities. This is among the highest ever reported. The average wall to wall separation of adjacent tubes was estimated to be 0.35 ± 0.2 nm, which is very close to the ideal value. The SWNT BP was also found to be impervious to liquids such as water, n-hexane, acetone, and isopropyl alcohol, indirectly verifying its close knit structure and small pore size. This is indicative of its possible use as a molecular sieve membrane.