RESUMO
In this work, multiwalled carbon nanotubes (MWCNTs) are functionalized using 4-nitrobenzenediazonium (NBD) salt, which is identified as an effective electrocatalyst for the detection of ß-nicotinamide adenine dinucleotide (NADH). The NBD functionalized MWCNT (NBD-MWCNT(w) (w-washed)) was characterized using various physicochemical characterization methods. Cyclic voltammetric measurements showed that NBD-MWCNT(w) modified glassy carbon electrode (NBD-MWCNT(w)/GCE) was able to produce the anodic wave for oxidizing NADH at the applied overpotential of 0.12 V, which is 0.67 V cathodic when compared to that of bare GCE. Besides, the sensitivity of the electrode also doubled. The sensitivity and limit of detection (LoD) were 8.5 × 10-4 A M-1 and 3.75 µM, respectively. The linear range of the sensor was 5 to 60 µM. The selectivity studies further proved that the matrix is specific towards detecting NADH in the presence of other possible interfering molecules. The diffusion co-efficient and apparent rate constant of NADH obtained were 3.8 × 10-6 cm2 s-1 and 1.12 × 107 mol-1 cm3 s-1 respectively. Additionally, the electrode is employed to detect the analyte in real samples.
RESUMO
Excited-state properties of two novel metal-free custom-made dyes D2d [(Z)-2-cyano-3-(4-((E)-2-(6-(4-methoxyphenyl)-9-octyl-9H-carbazol-3-yl)vinyl)phenyl)acrylic acid] and T-SB-C [(E)-2-cyano-3-(4-((E)-4-(diphenylamino)styryl)phenyl)acrylic acid] and two commercially available Ruthenium-based N719 and Z907 dyes were investigated with application of time-resolved absorption and emission. Singlet excited state lifetimes of D2d and T-SB-C were determined in acetonitrile and are 1.4 and 2.45 ns, respectively. The 3MLCT state lifetimes of N719 and Z907 dyes determined in methanol are 9.25 and 8.85 ns, respectively. Subsequently, photoexcited processes like electron injection and charge recombination were studied for those dyes adsorbed on the FTO/TiCl4/TiO2 photoanodes and fabricated via a conventional staining technique and innovative potential-assisted fast dye staining method. The dynamics of the spectro-temporal data was determined with application of single-wavelength and global fitting. All dye-TiO2 systems showed fast picosecond injection of excited electrons to the conduction band of the TiO2 layer and in complex multiphasic charge recombination processes. The dynamics of those processes is not altered by the dye adsorption method.
