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We report the thermodynamics of protein adsorption on negatively charged colloidal gold nanoparticles (GNPs) of 16 nm to 69 nm at pH 7.0. Three biologically important proteins of varying size, namely tetrameric alcohol dehydrogenase (ADH) from

Polyaniline (PANI) nanofibers have been developed by an in situ polymerization technique using three different aromatic carboxylic acids as dopant. All dopants have the same aromatic core containing different numbers of carboxylic acid groups. Four (B4CA), three (B3CA), and two (B2CA) carboxylic acid functionalized organic acids have been selected as a dopant for polymerization of aniline in the presence of ammonium persulfate and the corresponding polyaniline composites are named as B4CAP, B3CAP, and B2CAP respectively. With increasing number of −COOH groups in the dopant, the aspect ratio of the fiber increases. Interestingly, all composites revealing nanotubes have shown very good adsorbing behavior toward water-soluble anionic dyes and dye uptake capacity varies with the aspect ratio of the nanofibers. The maximum dye adsorption efficiency achieved for the B4CAP matrix is ∼300 mg/g toward indigo carmine dye in aqueous solution. The dye uptake ability also depends on the size as well as the charge of t...

A polyaniline (PANi)-carbon quantum dots (CQDs) nanocomposite material with CQDs made from a PEG (polyethylene glycol and NaOH) source was synthesized. This unique synthesis technique was developed to overcome the setbacks of the PEG method by using UG (urea and glycine). PANi was synthesized by chemical oxidation in the presence of CQDs, which were prepared according to the two above-mentioned methods. The sample was further characterized by morphological, optical, and electrochemical experiments. FE-SEM showed ridge-like morphology and UV-Vis studies revealed the presence of PANi and CQDs. HRTEM images gave details on the uniformly distributed polyaniline, which showed lengthy rod-like rough surfaces with interconnected tiny CQDs. The electrochemical results from CV and GCD studies indicated an enhancement of the specific capacitance for sample PCQ-2 (CQDs synthesized via the UG method as a source) compared to only PANi and PCQ-1 (CQDs prepared by the PEG method). The cyclic stability established was 84.5% retention from initial capacitance values over 3000 cycles. A two-electrode prototype device was also developed with the PCQ-2 sample and it achieved a reasonable capacitance of 161.3 mF/cm2 and demonstrated good retention stability over 5000 cycles. These results may be due to a variety of factors related to compositing CQDs (with urea and glycine as a source) with PANi.

Herein, we have reported fully organic acid doped polyaniline nanotube as a metal free electrode material for supercapacitor device fabrication. The energy storage behavior of this polymer greatly depends with morphology of nanostructure that has been optimized by using different number of carboxylic groups functionalized organic acid like benzene dicarboxylic acids (OA2), benzene tricarboxylic acids (OA3) and benzene tetracarboxylic acids (OA4). Prepared nanostructures were characterized by UV–Vis, XRD, FTIR, FESEM and HRTEM. Importantly, the charge storage properties of nanostructure were studied by Cyclic voltammetry (CV), galvanic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS). It has been noticed that benzene tetracarboxylic acids (OA4) doped polyaniline (OA4PAN) is the optimum nanostructure having specific capacitance ~ 400 F/g at 0.5 A/g in the three-electrode system. A symmetrical solid-state device with excellent mechanical flexibility has been fabricated with optimized nanostructure revealed the specific capacitance of 107 F/g at a 0.2 A/g in wide potential window with high cyclic stability up to 5000 cycle at 2 A/g (~91% retention of specific capacitance). This nanostructure could be eligible to use for various energy storage system in near future.

Herein, we have developed a simple and facile technique at 210 °C to obtain nano-structured organic compounds, instead of making carbon dots at a relatively higher temperature. Taking the advantage of stable dispersion of organic nanostructures in an aqueous medium, composite of polyaniline has been developed and subsequently utilized as an active electrode material for supercapacitor application. This composite material confirms noteworthy enhancement in specific capacitance (779 F/g) and also divulges the attractive capacitance retention using three-electrode systems. The suitability of the materials for the solid-state device was tested with a prototype two-electrode device. The symmetric device exhibits 130 F/g gravimetric capacitance and 650 mF/cm2 areal capacitance. The improved performance in the specific capacitance is observed due to the generation of more active charge storage sites in the interfacial interaction of organic nanostructures and polyaniline in the composite. The cyclic stability of the symmetric device reveals excellent retention of 96% in specific capacitance over 5000 cycles.

The effects of pH and ligand binding on the stability of abrin II, a heterodimeric ribosome-inactivating protein, and its subunits have been studied using high-sensitivity differential scanning calorimetry. At pH7.2, the calorimetric scan consists of two transitions, which correspond to the B-subunit [transition temperature (Tm) 319.2K] and the A-subunit (Tm 324.6K) of abrin II, as also confirmed by studies on the isolated A-subunit. The calorimetric enthalpy of the isolated A-subunit of abrin II is similar to that of the higher-temperature transition. However, its Tm is 2.4K lower than that of the higher-temperature peak of intact abrin II. This indicates that there is some interaction between the two subunits. Abrin II displays increased stability as the pH is decreased to 4.5. Lactose increases the Tm values as well as the enthalpies of both transitions. This effect is more pronounced at pH7.2 than at pH4.5. This suggests that ligand binding stabilizes the native conformation of abrin II. Analysis of the B-subunit transition temperature as a function of lactose concentration suggests that two lactose molecules bind to one molecule of abrin II at pH7.2. The presence of two binding sites for lactose on the abrin II molecule is also indicated by isothermal titration calorimetry. Plotting DeltaHm (the molar transition enthalpy at Tm) against Tm yielded values for DeltaCp (change in excess heat capacity) of 27+/-2 kJ.mol-1.K-1 for the B-subunit and 20+/-1 kJ.mol-1.K-1 for the A-subunit. These values have been used to calculate the thermal stability of abrin II and to surmise the mechanism of its transmembrane translocation.