Metal nanoparticles that comprise a few hundred to several thousand atoms have many applications in areas such as photonics, sensing, medicine and catalysis. Colloidal methods have proven particularly suitable for producing small nanoparticles with controlled morphologies and excellent catalytic properties. Ligands are necessary to stabilize nanoparticles during synthesis, but once the particles have been deposited on a substrate the presence of the ligands is detrimental for catalytic activity. Previous methods for ligand removal have typically involved thermal and oxidative treatments, which can affect the size or morphology of the particles, in turn altering their catalytic activity. Here, we report a procedure to effectively remove the ligands without affecting particle morphology, which enhances the surface exposure of the nanoparticles and their catalytic activity over a range of reactions. This may lead to developments of nanoparticles prepared by colloidal methods for applications in fields such as environmental protection and energy production.

Facile removal of stabilizer-ligands from supported gold nanoparticles

A conceptual review on polymer electrolytes and ion transport models

The (chitosan–PVA)–NH 4 I electrolytes have been prepared by the solution casting method. The prepared electrolytes are analyzed using Fourier transform infrared (FTIR) spectroscopy in order to determine the interaction between salt and the polymer blend hosts which can be deduced from the band shifting. From infrared spectra, shifts are observed at the amine, carboxamide, carbonyl and hydroxyl bands of chitosan and PVA. These shifts indicate that complexation has occurred. The crystallinity/amorphousness of the blended electrolytes has been examined by X-ray diffraction (XRD). XRD pattern shows that the crystallinity of chitosan–NH 4 I electrolyte increases with PVA concentration. Impedance of the electrolytes has been measured using electrochemical impedance spectroscopy (EIS) over the frequency range from 50 Hz to 1 MHz. The highest conducting sample 55 wt.% (chitosan–PVA)–45 wt.% NH 4 I has conductivity of 1.77 × 10 − 6  S cm − 1 . The chitosan:PVA ratio is 1:1. This is higher than the conductivity for the unblended electrolyte 55 wt.% chitosan–45 wt.% NH 4 I which is 3.73 × 10 − 7  S cm − 1 . From ln τ versus 10 3 / T plot, the activation energy for relaxation process is 0.87 eV. This is different from activation energy for dc conductivity which is 0.38 eV. Ion conduction is by hopping.

Characterization of chitosan/PVA blended electrolyte doped with NH4I

Understanding the mechanisms of lithium-ion transport in polymers is crucial for the design of polymer electrolytes. We combine modular synthesis, electrochemical characterization, and molecular simulation to investigate lithium-ion transport in a new family of polyester-based polymers and in poly(ethylene oxide) (PEO). Theoretical predictions of glass-transition temperatures and ionic conductivities in the polymers agree well with experimental measurements. Interestingly, both the experiments and simulations indicate that the ionic conductivity of PEO, relative to the polyesters, is far higher than would be expected from its relative glass-transition temperature. The simulations reveal that diffusion of the lithium cations in the polyesters proceeds via a different mechanism than in PEO, and analysis of the distribution of available cation solvation sites in the various polymers provides a novel and intuitive way to explain the experimentally observed ionic conductivities. This work provides a platform for the evaluation and prediction of ionic conductivities in polymer electrolyte materials.

https://pubs.acs.org/doi/pdf/10.1021/acscentsci.5b00195

Systematic Computational and Experimental Investigation of Lithium-Ion Transport Mechanisms in Polyester-Based Polymer Electrolytes.

article i nfo The development of new biopolymer electrolytes (BEs) based on carboxy methylcellulose (CMC) has been accomplished by incorporating dodecyltrimethyl ammonium bromide (DTAB) to the polymer-salt system via solution-cast technique. The polymer-salt complex formation and the polymer-proton interactions have been analyzed through Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) mea- surement, impedance measurement and Transference number measurement (TNM). The highest conductiv- ity at room temperature is 7.72×10 �4 Scm �1 for sample containing 35 wt. % DTAB. The temperature dependence of the BEs system exhibits Arrhenius behavior. The conductivity of the samples was found to be dependent on the number of mobile ions and the mobility of the ions. It has been shown that the conduct- ing species in this present work are predominantly due to proton (H + ) which was confirmed via FTIR and TNM analysis. The results suggest that BEs system is highly potential to be applied in electrochemical devices, i.e. proton battery and fuel cell.

Characterization on the potential of carboxy methylcellulose for application as proton conducting biopolymer electrolytes

Thermal and dielectric studies of polymer electrolyte based on P(ECH-EO)

Laser Raman and ac impedance spectroscopic studies of PVA: NH4NO3 polymer electrolyte.

An attempt has been made to prepare a new proton conducting polymer electrolyte based on polyvinyl alcohol (PVA) doped with NH4NO3 by solution casting technique. The complex formation between polymer and dissociated salt has been confirmed by X-ray diffraction analysis. The ionic conductivity of the prepared polymer electrolyte has been found by ac impedance spectroscopic analysis. The highest ionic conductivity has been found to be 7.5 × 10−3 Scm−1 at ambient temperature for 20 mol% NH4NO3-doped PVA with low activation energy (~0.19 eV). The temperature-dependent conductivity of the polymer electrolyte follows an Arrhenius relationship, which shows hopping of ions in the polymer matrix.

Structural and ionic conductivity studies on proton conducting polymer electrolyte based on polyvinyl alcohol

Lanthanum fluoride nanoparticles have been synthesized by the simple method of direct precipitation from an aqueous solution. TG/DTA analysis confirms the sample formation at low temperature (300 °C). Structure of LaF3 nanoparticles has been analyzed by XRD and LaF3 is found to be in tysonite structure. From the XRD spectra the average particle size is found to be 15 nm using the Scherrer formula. The impedance, modulus and dielectric spectra analysis of the prepared LaF3 nanoparticles has been studied using AC impedance spectroscopy. The ionic conductivity of LaF3 nanoparticles is significantly increased by an order from 10−6 to 10−5 S cm−1. The modulus and dielectric spectra analysis confirms the non-Debye type behavior in the material.

S. Selvasekarapandian

Papers

Thermal and dielectric studies of polymer electrolyte based on P(ECH-EO)

Laser Raman and ac impedance spectroscopic studies of PVA: NH4NO3 polymer electrolyte.

Structural and ionic conductivity studies on proton conducting polymer electrolyte based on polyvinyl alcohol

Dielectric, modulus and impedance analysis of LaF3 nanoparticles

Effect of calcium doping on LaCoO3 prepared by Pechini method