Vittaya Amornkitbamrung

A dye sensitized solar cell using natural counter electrode and natural dye derived from mangosteen peel waste

Mangosteen peel is an inedible portion of a fruit. We are interested in using these residues as components of a dye sensitized solar cell (DSSC). Carbonized mangosteen peel was used with mangosteen peel dye as a natural counter electrode and a natural photosensitizer, respectively. A distinctive mesoporous honeycomb-like carbon structure with a rough nanoscale surface was found in carbonized mangosteen peels. The efficiency of a dye sensitized solar cell using carbonized mangosteen peel was compared to that of DSSCs with Pt and PEDOT-PSS counter electrodes. The highest solar conversion efficiency (2.63%) was obtained when using carbonized mangosteen peel and an organic disulfide/thiolate (T2/T−) electrolyte.

Magnetic and Cytotoxicity Properties of La1−xSrxMnO3(0 ≤ x ≤ 0.5) Nanoparticles Prepared by a Simple Thermal Hydro-Decomposition

This study reports the magnetic and cytotoxicity properties of magnetic nanoparticles of La1−xSrxMnO3(LSMO) withx = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 by a simple thermal decomposition method by using acetate salts of La, Sr, and Mn as starting materials in aqueous solution. To obtain the LSMO nanoparticles, thermal decomposition of the precursor was carried out at the temperatures of 600, 700, 800, and 900 °C for 6 h. The synthesized LSMO nanoparticles were characterized by XRD, FT-IR, TEM, and SEM. Structural characterization shows that the prepared particles consist of two phases of LaMnO3(LMO) and LSMO with crystallite sizes ranging from 20 nm to 87 nm. All the prepared samples have a perovskite structure with transformation from cubic to rhombohedral at thermal decomposition temperature higher than 900 °C in LSMO samples ofx ≤ 0.3. Basic magnetic characteristics such as saturated magnetization (MS) and coercive field (HC) were evaluated by vibrating sample magnetometry at room temperature (20 °C). The samples show paramagnetic behavior for all the samples withx = 0 or LMO, and a superparamagnetic behavior for the other samples havingMSvalues of ~20–47 emu/g and theHCvalues of ~10–40 Oe, depending on the crystallite size and thermal decomposition temperature. Cytotoxicity of the synthesized LSMO nanoparticles was also evaluated with NIH 3T3 cells and the result shows that the synthesized nanoparticles were not toxic to the cells as determined from cell viability in response to the liquid extract of LSMO nanoparticles.

High performance dye-sensitized solar cell based on hydrothermally deposited multiwall carbon nanotube counter electrode

Conductive glass was coated with multiwall carbon nanotubes (MWCNTs) by a hydrothermal method. MWCNTs films were subsequently used as dye-sensitized solar cell (DSSC) counter electrodes. The performance of hydrothermal MWCNT DSSC was ∼2.37%. After film annealing in an Ar atmosphere, annealed-hydrothermal MWCNT (AHT-CNT) DSSC efficiency was significantly increased to ∼7.66%, in comparison to ∼8.01% for sputtered-Pt DSSC. Improvement of AHT-CNT DSSC performance is attributed to a decrease in charge-transfer resistance from 1500 Ω to 30 Ω as observed by electrochemical impedance spectroscopy.

A density functional theory study on peptide bond cleavage at aspartic residues: direct vs cyclic intermediate hydrolysis

In this work, peptide bond cleavages at carboxy- and amino-sides of the aspartic residue in a peptide model via direct (concerted and step-wise) and cyclic intermediate hydrolysis reaction pathways were explored computationally. The energetics, thermodynamic properties, rate constants, and equilibrium constants of all hydrolysis reactions, as well as their energy profiles were computed at the B3LYP/6-311++G(d,p) level of theory. The result indicated that peptide bond cleavage of the Asp residue occurred most preferentially via the cyclic intermediate hydrolysis pathway. In all reaction pathways, cleavage of the peptide bond at the amino-side occurred less preferentially than at the carboxy-side. The overall reaction rate constants of peptide bond cleavage of the Asp residue at the carboxy-side for the assisted system were, in increasing order: concerted < step-wise < cyclic intermediate.

Surface modification of electrospun PCL scaffolds by plasma treatment and addition of adhesive protein to promote fibroblast cell adhesion

Abstract Nanofibres fabricated from synthetic polymers via electrospinnning may be uniform and possess consistent quality; however, due to the nature of polymers, these nanofibres may not serve as suitable substrates for cell adhesion. Thus, the present work is aimed to enhance cell adherence onto the as spun poly(ϵ-caprolactone) (PCL) scaffolds via simple protein absorption, air plasma treatment and protein immobilisation methods. The as spun PCL fibres had average fibre diameter of 475·99 ± 194·52 nm with average porosity of 72·29 ± 1·90%. The laminin absorbed scaffold exhibited 20% increase in cell adhesion compared to the original scaffold. With the plasma treatment, the scaffolds increased their fibre sizes, but no significant change occurred in their porosities. The as spun PCL scaffold treated with air plasma was less hydrophobic and exhibited 66% increase in cell adherence compared to the original scaffold. When laminin protein was also included, a greater increase in cell adhesion was observed (84%). Comparing all methods, a laminin immobilised scaffold, with argon/oxygen plasma treatment followed by protein grafting with acrylic acid, showed the highest result of cell adhesion (96%). The results of the present work demonstrate the comparison of various means of using plasma treatment and laminin protein to enhance cell adherence onto the as spun PCL scaffolds, making it more suitable for tissue engineering and wound dressing applications.

Electrochemically Deposited Polypyrrole for Dye-Sensitized Solar Cell Counter Electrodes

Polypyrrole films were coated on conductive glass by electrochemical deposition (alternative current or direct current process). They were then used as the dye-sensitized solar cell counter electrodes. Scanning electron microscopy revealed that polypyrrole forms a nanoparticle-like structure on the conductive glass. The amount of deposited polypyrrole (or film thickness) increased with the deposition duration, and the performance of polypyrrole based-dye-sensitized solar cells is dependant upon polymer thickness. The highest efficiency of alternative current and direct current polypyrrole based-dye-sensitized solar cells (DSSCs) is 4.72% and 4.02%, respectively. Electrochemical impedance spectroscopy suggests that the superior performance of alternative current polypyrrole solar cells is due to their lower charge-transfer resistance between counter electrode and electrolyte. The large charge-transfer resistance of direct current solar cells is attributed to the formation of unbounded polypyrrole chains minimizing the reduction rate.

DFT and TDDFT study on the electronic structure and photoelectrochemical properties of dyes derived from cochineal and lac insects as photosensitizer for dye-sensitized solar cells.

Essential parameters related to the photoelectrochemical properties, such as ground state geometries, electronic structures, oxidation potential and electron driving force, of cochineal insect dyes were investigated by DFT and TDDFT at the B3LYP/6-31+G(d,p) level of the theory. The results show that the major charge flow dynamic for all dyes is the HOMO→LUMO transition. The bi-coordinated binding mode, in which the dye uses one carboxyl- and hydroxyl oxygen bound to Ti(IV), is found for all dye-TiO2 systems. Additionally, the doubly bi-coordinated binding mode in which the dye used both carboxyl groups bound to two Ti(IV) is also possible due to high energy distribution occupied at anchoring groups. This study highlights that most of these insect dyes can be good photosensitizers in dye-sensitized solar cells based on their strong binding to the TiO2 surface, good computed excited state oxidation potential and thermodynamically favored electron driving force.

Synthesis and thermoelectric properties of Ca3Co4O9 prepared by a simple thermal hydro-decomposition method

Thermoelectric Ca3Co4O9 powders were synthesized by a simple thermal hydro-decomposition method, which is novel, simple and cost effective for preparing such materials. The stoichiometric ratio of the acetate salts was mixed in de-ionized water and heated at 1073 K to obtain a single phase of Ca3Co4O9, which was confirmed by TG-DTA, XRD and chemical analysis. The electron micrograph showed plate-like particles with a diameter of ∼1 µm. The hot-pressed powders show the electrical resistivity of 11.6 mΩcm, the Seebeck coefficient of 200 µV/K, and the thermal conductivity of 1.2 Wm−1K−1 at 880 K, which corresponds to a dimensionless figure-of-merit ZT of 0.23.

Spatially resolved atomic excitation temperatures in CH4/H2 and C3H8/H2 RF discharges by optical emission spectroscopy

Spatially resolved optical emission spectroscopy was used to determine the atomic excitation temperature of the capacitively coupled radio-frequency (RF) plasma system. Low pressure plasmas of methane or propane in hydrogen were excited at 13.56 MHz in a parallel plate system. Ar was added as an actinometer. Optical emission lines in the 300–850 nm spectral range were investigated at typical conditions of 100 W RF power, ~30 mTorr pressure, 20 mm electrode spacing and 50 sccm total flow rate. Two-dimensional intensity profiles of the important species were collected along the vertical and radial axes. The raw radial intensity was transformed into the actual local radiation intensity by Abel inversion. The atomic hydrogen and argon excitation temperature distributions between the power and grounded electrodes were derived from these data and distinct differences were found in methane- and propane-containing plasmas.

High efficiency organic-electrolyte DSSC based on hydrothermally deposited titanium carbide-carbon counter electrodes

AbstractPt-free TiC based electrodes were hydrothermally deposited onto FTO/glass substrates and used as dye-sensitized solar cell (DSSC) counter electrodes. A promising efficiency of 3.07% was obtained from the annealed hydrothermal TiC DSSCs based on a disulfide/thiolate electrolyte. A pronounced improvement in performance of 3.59% was achieved by compositing TiC with carbon, compared to that of a Pt DSSC, 3.84%. TEM analysis detected that the TiC particle surfaces were coated by thin carbon layer (7 nm). The SAED pattern and Raman spectrum of TiC-carbon films suggested that the carbon layer was composed of amorphous and graphite carbon. The formation of graphite on the TiC nanoparticles plays a crucial role in enhancing the film’s reduction current to 10.12 mA/cm2 and in reducing the film impedance to 237.63 Ω, resulting in a high efficiency of the TiC-carbon DSSC.