Second and third-order nonlinear optical behavior of natural pigment: chlorophyll and crocin

To provide an insight into the microscopic second and third-order nonlinear optical (NLO) behavior of chlorophyll a and crocin, we have computed the electric dipole moments (μ), dispersion-free first hyperpolarizabilities (β), frequency-dependent first and second (γ) hyperpolarizabilities at 1064 nm wavelength area using time-dependent Hartree-Fock (TDHF) method. According to ab-initio calculation results, the examined compounds exhibit first and second hyperpolarizabilities with non-zero values, implying second and third-order NLO phenomena

Computational studies on linear, second and third-order nonlinear optical properties of novel styrylquinolinium dyes

The electric dipole moments (μ), static dipole polarizabilities (α) and first hyperpolarizabilities (β) of styrylquinolinium dyes, D8 and D21, have been computed by density functional theory (DFT). The one-photon absorption (OPA) characterizations have been investigated using UV–vis spectroscopy and further interpreted using computational chemistry. The time-dependent Hartree–Fock (TDHF) method has been used to describe the dynamic dipole polarizabilities, dynamic second-order and also static and dynamic third-order nonlinear optical (NLO) properties. D8–D21 have rather high β and second hyperpolarizabilities (γ). The highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO) and the HOMO–LUMO band gaps for D8–D21 have been evaluated by DFT

Characterisation of plasticised PVDF–HFP polymer electrolytes

This study focuses on the preparation and characterisation of sodium ion conducting polymer electrolytes. Poly(vinylidenefluoride-co-hexafluoropropylene) has been used as the host matrix and hydrated sodium sulphide (Na2S.9H2O) salt as the source of charge carriers in the polymer electrolyte system. To the highest conducting polymer–salt electrolyte, different concentrations of equal weight of propylene carbonate and diethyl carbonate mixture have been added, and the electrolytes have been characterised by X-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy and electrochemical impedance spectroscopy. The room temperature ionic conductivity of 1?3461024 S cm21 for the unplasticised electrolyte with a composition of 65 wt-% poly(vinylidenefluoride-co-hexafluoropropylene)–35 wt-%Na2S increased to 3?4961024 S cm21 when 30 wt-% propylene carbonate/diethyl carbonate (w/w51) plasticisers were added

Fabrication, Characterization, and Optimization of CdS and CdSe Quantum Dot-Sensitized Solar Cells with Quantum Dots Prepared by Successive Ionic Layer Adsorption and Reaction

CdS and CdSe quantum dot-sensitized solar cells (QDSSCs) were used for the study of determining the optimum preparation parameters that could yield the best solar cell performance. The quantum dots (QDs) were coated on the surface of mesoporous TiO2 layer deposited on FTO substrate using the successive ionic layer adsorption and reaction (SILAR) method. In this method the QDs are allowed to grow on TiO2 by dipping the TiO2 electrode successively in two different solutions for predetermined times. This method allows the fabrication of QDs in a facile way. Three preparation parameters that control the QD fabrication were investigated: concentration of precursor solutions, number of dipping cycles (SILAR cycles), and dipping time in each solution. CdS based QDSSC showed optimum performance when the QDs were prepared from precursor solutions having the concentration of 0.10 M using 4 dipping cycles with the dipping time of 5 minutes in each solution. For CdSe QDSSC, the optimum performance was achieved with QDs prepared from 0.03 M precursor solutions using 7 dipping cycles with 30 s dipping time in each solution. The QDs deposited on TiO2 surface were characterized using UV-vis absorption spectroscopy, FESEM, and TEM imaging

A Suitable Polysulfide Electrolyte for CdSe Quantum Dot-Sensitized Solar Cells

A polysulfide liquid electrolyte is developed for the application in CdSe quantum dot-sensitized solar cells (QDSSCs). A solvent consisting of ethanol and water in the ratio of 8 : 2 by volume has been found as the optimum solvent for preparing the liquid electrolytes. This solvent ratio appears to give higher cell efficiency compared to pure ethanol or water as a solvent. Na2S and S give rise to a good redox couple in the electrolyte for QDSSC operation, and the optimum concentrations required are 0.5 M and 0.1 M, respectively. Addition of guanidine thiocyanate (GuSCN) to the electrolyte further enhances the performance. The QDSSC with CdSe sensitized electrode prepared using 7 cycles of successive ionic layer adsorption and reaction (SILAR) produces an efficiency of 1.41% with a fill factor of 44% on using a polysulfide electrolyte of 0.5 M Na2S, 0.1 M S, and 0.05 M GuSCN in ethanol/water (8 : 2 by volume) under the illumination of 100 mW/cm2 white light. Inclusion of small amount of TiO2 nanoparticles into the electrolyte helps to stabilize the polysulfide electrolyte and thereby improve the stability of the CdSe QDSSC. The CdSe QDs are also found to be stable in the optimized polysulfide liquid electrolyte

Multi-wavelength fiber laser with erbium doped zirconia fiber and semiconductor optical amplifier

Multi-wavelength hybrid fiber lasers are demonstrated in both ring and linear cavities using a fabricated Erbium-doped Zirconia fiber (EDZF) and semiconductor optical amplifier (SOA) as gain media. In both configurations, the a fiber loop mirror, which is constructed using a 3 m long polarization maintaining fiber (PMF) and a polarization insensitive 3dB coupler is used as a comb filter for the fiber laser. In the ring cavity, 10 simultaneous lines with peak power above -26 dBm is obtained at 1550 nm region. This is an improvement compared to the linear cavity configuration which has only 5 simultaneous lines observed from wavelength 1556.1 nm to 1563.0 nm with the peak power above -40 dBm. Both hybrid lasers has a constant line spacing of 1.7 nm, which is suitable for wavelength division multiplexing and sensing applications and shows a stable operation at room temperature

Contractor's performance appraisal system in the Malaysian construction industry: Current practice, perception and understanding

Performance appraisal system is a common practice in any organisation to appraise performance of workers. In the Malaysian construction industry, performance appraisal system is applied to appraise contractor's performance in many angles including: quality performance; time performance; cost performance; environmental performance; health and safety performance; productivity performance; and human resources performance. This is where the Construction Industry Development Board (CIDB) established three guidelines in strengthening the Construction Industry Transformation Programme (CITP) by appraising the contractor's performance through identification of their weaknesses as well as drafting and offering suitable trainings in enhancing their performance. This paper is therefore undertaken with the objectives of: (1) determining the current practice of contractor's performance appraisal system in the Malaysian construction industry; and (2) examining the construction players' perception and understanding on the existing contractor's performance appraisal system in the Malaysian construction industry. A set of questionnaires is designed and distributed to 157 contractors from G1 to G7 class. The paper finds that: (1) contractor's performance appraisal system is benefiting the contractors yet should be improved for its efficiency; and (2) construction players have sufficient understanding on contractor's performance appraisal system. It is expected that the improvement of contractor's performance appraisal system via the findings of this paper would assist in achieving the three focuses of Transformasi Nasional 2050 (TN50), namely science and technology, urban prosperity as well as environment

Phthaloylchitosan-Based Gel Polymer Electrolytes for Efficient Dye-Sensitized Solar Cells

Phthaloylchitosan-based gel polymer electrolytes were prepared with tetrapropylammonium iodide, Pr 4 NI, as the salt and optimized for conductivity. The electrolyte with the composition of 15.7 wt.% phthaloylchitosan, 31.7 wt.% ethylene carbonate (EC), 3.17wt.% propylene carbonate (PC), 19.0 wt.% of Pr 4 NI, and 1.9wt.% iodine exhibits the highest room temperature ionic conductivity of 5.27 x 10 -3 S cm -1. The dye-sensitized solar cell (DSSC) fabricated with this electrolyte exhibits an efficiency of 3.5% with.. SC of 7.38mAcm -2,.. OC of 0.72V, and fill factor of 0.66. When various amounts of lithium iodide (LiI) were added to the optimized gel electrolyte, the overall conductivity is observed to decrease. However, the efficiency of the DSSC increases to a maximum value of 3.71% when salt ratio of Pr 4 NI : LiI is 2 : 1. This cell has.. SC,.. OC and fill factor of 7.25mAcm -2, 0.77V and 0.67, respectively

Design of a modular testing platform for the handling and study of endovascular devices

A design for a modular testing platform to objectively evaluate the behavior and characteristics of specialized endovascular instruments (guidewires/catheters) was presented and discussed. The platform comprises of an instrument driving mechanism and an interchangeable channel module depending on the parameter that is being measured. This platform could be used to study and benchmark commercial endovascular instruments. Such a guide would be useful to assist clinicians in the selection of the best tools for a given procedure and derive the behavioral model for each instrument