Maximum Absorption Wavelength Research Articles

Investigation of linear and second-order nonlinear optical properties of donor-acceptor interaction derivatives based on acceptor DCPPr core

Red thermally activated delayed fluorescence (TADF) materials have attracted much attention from researchers due to their potential applications in display and lighting devices. Recently, DCPPr-TPA has displayed unique photophysical properties, such as high optical out-coupling factor and near infrared (NIR) emissions. However, its structure-property relationship has not been fully detected, which will further improve their performance. Herein, based on the reported DCPPr-TPA, four new derivatives are designed by inserting π-bridge ethylene units, introducing donor NO2 units or acceptor NH2 units, and replacing TPA unit with NI unit. Their linear and second-order nonlinear optical properties are investigated in detail using DFT and TD-DFT theories. It is concluded that the insertion of π-bridge ethylene units and the introduction of the donor NH2 units on TPA units are the most effective methods to reduce the energy gap, redshift the maximum absorption wavelength and increase the first hyperpolarizability. The four newly designed derivatives do not further enhance hole transport ability, but derivatives 1–3 do enhance electron transport ability, and derivatives 1–3 are all potential bipolar transport materials. In view of their large first hyperpolarizability, the studied derivatives may become second-order nonlinear optical (NLO) materials with excellent properties.

Effect of Dispersant on Disperse Dyeing in Silicone Waterless Dyeing System

Traditional water-based dyeing of polyester textiles usually generates burdensome processes and a great deal of wastewater, which can no longer meet the green and sustainable developments in the textile dyeing industry. In the silicone waterless dyeing system, polyester textiles can be dyed with disperse dye without water. However, the dyeing performance of polyester textiles is influenced by the dispersant. In this study, the relationship between the properties of dispersants and disperse dyeing performance was studied. When the amount of dispersant NNO (2-Naphthalenesulfonic acid) was 1.2%, the exhaustion of disperse red 177 and the final K/S value of the dyed fabric improved to 94.18% and 14.73, respectively. However, the exhaustion of disperse red 177 was reduced from 90.73% to 82.61%, and the final K/S value of the dyed fabric was decreased from 14.77 to 14.01 when the dosage of MF (Naphthalenesulfonic acid) was 1.2%. Compared with different dyeing systems, the final uptake of disperse red 177 was 93.81% and 94.18% in traditional water-based and silicone waterless dyeing systems and the K/S value of the dyed fabric was almost the same. The washing and rubbing fastness (wet and dry) of the dyed fabric were found to be at a level of 4 or 4-5, and the light fastness of the dyed fabric was 3-4. If only the dispersant was added in the silicone waterless dyeing system, there was no leveling problems on dyed samples. Moreover, the maximum absorption wavelength of disperse red 177 was not changed after adding the dispersant. With an increasing amount of dispersant NNO, the solubility of the dye in the silicone solvent decreased, but it increased with an increasing amount of dispersant MF. In the relationship between dye exhaustion and dye solubility in a silicone waterless dyeing system, the exhaustion of dye was linearly and inversely proportional to the dye solubility. A dispersant with better hydrophilicity can decrease the solubility of the dye in dyeing media, and the dyeing performance of dye is better. Compared with previous studies, the exhaustion of dye was consistent with the ClogP value (hydrophobic constant) of the dyeing accelerant. Therefore, a dispersant with high hydrophilicity can reduce the solubility of dye and improve the exhaustion of disperse dye in a silicone waterless dyeing system. Moreover, the color fastness of the dyed fabric did not change before and after adding the dispersant.

Designing Excess Electron Compounds by Substituting Alkali Metals to a Small and Versatile Tetracyclic Framework: A Theoretical Perspective.

Organic compound-based nonlinear optical (NLO) materials have sparked a lot of attention due to their multitude of applications and shorter optical response times than those of inorganic NLO materials. In the present investigation, we designed exo-exo-tetracyclo[6.2.1.13,6.02,7]dodecane (TCD) derivatives, which were obtained by replacing H atoms of methylene bridge carbon with alkali metals (Li, Na, and K). It was observed that upon the substitution of alkali metals at bridging CH2 carbon, absorption within the visible region occurred. Moving from 1 to 7 derivatives, the maximum absorption wavelength of the complexes exhibited a red shift. The designed molecules showed a high degree of intramolecular charge transfer (ICT) and excess electrons in nature, which were responsible for rapid optical response time and significant large molecular (hyper)polarizability. Calculated trends also inferred that the crucial transition energy decreased in order that also played a key role in the higher nonlinear optical response. Furthermore, to examine the effect of the structure/property relationship on the nonlinear optical properties of these investigated compounds (1-7), we calculated the density of state (DOS), transition density matrix (TDM), and frontier molecular orbitals (FMOs). The largest first static hyperpolarizability (βtot) of TCD derivative 7 was 72059 au, which was 43 times greater than that of the prototype p-nitroaniline (βtot = 1675 au).

Exploring quantum computational, molecular docking, and molecular dynamics simulation with MMGBSA studies of ethyl-2-amino-4-methyl thiophene-3-carboxylate

2-aminothiophenes derivative, Ethyl-2-amino-4-methyl thiophene-3-carboxylate (EAMC) has been synthesized, characterized, and investigated quantum chemically. It was experimentally investigated by different spectroscopic methods like- NMR (1H-NMR and 13C-NMR), FT-IR, and UV-Visible. B3LYP method and 6-311++G(d,p) basis set were employed for optimization of molecular structure and calculation of wave numbers of normal modes of vibrations and various other important parameters. Calculated bond lengths and angles were compared with the experimental bond lengths and Bond Angle Parameters. Optimized bond parameters and experimental bond parameters were found in good agreement. Complete potential energy distribution assignments were done successfully by VEDA. The HOMO/LUMO energy gap emphasizes adequate charge transfer happening within the molecule. A study of donor-acceptor interconnections was done via NBO analysis. MEP surface analysis was done to demonstrate charge distribution and reactive areas qualitatively in the molecule. The degree of relative localization of electrons was analyzed via ELF Diagram. The Fukui function analysis showed possible sites for attacks by different substituents. By using the TD-DFT method and PCM solvent model, the UV–Vis spectrum (gas, methanol, DMSO) and the maximum absorption wavelength was computed and compared with experimental data. 3D and 2D intermolecular interactions in the crystal were analyzed via Hirshfeld surface analysis and fingerprint plots reveal that the EAMC crystal was stabilized by H–-H/H–-H/C–-H bond formation. The molecular docking was done with 7 different protein receptors on the molecule to find the best ligand-protein interactions. Molecular dynamic simulations and MMGBSA calculations were also carried out to find out the best binding of the ligand with the protein. Communicated by Ramaswamy H. Sarma

Heteroatom substitution controlled luminescent property and excited state intramolecular proton transfer (ESIPT) process of novel benzothiazole-based fluorophore: A TD-DFT investigation

By using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, we have systematically explored the spectral characteristics and excited state intramolecular proton transfer (ESIPT) processes of 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methylbenzaldehyde (BTFM-OH) and its derivatives. The sulfur (S) atom in the thiazole ring of BTFM-OH was replaced by O/Se atom (denoted to BOFM-OH/BSeFM-OH) to probe the impact of heteroatom substitution on the luminescent property and ESIPT process. The simulated maximum absorption and fluorescence wavelengths of BTFM-OH are well consistent with the experimental values. From BOFM-OH to BTFM-OH and BSeFM-OH, the red-shifts of absorption and fluorescence (at normal and tautomer forms) wavelengths are found, which is in good accordance with the decreasing order of ground state and excited state HOMO-LUMO gaps of BOFM-OH < BTFM-OH < BSeFM-OH. According to the data obtained from structure, infrared vibrational frequency and electron density, it can be found that the intramolecular hydrogen bonds (IHBs) are enhanced in the S1 state, which is favorable to ESIPT process. From BOFM-OH to BTFM-OH and BSeFM-OH, the atomic electron-withdrawing ability of heteroatom is decreasing from O to S and Se, the IHB strengths become stronger in the order of BOFM-OH < BTFM-OH < BSeFM-OH, which makes the ESIPT process occur much easier along this order.

Development and Validation of New Spectrophotometric Methods for the Quantitative Estimation of Naftopidil in Bulk and Pharmaceutical Formulation

Four simple, sensitive, precise and accurate spectrophotometric methods A, B, C and D have been developed for the quantitative estimation of Naftopidil. UV method (A) has been developed by using alcohol as the solvent. The wavelength of maximum absorbance selected was 269nm. The method was linear between the range of 2-10g/ml with correlation coefficient of 0.9999. %RSD of precision was calculated and found to be 0.965. Colorimetric Methods B, C and D have been developed by oxidation followed by complex formation reaction using 1,10- phenanthroline, 2,2’- bipyridyl and Potassium ferricyanide respectively, using ferric chloride as oxidizing agent. Regression analysis for the methods was carried out and the correlation coefficient was found to be between the range of 0.99969-0.9999 depicting very good linear relationship between the concentration of the drug and corresponding absorbance values. % RSD of precision for the three colorimetric methods was calculated and found between the range of 0.4126-1.1354 showing that the methods are precise. Accuracy studies were carried out at three different levels and the results fall between the range of 99.89 to 99.96.

The characteristics of ultraviolet absorption and electronic excitation of sulfate at high concentrations

The variation of spectra and the characteristics of electronic excitation are critical for establishing a model for quantifying sulfate at high concentrations. The absorption characteristics of sulfate are affected by the optical pathlength and sulfate concentration. The absorption coefficient declines by approximately 86.09–96.20% with an increasing concentration (0–130 g/L) at different optical pathlengths (1–100 mm). Moreover, a high sensitivity and accuracy can be achieved at weak absorption wavelengths or at lower optical pathlengths when high concentrations of sulfate are detected. In addition, the maximum absorption wavelength of sulfate redshifts by approximately 0–10 nm with an increasing concentration and optical pathlength, which is significantly affected by the optical pathlength. The (H2SO4)n‧(H2O)4-n models were established at the PBEPBE/6–311++G(d, p) level of theory. There absorption spectra were calculated by the time-dependent density functional theory (TD-DFT) method. As a result, the maximum absorption wavelength redshifted from 180.16 nm to 192.71 nm with an increasing sulfate concentration, and the corresponding absorption coefficient demonstrated a declining trend. Furthermore, the electron-hole and natural bond orbital (NBO) analysis indicate that the type of electronic excitation changes from a n(O) → σ*(S-O) localized excitation to n → σ* charge-transfer excitation as the sulfate concentration increases. This study provides a theoretical foundation for understanding the spectral behavior of sulfates and constructing the quantification models or methods that can also be applied to analyze the spectroscopy of other chemicals.

Dinuclear Phenoxo-Bridged Nickel(II) and Copper(II) Complexes of Phenolate-Based Tripodal Ligand: Theoretical and Experimental Insights

Three dinuclear complexes of composition [NiII 2(L)2][ClO4]2 and [CuII 2(L)2(OClO3)2] . 3H2O have been synthesized using a new tripodal ligand [(2-pyridyl)methyl](2-benzyl)-aminomethyl}-phenol (HL)], in its deprotonated form, providing a N2O donor set. Crystallographic analyses reveal that [CuII 2(L)2(OClO3)2] . 3H2O has a diphenoxo-bridged structure. In [CuII 2(L)2(OClO3)2] . 3H2O, each metal center is MIIN2O3-coordinated with a square-pyramidal environment for each copper(II) center. In this work, the molecular structure, harmonic vibrational frequencies and UV-Vis of [NiII 2(L)2]2+ and [CuII 2(L)2]2+ has been explored. With the help of density functional theory (DFT)/B3LYP techniques and LANL2DZ as a basis set, the ground-state molecule shape and vibrational frequencies were computed. The basic vibrations were allocated using the VEDA program to compute the potential energy distribution (PED) of the vibrational modes. The band gap energies of the title complexes ([NiII 2(L)2]2+ and [CuII 2(L)2]2+) are 3.21 eV and 1.59 eV, respectively, according to HOMO-LUMO energies. The maximal absorption wavelength and band gap energy of the title complexes were calculated theoretically using the UV absorption spectra. MEP analysis identifies electrophilic and nucleophilic sites. Hirshfeld surface analysis was used to characterize the 3D intermolecular interactions in ([NiII 2(L)2]2+ and [CuII 2(L)2]2+) of the crystal surface, whereas fingerprint plots were used to explain the 2D interactions. The biological activity of the complexes was investigated using molecular docking.

Alternative Strategy for Spectral Tuning of Flavin-Binding Fluorescent Proteins.

iLOV is an engineered flavin-binding fluorescent protein (FbFP) with applications for in vivo cellular imaging. To expand the range of applications of FbFPs for multicolor imaging and FRET-based biosensing, it is desirable to understand how to modify their absorption and emission wavelengths (i.e., through spectral tuning). There is particular interest in developing FbFPs that absorb and emit light at longer wavelengths, which has proven challenging thus far. Existing spectral tuning strategies that do not involve chemical modification of the flavin cofactor have focused on placing positively charged amino acids near flavin's C4a and N5 atoms. Guided by previously reported electrostatic spectral tunning maps (ESTMs) of the flavin cofactor and by quantum mechanical/molecular mechanical (QM/MM) calculations reported in this work, we suggest an alternative strategy: placing a negatively charged amino acid near flavin's N1 atom. We predict that a single-point mutant, iLOV-Q430E, has a slightly red-shifted absorption and fluorescence maximum wavelength relative to iLOV. To validate our theoretical prediction, we experimentally expressed and purified iLOV-Q430E and measured its spectral properties. We found that the Q430E mutation results in a slight change in absorption and a 4-8 nm red shift in the fluorescence relative to iLOV, in good agreement with the computational predictions. Molecular dynamics simulations showed that the carboxylate side chain of the glutamate in iLOV-Q430E points away from the flavin cofactor, which leads to a future expectation that further red shifting may be achieved by bringing the side chain closer to the cofactor.

Absorption Spectrum and Raman Spectroscopy of Coumarin507 Dye Laser in Different Solvents

Coumarin dye laser compounds are often used as components in coloring agents and sprays., as well as in the odorization of foods. Therefore, the important of these compounds in many felids leading to growth of several ways aiming to advance the control of pharmaceutical and superficial producing. Solvents play an important role in changing the character of coumarin. The investigated spectral properties, as well as the effect of changing the solvent on this property, have been published. results referred that the molar electronic transition energy increased with decreasing the maximum absorption wavelength, and the highest intensity of the absorption spectrum was in the case of acetone solvent. In addition, many bands appear in Raman shift attributed to the ''C=O'' band, ''O=C–O, C–C'', and ''C–O'' deformation. The characteristic vibrations involving the ''O-H'' group is the stretching and bending modes of the ''O-H'' and ''C-O'' parts.

Investigation of Consequences of High-Voltage Pulsed Electric Field and TGase Cross-Linking on the Physicochemical and Rheological Properties of Pleurotus eryngii Protein.

This study aimed to evaluate the effects of high-voltage pulsed electric fields (HPEF) and transglutaminase (TGase) cross-clinking on the physicochemical and rheological properties of Pleurotus eryngii protein (PEP). The results showed that HPEF increased α-helixes and β-turns but decreased β-folds. A HPEF at 1500 V/cm maximized the free sulfhydryl content and solubility of PEP. TGase formed high-molecular-weight polymers in PEP. TGase at 0.25% maximized the free sulfhydryl groups, particle size, and solubility; shifted the maximum absorption wavelength from 343 nm to 339 nm and 341 nm; increased α-helixes and β-turns and decreased β-folds; and showed better rheological properties. Compared with TGase cross-linking, HPEF-1500 V/cm and 1% TGase significantly reduced the free sulfhydryl groups, particle size, and solubility, produced more uniform network structures, and improved the rheological properties. These results suggest that HPEF can increase the cross-linking of TGase and improve rheological properties of TGase-cross-linked PEP by affecting the physicochemical properties.

Fluorinated Merophosphinine and Phosphinine Dyes: Synthesis and Evaluation of UV-Visible Light Absorption Properties

Merophosphinine and phosphinine dyes were reported as phosphorus atom equivalents of merocyanine and cyanine dyes in the 1960s. Although these dyes are excellent sensitizers for enhancing photographic performance, their development has been considerably retarded because of difficulties in the synthetic process. Previously, while investigating the reactivity of fluoroalkenes with various nucleophiles, we developed fluorinated merophosphinine and phosphinine scaffolds in a single reaction step; however, we did not investigate their ultraviolet-visible (UV-vis) light absorption properties further. Therefore, in this study, we synthesized fluorinated merophosphinines and phosphinine derivatives using triphenylphosphonium ylides with various R substituents [R = H, C6H5, 4-MeOC6H4, 4-PhC6H4, or C6F5] and octafluorocyclopentene to study their absorption characteristics. Thermogravimetric analyses (TGA) indicated that several synthesized derivatives were thermally stable at temperatures above 241 °C. Additionally, when studied in various solvents, the fluorinated merophosphinine and phosphinine dyes exhibited well-defined maximum absorption wavelengths (λabs) in the 364–375 and 420–474 nm ranges, respectively. Thus, fluorinated merophosphinine and phosphinine derivatives may serve as promising thermally stable functional dyes for future technical applications.

Development and validation of UV-spectrophotometric method for estimation of pterostilbene in Pterocarpus marsupium

Aim: To develop and validate a simple, precise and cost effective UV-visible spectrophotometric method for the estimation of pterostilbene in Pterocarpus marsupium extract. All the parameters of the analysis were chosen as per ICH Q2 (R1) guideline. Methods: Pterostilbene solution was scanned over UV-visible range for its wavelength of maximum absorbance. Various calibration standards of pterostilbene were prepared. Calibration curve of concentration vs. absorbance was plotted and developed UV – visible spectrophotometry method was used for estimation of pterostilbene in standardized Soxhlet assisted extract (SAE)as well as ultrasound assisted extracts (UAE) of Pterocarpus marsupium. Results: The maximum wavelength of pterostilbene was found to be 306 nm. The correlation coefficient of developed UV-Visible spectrophotometric method over the concentration range of 1-6 μg/ml was found to be 0.999. The validation study of the said method was carried out in terms of linearity, accuracy, precision, robustness, ruggedness, limit of detection and limit of quantitation studies. Developed UV – visible method was found to be precise for the intra- and inter- day studies and showed standard deviation in the range of 0.83 to 1.912&amp;0.762 to 1.542respectively. The pterostilbene content in Pterocarpus marsupium extract was found to be 4.5% using the proposed UV – visible spectrophotometry method. Conclusion: A simple, precise and cost-effective UV- visible spectrometry method was developed for the estimation of pterostilbene in standardized extract of Pterocarpus marsupium. The method was developed using solvent containing economical percentage of organic phase in aqueous media. Said validated UV- visible method can be efficiently used for the estimation of pterostilbene in extracts of Pterocarpus marsupium.

Application of zinc oxide nano-tube as drug-delivery vehicles of anticancer drug

Zinc oxide nano-tube (ZnONT) nano-structures, which possess chemical stability and non-toxicity in the human body, are considered promising for delivering different drugs. Within this work, we scrutinized the drug delivery capability of the ZnONT and its adsorptional properties as a drug delivery vehicle (DDV) for hydroxyurea (HU) as an anti-cancer drug through density functional theory along with the solvent impacts. Based on the optimized structures, it can be suggested that Zn atoms of ZnONT are the ideal sites on this nano-tube for the adsorption of HU. HU had a strong physical adsorption through the O atom of carbonyl groups onto the local pyramidal site of the ZnONT. At 1.96 Å and Ead of -39.28 kcal/mol, in the configuration which was favorable in terms of energy, there was an interaction between the O atoms of -C=O group of the drug and a Zn atom of the ZnONT. In order to scrutinize the excited state properties of the HU-ZnONT complex, we also examined the UV/Vis data of the HU/ZnONT interaction system. Following the adsorption of HU onto the surface of the ZnONT, there was a significant red-shift based on the maximum absorption wavelength, showing that the ZnONT is an ideal candidate for optic sensors in order to detect and monitor the drug molecule. HU could be released in the cancer tissues where pH was low based on the drug release mechanism. The current work thoroughly investigated the mechanism of interaction between the ZnONT and HU, showing that ZnONT can be used for the smart drug delivery of HU. Overall, the findings suggest that ZnONT could be used as an efficient drug-delivery system for the HU drug to treat various types of cancer. In this work we used B3LYP-gCP-D3 functional and the basis set LANL2DZ on the transition metal (Zn) and the basis set cc-pVDZ on the others. GAMESS software program was employed for performing the calculations. we performed analyses, including charge transport, molecular electrostatic potential surface (MEP), energetic, electronic, natural bond orbitals (NBOs), and structural optimizations.

Spectral and biodistributional engineering of deep near-infrared chromophore

Fluorescence-guided surgery calls for development of near-infrared fluorophores. Despite the wide-spread application and a safe clinical record of Indocyanine Green (ICG), its maximal absorption wavelength at 780 nm is rather short and longer-wavelength dyes are desired to exploit such benefits as low photo-toxicity and deep penetration depth. Here, we report ECY, a stable deep near-infrared (NIR) fluorochromic scaffold absorbing/emitting at 836/871 nm with a fluorescence quantum yield of 16% in CH2Cl2. ECY was further rationally engineered for biological distribution specificity. Analogous bearing different numbers of sulfonate group or a polyethylene glycol chain were synthesized. By screening this focused library upon intravenous injection to BALB/c mice, ECYS2 was identified to be a suitable candidate for bioimaging of organs involved in hepatobiliary excretion, and ECYPEG was found to be a superior candidate for vasculature imaging. They have potentials in intraoperative imaging.

Designing and Theoretical Study of Dibenzocarbazole Derivatives Based Hole Transport Materials: Application for Perovskite Solar Cells.

Hole-transporting materials (HTMs) are essentials in producing the efficient and stable perovskite solar cells (PSCs). In this article, we provided the investigation results of electronic structures and photophysical characteristics of eight designed derivatives (HTM1a-HTM4a and HTM1b-HTM4b) of a dibenzocarbazole-based compound HTMR. HTMR was modified by substituting the terminal groups located on the diphenylamine moieties with two and four electron donor groups (ED1-ED4) of different character. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) have been used to optimize the geometry of the ground state and for excited state calculations, respectively. The nature and number of electron donor substitutions on the frontier molecular orbitals (FMOs), ionization potential (IP), electronic affinity (AE), maximum absorption wavelengths ([Formula: see text], solubility ([Formula: see text], stability (η), exciton binding energy ([Formula: see text], reorganization energies ([Formula: see text] and charge mobility (k) are examined and discussed in detail. On this basis, the features such as proper HOMO levels (-5.464 and -4.745eV), comparable hole mobilities ([Formula: see text] (4.632 × 1013 and 1.177 × 1014s-1), a significant [Formula: see text] (367.13 and 398.27nm), and high η (1.440 and 1.667eV) have made these structures suitable hole transport materials (HTMs) to provide perovskite solar cells with a high efficiency.

Synthesis of fluorescent chalcones, photophysical properties, quantitative structure-activity relationship and their biological application

The development of fluorescent pigments is an area of interest in several research fields due to their high sensitivity. In the current study-eight known and three new N,N-dimethylamino-chalcones (12a-k) were synthesized with good yields using the Claisen-Schmidt reaction. For each molecular system, the photophysical properties, including the maximum absorption wavelength (λAbsorption), molar absorption coefficient (ε), maximum excitation wavelength (λExcitation), maximum emission wavelength (λEmission), Stokes Shift (Δλ), fluorescence quantum yield (Φfl), fluorescence lifetime (τfl), radiative and non-radiative rate constants (kR and kNR, respectively) were evaluated. Variations in each of these properties were analyzed depending on the substituents present on each compound. To relate the chemical structures of the synthesized compounds to their photophysical properties, Hansch analysis (2D-QSPR) was applied. As a result of Hansch analysis, we found different photophysical properties related to molecular orbitals and the energy of their derivatives (Highest Occupied Molecular Orbital-HOMO, Lowest Unoccupied Molecular Orbital-LUMO, Difference between LUMO-HOMO-ΔLH, Chemical potential-µ, Hardness-η, Softness-S, and electrophilic global index-ω) as well as to the atomic charges on atoms C5, Cα, Cβ, and CO. The application of this type of analysis has made it possible to understand and subsequently design new molecules with defined photophysical properties. Finally, the compounds were use as fluorescent pigment to get living cell imaging on breast cancer cells, obtaining the compound 12a as promissory alternative.

Textile-Based Volatile Organic Compound Sensors Using Cellulose Fabrics and Direct Dyes

ABSTRACT In order to fabricate colorimetric textile sensors detecting gas phase of volatile organic compounds (VOCs), 11 kinds of direct dyes were investigated for 13 types of VOCs. Direct Violet 51 was chosen for its best sensing performance both instrumentally and visibly. Direct Violet 51 exhibited the change of color strength and color hue by exposure VOCs. The dyed cotton fabrics detected polar VOCs well, especially N,N-dimethylformamide (DMF). The colorimetric cotton-based textile sensor dyed with Direct Violet 51 exhibited approximately 10 of color difference (ΔE) under 10 ppm DMF gas within 100 min, and the maximum absorption wavelength was shifted from 560 nm to 530 nm. The sensing mechanisms could be summarized in three factors: solvatochromism and aggregative characteristics from the point of view of dye, and adsorption amount of VOCs for fabric. The colorimetric textile sensor retained its sensing performance after 10 cycle tests.

Surfactant catalyzed electron transfer mechanism in the oxidation of racemic tartaric acid by Ce(IV)

Oxidation of α-hydroxy acid, racemic tartaric acid and its kinetic studies have been carried out to establish the mechanism of oxidation. The electron transfer reaction was performed in presence of surface active agents, surfactants, a clean and green catalytic material, using Ce(IV) as the oxidant. The progress of the reaction was monitored using a spectrophotometer by recording the fall in absorbance of Ce(IV) at its λ max (wave length of maximum absorbance) of 380 nm. Disappearance of Ce(IV) is observed to be first order at constant [H + ]. Plot of log(Absorbance) against time is found to be linear in the initial stages of the reaction. The results of oxidation rates show a complex dependence of rate on [H + ]. The pseudo first order rate constants ( k ) obtained with varying substrate concentration and the plot of k obs /[substrate] vs [substrate] are observed to be excellently linear with positive slope. Plots of pseudo first order rate constants in presence of surfactant (sodium dodecyl sulphate, SDS) against the [SDS] abruptly rises in the concentration range below cmc (critical micelle concentration) after which the rate exponentially falls. Based on all the findings, Berezin model has been advanced to explain the observed kinetic phenomenon in the surfactant medium.

Computational study of new pyranylidene-based D-π-A-A dyes: Effect of the change of the auxiliary acceptor

In this study, four D-π-A-A molecules, based on pyranylidene as the donor, were developed by modification of the auxiliary acceptor. These molecules were theoretically studied using DFT and TD-DFT methods. The optoelectronic and photovoltaic properties were calculated as HOMO, LUMO, Egap, VOC (the open-circuit photovoltage), λmax (the maximum absorption wavelength), Eex (the vertical excitation energies), f (the oscillator strengths) in order to study the effect of auxiliary acceptor change on the enhancement of light absorption capabilities and increase of intramolecular charge transfer ICT. The findings indicate that the D4 dye performs better than the rest of the dyes as it is characterized by a low energy gap (Egap=1.549 eV) and a maximum wavelength (λmax=758 nm). Therefore, the D4 dye is a good candidate for use as a DSSC sensitizer.