Spectra Of Dyes Research Articles

Structure design of light-resistance fluorane dyes and preparation of color changing materials

Fluorane dyes were widely applicated in the thermochromic area, especially in the form of smart textiles, as they could adjust color via electron transfer. However, developing perfect bright color and light-resistance fluorane dyes had remained challenging due to the intrinsic structural limitations. Here, we reported a series of new fluorane dyes with different electron withdrawing groups that controlled the electron cloud density of the lactone ring, which enhance the thermochromic stability and light-resistance properties. The red shift or blue shift of the absorption wavelength, which could broaden the dye's spectrum, was controlled by the number of electron-absorbing substituents. Moreover, fluorane dyes with a withdrawing group introduced at the R3 position of the lactone ring had excellent light-resistance ability, which was 66%∼57.2% lower than that of commercial dye after 14 h of light irradiation. But, the excess substituents would have weakened its original light-resistance. We also explain the photostability associated with the electron distributon using Density Functional Theory (DFT) simulation. This achievement in the development of light-resistance fluorane offers a promising solution for the application of color-changing materials with a broad absorption spectrum and light-resistance.

Spectrophotometric and conductometric studies on the interaction of surfactant with polyelectrolyte in the presence of dye in aqueous medium

The concentration of methyl red (MR) dye has a significant influence on how the CTAB + NaPSS complex (CTAPSS) aggregates and sticks together. However, the effect of MR dye on CTAPSS has not yet been thoroughly investigated. The major goal of this work is to use conductometry and UV–Vis. techniques to investigate the influence of MR on the interactions between a cationic surfactant, cetyltrimethylammonium bromide (CTAB) and an anionic polyelectrolyte, sodium polystyrene sulfonate (NaPSS) in aqueous environments. By observing changes in the dye's spectra and the breaking points of conductometric curves, it is obvious that MR causes the development of surfactant aggregates. Critical aggregation concentration (CAC), apparent critical micelle concentration (CMC*), ionization degree (α), binding constant, and various other important thermodynamic parameters were determined by conductivity techniques at 298.15 ± 0.2 K. The CAC and CMC* values dropped on raising the concentration of CTAB with MR in the CTAB + NaPSS + MR system, which is caused by the substantial electrostatic interactions between CTAB/NaPSS and MR. With anionic MR, aggregation and micellization become easier, as seen by hypsochromic shift and reduction in the absorption band's intensity. With increasing CTAB concentrations, the absorption spectra of MR were observed between 430 and 440 nm for the basic form steadily dropped to 414–421 nm. The Benesi-Hildebrand equation was used to calculate the binding constants from the absorption spectra of MR. The CMC of CTAB in water was determined to be 0.00091 molL-1 but the CMC* of CTAB for the CTAB + NaPSS system was determined to be 0.001438 molL-1 and CMC* for the CTAB + NaPSS + MR system was observed to be 0.001328 molL-1 by conductivity and 0.001310 molL-1 by UV–Vis. spectroscopy at 298.15 ± 0.2 K. Also, it is observed that CMC* obtained by spectroscopy is slightly lower (0.001310 mol L-1) than those obtained from conductometry (0.001328 mol L-1) since the spectrum is extremely sensitive for molecular interactions and their properties.

Lasing Spectra of Dye Doped Cholesteric Liquid Crystals Under Reversible Phototuning of the Frequency

We investigate the lasing frequency phototuning in a distributed feedback (DFB) laser based on cholesteric liquid crystals (CLC). To improve the CLC planar texture quality, we use new materials such as nematic ZhK-654 and an analog of cholesteryl oleate as a twisting additive. The selective excitation of the cis-form molecules of the azoxy-nematic is carried out with the use of a combination of an interference filter with maximum transmission at 436 nm and a cut-off filter. Using the orienting substrates with SnO2 allows us to reduce the threshold pump power by more than an order of magnitude. The proposed combination of filters for the selective excitation enables us to align the ranges of lasing wavelengths in both directions.

Indirect Determination of Oxidant Concentration Using Resonance Raman Spectra of Dyes

Many problems in modern chemical analysis require specialized methods with very high sensitivity. The development of more sensitive and specific methods of analysis is the pressing goal of both analytical chemists and instrument manufacturers. Vibrational spectra are a valuable source of specific information about a molecule, but classical IR and Raman spectrometer have been hindered by relatively low sensitivity. Sensitivity has been enhanced recently by improvements in and applications of electronics, lasers, and computers. Use of Resonance Raman (RR), even with conventional Raman instrumentation, can increase the sensitivity by as much as 103 to 104 times that observed with the normal Raman effect. The increased sensitivity of resonance Raman results in a detection limit for the Raman spectra on the order of that obtained from the electronic spectrum of the molecule.

The interaction of tetraiodofluorescein with creatine kinase

The dye 2′,4′,5′,7′-tetraiodofluorescein is a potent inhibitor of creatine kinase (ATP:creatine N- phosphotransferase , EC 2.7.3.2) with an apparent competitive inhibition constant with respect to MgATP 2− of 2.6 · 10 −5 M . The association of the dye with the enzyme elicited a red shift in the dye's spectrum, indicative of a binding site less polar than water. The dye binds to the enzyme with an equilibrium constant of dissociation of 1.7 · 10 −5 M . MgATP or MgADP competes for the dye-binding site. Creatine binds to creatine kinase-tetraiodofluorescein complex to form a ternary complex and further causes a blue-shift in the spectrum of the bound dye. The binding of the dye to fully active creatine kinase causes conformational change that was monitored by enzyme-bound 2-mercuri4-nitrophenol, a conformation-dependent “reporter group”.