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Merits of Selecting Metal-Organic Frameworks as Sensors
Published in Ram K. Gupta, Tahir Rasheed, Tuan Anh Nguyen, Muhammad Bilal, Metal-Organic Frameworks-Based Hybrid Materials for Environmental Sensing and Monitoring, 2022
Harmeet Kaur, Amit L Sharma, Akash Deep
Intramolecular charge transfer (ICT) is the process of tuning emission intensity as well as wavelength through the electron process. Both electron donating and electron accepting groups contribute to ICT. With the presence of both groups on a molecule, dipoles are formed. In the excited state, in the presence of different solvents and operating conditions, the dipole moment varies followed by the change in luminescence. Different environmental contaminants and solvents like toluene, chloroform, isopropanol have been sensed using ICT-based luminescence quenching [34]. Color change is one of the most basic means of sensing any phenomenon. Solvatochromism is the shift in absorption wavelength of material upon change of solvent and the shift is correlated with the polarity of the solvent. Blue shifting of absorption band has been reported in the case of Cu-MOF upon the shift of solvent from low to high polarity (water to chloroform) [35]. Apart from the solvatochromic effect, solvent-dependent color changes in MOF absorption have also been ascribed to changes in coordination environment, for example, change in absorption of Co-MOF upon absorption of different vapors due to change in geometry from octahedral to tetrahedral [35].
Polymeric Second-Order Nonlinear Optical Materials and Devices
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
As explained earlier, molecular hyperpolarizability of an NLO chromophore is due to the presence of low-lying electronic states resulting in strong intramolecular charge transfer. The intramolecular charge-transfer transitions of chromophores, thus the absorption spectra, are very sensitive to the polarity of their environment. NLO chromophores are said to be solvatochromic. Solvatochromism is a change in absorption spectrum (λmax, intensity, and shape) of a chromophore in solvents of different polarity even in solid solutions. Positive (bathochromic) solvatochromism refers to a redshift of the absorption band with increasing solvent polarity. Polar solvents stabilize the excited state with charge separation and polarity of a solvent can be determined by its solvation behavior, which in turn depends on the intermolecular forces between the solvent and the solute. Thus, the solvatochromism can be used to determine hyperpolarizability as mesomeric dipole moments, the variation of the molecular dipole moment with excitation. Solvatochromism of dipolar NLO chromophores can be measured to estimate and compare β chromophores qualitatively within closely related structures [19]. Other more quantitative experimental methods to determine the β of chromophores such as electric field-induced second harmonic generation (EFISH) and hyper-Rayleigh scattering (HRS) measurements were discussed in earlier chapters. The molecular structures of representative examples of dipolar NLO chromophores are shown in Figure 16.3, and the molecular hyperpolarizabilities of the chromophores are summarized in Table 16.1.
Infrared Attenuated Total Reflection Spectroscopy of Surface Active Species
Published in Arthur T. Hubbard, The Handbook of Surface Imaging and Visualization, 2022
Roger P. Sperline, Henry Freiser
ATR is not confined to the infrared. With suitable chromophores (e.g., functionalized aromatic compounds), UV-Vis ATR is possible20 and may be advantageous when there are interferences in the IR. UV-Vis probes, for example, the pyridinium betaine dye Et30, are potentially more sensitive to solvation changes than IR probes. A change in spectral band position with solvent is called “solvatochromism.”
Rod-shaped cyanoacrylic derivatives with D-π-A architecture: synthesis, thermal, photophysical and theoretical studies
Published in Liquid Crystals, 2023
Caroline S. B. Weber, Aline Tavares, Bruno Bercini de Araújo, Rebeca O. Costa, Taise M. Manhabosco, Bruna B. Postacchini, André A. Vieira, Thiago Cazati, Aloir A. Merlo
For the naphthyl derivative, a hypsochromic shift was observed in the maximum emission in heptane (429 nm), toluene (483 nm) and THF (516 nm), (less polar solvents) compared to chloroform. In contrast, using a more polar solvent such as acetonitrile (542 nm) or acetone (524 nm), a bathochromic shift in the maxima emission was registered. A large Stokes shift was observed by the variation of the solvent (48–178 nm) to 5. A similar trend was observed for 4. The strong displacement produced by the solvent in the fluorescence of the samples can enable these materials as solvatochromic probes [32]. The solvent-sensitivity of a fluorophore can be estimated using the Lippert-Mataga equation [33]. A plot was constructed for dyes 4 and 5 (Figure 4) where the energy difference expressed in wavenumbers (cm −1) between the ground and excited states (νAbs - νEm, Stokes shift) is plotted against solvent orientation polarisability (Δf). In a classic solvatochromic dye, the dependence of a Stokes shift on Δf is linear in the absence of solvent-specific interactions, and the slope of the plot reflects solvatochromic sensitivity of the sample.
Synthesis and characterization of novel fluorescent reactive dyes for dyeing of cotton fabrics
Published in The Journal of The Textile Institute, 2022
Maral Pishgar, Kamaladin Gharanjig, Mohammad Esmail Yazdanshenas, Khosro Farizadeh, AboSaeed Rashidi
The synthesized dyes have been dissolved in different solvents with various dielectric constants for studying the solvatochromism effect. The UV-visible absorption of each synthesized dyes was obtained in different solvents such as water, DMF, and methanol at 5 10−6 mol/L concentration and reported in Table 2 and Figure 1. The maxima absorption wavelength of dyes in different solvents was 488–496 nm in the visible area. The results indicated that the dyes had the highest absorption maxima wavelength in polar solvents. The dyes were dissolved in water because of the presence of sulfone groups in their structures; hence, they are polar dyes. The absorption wavelength shifts in solvents related to the dielectric constant of solvents and the interaction of dyes and solvents. The molecule is more non-polar in the ground state than an excited state. In the excited state, the molecule becomes more polar and more stable in polar solvents. Therefore, the solvatochromism effect is positive.
Smart textiles: an overview of recent progress on chromic textiles
Published in The Journal of The Textile Institute, 2021
Heloisa Ramlow, Karina Luzia Andrade, Ana Paula Serafini Immich
Spectrophotometric investigation of the dyes in different solvents is examined in order to obtain their absorption maxima and solvatochromic effects. Solvatochromic shifts occur due to an energy gap between a ground state and excited state of different polarities since the change in solvent polarity leads to variance stabilization of these electronic states. Therefore, specific interactions between chromophore and solvent molecules lead to variations in the wavelength shape of the absorption and of the extinction coefficient values (Jeong et al., 2018).