179 documents found, page 1 of 18
Solvatochromism and cis-trans isomerism in azobenzene-4-sulfonyl chloride
Sidir, Isa; Gülseven Sidir, Yadigar; Berber, Halil; Fausto, RuiSolvatochromism exhibited by azobenzene-4-sulfonyl chloride (here abbreviated as Azo-SCl) has been investigated in a series of non-polar, polar-aprotic and polar-protic solvents. The UV-vis spectra of Azo-SCl exhibit two long-wavelength bands, observed at 321-330 nm (band-I) and 435-461 nm (band-II), which are ascribed to the π*-π (S2←S0) and π*-n (S1←S0) transitions, respectively. The shorter wavelength band i...
A comprehensive exploration of optical properties of GdAlO3: Cr3+
Souissi, Hajer; Kammoun, S.; Dhahri, E.; Pina, João; Costa, Benilde F. O.; Fausto, RuiThis study focused on the optical properties of the Cr3+-doped GdAlO3 perovskite,through comprehensive analysis of its photoluminescence spectra. The GdAlO3:Cr3+perovskite,synthesized by a traditional solid-state process, crystallizes in theorthorhombicPbnmspacegroup, with Cr3+ions substituting Al3+ ions in octahedral sites. Photoluminescence excitation and emission spectra of the material were obtained and ass...
Co-doped FeNbO4: Simple synthesis, DFT calculations and electrocatalytic perfor...
Jucá, Raí F.; Evaristo, Diego S.; Oliveira, Francisco G. S.; Santos, Luís P. M.; Saraiva, Gilberto D.; Castro, António J. R.; Ferreira, Nilson S.Cobalt-doped iron niobate samples, Fe(1−x)CoxNbO4 (0 ≤ x ≤ 0.20), synthesized by the solid-state reaction method, were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Density functional theory (DFT) calculations was employed to assign the experimental Raman modes of FeNbO4 and for cobalt-doped iron niobate, as the Rama...
Novel tetradentate N2O2 water-soluble Schiff Base and its Al(III) complex: synt...
Bouznif, Hajer; Justino, Licínia L. G.; Soares, Maria I. L.; Costa, Telma; Ramos, Maria Luisa; Nikitin, Timur; Pinho e Melo, Teresa M. V. D.A novel water-soluble di-Schiff base, N,N’-bis(3-methoxy-5-sulfonatosalicylidene)-1,2- ethylenediamine disodium salt (MSS), was synthesized under both conventional heating and microwave-assisted conditions. Detailed characterization was conducted using various techniques including NMR, HRMS, UV_vis, SEM/EDX, DSC, ATR-FTIR and Raman spectroscopies, accompanied by DFT calculations. The study discusses the enol-im...
Infrared Spectrum and UV-Triggered Transformations of Matrix-Isolated Meta-Fluo...
Lopes Jesus, António J.; Lucena, Juracy R. Jr.; Rodrigues, G. P.; Ogruc Ildiz, Gulce; do Monte, Silmar A.; Ventura, Elizete; Fausto, RuiThe infrared (IR) spectrum of meta-fluorothiophenol (mFTP) isolated in a low-temperature N2 matrix was recorded and interpreted with the aid of B3LYP vibrational frequency calculations for both cis and trans conformers. Then, photochemical transformations in the matrix-isolated compound were triggered through UV-Vis laser irradiations and their outcomes were monitored by IR spectroscopy. Upon excitation at λ = ...
A protocol for the investigation of the intramolecular vibrational energy redis...
Duarte, Leonardo J.; Nunes, Cláudio M.; Fausto, Rui; Braga, Ataualpa A. C.The conformational isomerization of nitrous acid (HONO) promoted by excitation of the νOH or νN[double bond, length as m-dash]O stretching normal coordinates is the first observed case of an infrared-induced photochemical reaction. The energy captured by the excited normal modes is redistributed into a highly excited vibrational level of the τOH torsion normal coordinate, which is the isomerization reaction coo...
A thermodynamic journey: unlocking cold thermal energy storage with phase equil...
Sequeira, Maria Carolina; Nikitin, Timur; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João; Fausto, RuiAs the urgent demand for sustainable energy solutions increase, thermal energy storage (TES) systems have become crucial in improving energy efficiency and ensuring supply-demand balance. For low-temperature areas such as refrigeration, cold-chain logistics, and specific medical applications, phase change materials (PCM) are particularly valuable due to their high latent heat capacity and reversible phase trans...
Solid-liquid phase diagram of the dimethyl + dipropyl adipates system: applicat...
Sequeira, Maria Carolina; Nikitin, Timur; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João; Fausto, RuiThe present study is the continuation of our research work on di-n-alkyl adipates and their potential as phase change materials (PCM) for low-temperature thermal energy storage (TES). The solid–liquid phase diagram for the binary system composed of dimethyl adipate (DMA) and dipropyl adipate (DPA) is presented and analysed. In a previous study, we explored a particular binary system of n-alkyl adipates, namely ...
Tuning thermal performance: the role of molecular asymmetry in di-n-alkyl adipa...
Sequeira, Maria Carolina; Nikitin, Timur; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João; Fausto, RuiThe development of efficient and sustainable thermal energy storage (TES) systems is crucial for improving energy efficiency in various applications, especially at low temperatures, such as cryogenic cooling, cold storage, logistics and transportation. Phase change materials (PCM) play a key role in TES, as they allow the storage and release of significant amounts of latent heat during phase transitions. In thi...
Enhancing low-temperature thermal energy storage with next-generation PCMs
Sequeira, Maria Carolina; Nogueira, Bernardo; Nikitin, Timur; Diogo, Herminio; Caetano, Fernando J. P.; Fareleira, João; Fausto, RuiThe communication reports the potential use of PCM, n-alkanes and n-alkyl adipates, at low temperatures (between -80 ºC and -20 ºC) for different applications in the cold chain logistics such as the transport of medicines. For the phase equilibrium studies, of the different mixtures, techniques as differential Scanning Calorimetry (DSC), Hot-stage Polarized Microscopy and Raman Spectroscopy were used.