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The results presented here refer to the tunability of global emission characteristics of Eu3+, Dy3+ and Eu3+/Dy3+ ions, varying the composition glasses; TeO2-GeO2-X (X = ZnO, MgCl2). Also, the influence of exchanging the modifier compound on the global luminescent response of the glasses was analyzed by Raman spectroscopy, excitation and emission spectra, and emission decay profiles. Changes in the Te-O-Te network structure, when MgCl2 substitutes ZnO, were identified from Raman spectrum deconvolution analysis. The energy transfer between Eu3+ and Dy3+ ions, and tunable emission characteristics, were studied under UV excitations that correspond with the emission of InGaN (370–420 nm) based LEDs. The energy transfer process between Eu3+ and Dy3+ ions was studied based on the emission spectra with different excitation wavelengths and time decay curves of the 5D0→7F2 level of Eu3+ at 612 nm. In TGZED and TGMED glasses and upon 351 nm, the time shortening of Dy3+ emission decay in presence of Eu3+ was attributed to an Dy3+→Eu3+ non-radiative energy transfer process. The energy transfer probabilities PD→E and energy transfer efficiency ηD→E were calculated for TGZ and TGM glasses. According to the Inokuti-Hirayama model it might be dominated through an electric dipole-dipole interaction, with efficiency of 5.0% and 1.9% and the obtained γ6 energy transfer parameter values γ6 = 0.082 ± 0.005 and 0.026 ± 0.005 respectively, for TGZED and TGMED glasses. The non-radiative Eu3+→Dy3+ energy transfer was observed too for both glasses TGZED and TGMED, so that transfer of energy is more favored in the oxide vitreous matrix than in the oxide-halide one. The dominated are an electric dipole-dipole interaction with γ6 energy transfer parameter values are 0.072 ± 0.005 (TGZED) and 0.036 ± 0.005 (TGMED), with efficiency 6.9 and 4.1% respectively. In TGM glasses is very low efficiency of non-radiative Dy3+→Eu3+ and Eu3+ →Dy3+ energy transfer that TGZ matrix. Neutral white emissions of 4135, 4567 K were observed in the Dy3+ and 3914 and 242 K, Eu3+/Dy3+ doped TGZ glasses excited at 351 and 388 nm, respectively. Similarly, global emissions of Dy3+ single doped were 4028 and 4123 K, but in Eu3+/Dy3+ double doped TGM glasses are neutral white light of 3929 and 3979 K, respectively. Upon 394 nm excitation, the Eu3+ doped TGZ and TGM glasses displayed reddish-orange global emissions of 1979 and 1964 K, respectively. For excitations at 382 and 394 nm the Eu3+/Dy3+ doped TGZ and TGM glasses emit warm white light of 3414 and 3160 K (382 nm excitation) and reddish-orange of 2123 and 2030 K (394 nm excitation), respectively, depending mostly on the Eu3+ and Dy3+ relative excitation intensity.

The TeO2–TiO2–ZnO glass was single doped with Er3+ and its structural, luminescent, and upconversion properties were analyzed. The amorphous nature of the fabricated glass was confirmed by X-ray diffraction, and the characteristic vibrational modes of the tellurite-titanium-zinc glass network were identified by Raman spectroscopy. The photoluminescent and upconversion properties of Er3+ doped glass was analyzed by time decay measurements at different excitation wavelengths. The spectra recorded upon excitations at 808 nm and 975 nm show an intense green upconversion luminescence corresponding to the 2H11/2, 4S3/2 → 4I15/2 transitions and a very weak red emission associated to the 4F9/2 → 4I15/2 transition. The experimental results suggest that in Er3+ doped glass the excited state absorption and/or energy transfer mechanisms are responsible for upconversion luminescence observed upon 808 nm and 975 nm excitations.

Single-crystal X-ray diffraction (SCXRD) experiments and theoretical calculations based on the Quantum Theory of Atoms in Molecules (QTAIM) approach have been used to analyse the characteristics of the covalent and the non-covalent interactions of 2,4-dinitrodiphenylamine (2,4-dna), also known as Serisol-Yellow 2G. DSC-TGA experiments were also carried out to obtain data on the thermal stability of the entitled compound. SCXRD and QTAIM results showed that 2,4-dna molecules form centrosymmetric dimers linked by unusual O⋯O intermolecular interactions with short contact distances (2.73 A) that are accompanied by C H⋯O and N H⋯O intermolecular interactions. Due to the number of -CH groups available in 2,4-dna, the molecular self-assembly continues through C H⋯O intermolecular interactions, which also contribute with the stabilization of the supramolecular network. The analysis of the ESP map revealed that the most positive region of the -CH groups bound to the most negative -NO2 group forming a R 2 2 ( 7 ) synthon. DSC-TGA analysis revealed that 2,4-dna is stable up to 150 °C.

The long persistent luminescence, thermoluminescence (TL) and IR stimulated luminescence properties of two orthorhombic strontium aluminates (Sr4Al14O25) co-doped with Eu2+, Dy3+ and Eu2+, Nd3+ exposed to beta radiation is reported. The phosphors were synthesized by the combustion method followed by a post-annealing treatment under a reductive carbon atmosphere. Photoluminescence emission spectra of both phosphors are typical for emission of Eu2+ ions with 7-fold and 10-fold coordination in Sr4Al14025 and consist of the main band at 480 nm and a weak band between 390 and 440 nm. After exposure to beta radiation the Sr4Al14025:Eu2+,Dy3+ phosphor exhibits two strongly overlapped TL peaks at about 70 and 100 °C while the low temperature TL of the Sr4Al14025:Eu2+,Nd3+ phosphor consist of two well separated peaks with maxima at about 60 and 130 °C. Additionally, both phosphors exhibit a weak TL between 180 and 400 °C. The traps responsible for the low temperature TL peaks are the Dy3+ and Nd3+ centers situated in two different Sr sites with 7-fold and 10-fold coordination. The thermal emptying of the Dy and Nd filled traps creates ultra-long intense afterglow, which gradually decays with time and remains detectable after 220 h storage in dark. IR stimulation of beta irradiated phosphors creates intense IR stimulated luminescence, which is related to the release of electrons from the filled Dy and Nd traps.

In this work, we report an analysis of the molecular structure and the hydrogen-bonding patterns in the crystal structures of 5-methoxy-2-nitroaniline (1) and 5-methoxy-2-nitroaniline with 2-amino-5-nitropyridine (1:1) co-crystal (2). X-ray single crystal diffraction experiments were carried out to analyse the intermolecular forces in terms of geometrical criteria. These intermolecular interactions were also investigated through topological analysis of the electron density (ρ) employing QTAIM and NCI methods. Additionally, Raman spectroscopy was employed to analyse the vibrational characteristics of the entitled materials. The supramolecular structure of (1) is produced by crosslinked chains, which are primarily dominated by N-H···O hydrogen bonds. However, C-H···O interactions reinforce this connectivity. Furthermore, the molecules in (1) are connected through two-centre instead of the three-centre hydrogen-bonding interactions between the -NH2 and -NO2 groups commonly observed in nitroanilines. The asymmetric unit of (2) contains two symmetry-independent molecules of 5-methoxy-2-nitroaniline (5M2NA) and two symmetry-independent molecules of 2-amino-5-nitropyridine (2A5NP). The supramolecular structure of (2) is developed not only for N-H···O but also N-H···N and supportive C-H···O hydrogen bonds. The two symmetry-independent 2A5NP molecules bound to each other through two-centre hydrogen bonds between the -NH2 and -NO2 groups forming C 2 2 ( 16 ) chains. 5M2NA molecules bound to these chains forming R 2 2 9 and R 2 2 ( 8 ) synthons. Experimental and theoretical results obtained in this work suggest that C-H···O interactions play an important role in the stabilization of these supramolecular structures.

Zinc oxide nanorods decorated with gold nanoparticles were deposited on an optical fiber and were used for carbon dioxide gas detection at room temperature. This optical gas sensor is based on the changes in the intensity of transmitted light due to the interaction of gas molecules with zinc oxide surface. Zinc oxide nanorods were prepared by ultrasonic method and were decorated with spheroidal 20 nm gold nanoparticles. Sensing experiments were carried out using two different wavelengths. The sensor can respond to a CO2 atmosphere and recover to its original state once the gas is removed, showing a better response when red light is used. Moreover, it responds almost linearly with concentration until 2000 sccm. The incorporation of gold nanoparticles greatly reduces the sensitivity of the sensor and increases its recovery time. Preliminary results demonstrate that the sensor could also be used to sense vapors of common solvents.

This work presents the structural characterisation of PbS nanofilms deposited by the chemical bath deposition technique at 70±2 °C using Polyethyleneimine, Triethanolamine and Ammonium nitrate as complexing agents, which allow a controlled and constant ion by ion reaction in aqueous medium whose chemical bath reactions take place in basic solutions with typical pH values 9–12, distinguishing the complexes obtained by their thermodynamic stability and kinetic stability. The PbS fundamental stretching frequencies were determined by Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy gives the relative atomic composition and identification of the most intense photoelectron transitions S2p (164 eV) and Pb4f 7/2 (137.34 eV) for the PbS-Nitrate film, which are associated with the Pb (II) oxidation state. The shift to higher binding energies, Pb4f7/2 (139.01 eV) for PbS-Polyethyleneimine and PbS-Triethanolamine show the presence of PbO2 with oxidation state Pb (IV). X-ray diffraction analysis and Raman spectroscopy reveal that PbS deposited nanofilms had pure cubic galena crystalline phase when ammonium nitrate was used as complexing agent, with the Polyethyleneimine complexing agent, the formation of cubic PbS in cubic phase with monoclinic Lanarkite Pb2(SO4)2 traces were observed. Finally, using Triethanolamine as complexing agent, cubic phase PbS with orthorhombic Anglesite and lead oxide (x∼1.57) traces were found. The surface morphology of the samples was obtained by High Resolution Transmission Electron Microscopy. The thin films show three direct band gaps, around 0.77–0.78 and 0.84–0.88 eV belonged to the mid-trap state caused by –Pb dangling bond and S+2 levels and the band gap energy at 0.91–1.10 eV was attributed to the quantum confinement associated to grain size, which were obtained by transmittance.

A fiber optic sensor coated with a thin film of zinc oxide nanorods has been developed to detect methanol in adulterated tequila. Zinc oxide was synthesized by ultrasonic method and was used as vapor sensing media. The measured intensities of transmitted light in the optical sensor were analyzed at different concentrations of methanol in tequila. The sensor presented good response to tequila-methanol mixtures and the observed differences in response and recovery times allowed and easy and economic detection of methanol in commercial tequila. The developed sensor is a simple and economic device to detect methanol in commercial tequilas or another beverage. Moreover, it can be used as a quality control technique in laboratories to distinguish the adulteration and/or contamination degree with methanol.

Sm3+/Eu3+ single doped and co-doped zinc-germanate-tellurite glasses were prepared by the glass melting method. Raman and optical spectroscopic properties of Sm3+, Eu3+ and Sm3+/Eu3+ doped TeO2-GeO2-ZnO glasses have been characterized through optical absorption and pulsed/steady fluorescence. Excitation and emission spectra measurements indicated that the energy transfer process Sm → Eu is active in the samples. The concentration of europium ions was varied to provide red emission for possible control over the chromaticity tuning in the red-orange region. Upon 344 nm excitation, the color of the global emission can be adjusted from orange of 2038 K to reddish-orange of 1683 K by increasing the Eu3+ content from 1 up to 2% mol, and co-doped with 0.5% mol Sm3+. Reddish-orange color purity very close to 100% is attained when the phosphors are excited at 406 nm. The time shortening of Sm3+ emission decay in the presence of Eu3+ was attributed to a Sm3+ → Eu3+ non-radiative energy transfer process. From fitting the Sm3+ emission decay profile with the Inokuti-Hirayama model, it was inferred that the energy transfer process could be dominated by an electric dipole-dipole interaction.