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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.

Here, we report the characterization of one-pot synthesized silicon quantum dots and its employment as luminophore of luminescent solar concentrators (SiQDLSC). Colloidal SiQDs shown attractive optical features such as absorption of high energy photons with wavelengths below 450 nm and a broad band of luminescence with maximum intensity at ∼525nm. The fabricated SiQDLSC shown transmittances of ∼90% over the visible region of the electromagnetic spectrum, while preserving the absorbance characteristics of the colloidal SiQDs. The photoluminescent properties of the SiQDLSC were measured at the edges of the devices, obtaining broad bands of emission with maximum around ∼500 nm. The observed results demonstrate the promising properties of the one-pot synthesized silicon quantum dots and its possible employment as luminophore in building integrated photovoltaic technologies such as SiQDLSC.

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.

There is currently an increased interest in demonstrating white light emitting devices that exhibit a higher energy efficiency compared to the ubiquitous incandescent sources and that are at the same time cost-competitive as well as compatible with a mass-production environment. Under the aforementioned stringent constraints, photoluminescent quantum dots can be considered a suitable option to demonstrate said white light emitting constructs. To this end, the present report discusses the synthesis and characterization of nanoparticles of zinc oxide (ZnO) and zinc sulphide (ZnS) that exhibit Stokes shift effects and optical properties of light absorption in the UV range (~340 nm) and luminescent capabilities obtaining peaks centered in 525 nm and 440 nm, respectively. Colloidal mixtures of these nanostructures were made with different volumetric ratio in order to achieve a near white color emission. Photoluminescence studies of the mixtures were carried out and a chromaticity diagram was made to localize and identify a trend in the luminescent variations of the samples within the International Commission on Illumination (CIE) diagram. The experimental results indicate that quantum dots could be a viable alternative for high-efficiency and cost-competitive white light emitting devices.

Today, finding superior methods for synthesis of graphene oxide (GO) and reduced graphene oxide (rGO) from commercial graphite, is still a challenge. The global industry requires the use of synthesis methods that are price-competitive and also use processes that are environmentally compatible. GO is a substrate used for several chemical transformations, including its reduction to related materials, such as rGO and graphene. The rGO has been used recently to increase catalytic activity in the o-nitroaniline reduction to NaBH4 and Raman activity in test molecules as p-aminothiophenol [1]. Other authors showed that the rGO in combination with carbon nanotubes has the properties of supercapacitors [2]. Mao et al. [3] obtained a gas sensor type field defect transistor of high sensitivity at low concentrations, using sheets of rGO. On the other hand, rGO linked with Cu2O nanocrystals is capable of removing dye pollution from wastewater [4].

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.

Noble metal nanoparticles have received much attention due to their interesting properties that make them useful in different technical fields. Metallic nanoparticles with optical properties in the near infrared region of the electromagnetic spectrum are of great importance for biological applications, in particular photothermal therapy, as it is greatly enhanced by metallic nanoparticles. However, despite the large amount of work that has been done with metallic nanoparticles for thermal therapy, there is a reduced amount of scientific reports about the photothermal stability of most studied nanoparticles. In this work, hollow Au–Ag bimetallic nanoparticles were synthesized via galvanic replacement reaction, with optical properties that can be tuned systematically along the visible and near infrared region of the spectrum, by changing the pH before the synthesis of the templates and by controlling the amount of gold added for the synthesis of the nanoshells. The synthesized nanoparticles exhibit good photothermal properties when illuminated with an 808 nm laser light. An increase of temperature of nearly 20 °C is achieved after 15 minutes of irradiation. Moreover, the Au–Ag nanoparticles show good reusability even after ten heating/cooling cycles. The nanoparticles also retain their optical properties after 12 hours of continuous irradiation and are able to maintain their photothermal characteristics of increasing the temperature at the same levels during the entire process.