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Plasmonic photothermal therapy (PPTT), as an increasingly studied treatment alternative, has been widely regarded mostly as a surface tissue treatment choice. Although some techniques have been implemented for interstitial tumors, these involve some grade of invasiveness, as the outer skin is usually broken to introduce light-delivering optical fibers or even catheters. In this work, we present a potential non-invasive strategy using the stereotactic approach, long employed in radiosurgery, by converging multiple near infrared laser beams for PPTT in tissue-equivalent optical phantoms that enclose small gel spheres and simulate interstitial tissue impregnated with plasmonic nanoparticles. The real-time in-depth monitoring of temperature increase is realized by an infrared camera face-on mounted over the phantom. Our results show that a significant reduction in the surface heating can be achieved with this configuration while remarkably increasing the interstitial reach of PPTT, assuring a ∼ 6 ∘ C temperature increase for the simulated tumors at 10 mm depth and ∼ 4 ∘ C at 15 mm depth and opening up new possibilities for future clinical applications.

The chemical properties of engine oil are part of the main parameters to evaluate its condition since oxidation starts chemical reactions that alter its operating conditions. In this work, the chemical properties of engine oil were analyzed based on the standard ASTM E2412 by FT-IR spectroscopy to evaluate the lubricating oil condition. Furthermore, a sensor based on the position of the localized surface plasmon resonance (LSPR) band of silver nanoparticles (AgNP), synthesized by the laser-assisted photoreduction method, was developed. This plasmonic sensor can detect changes in the permittivity of the oil, caused by the modification of the chemical properties of the lubricant. The response of the sensor during the study of degraded oil resulted in a notorious displacement to higher wavelengths of the LSPR band as mileage increases. The results of FT-IR analysis were correlated with the measurements of the proposed sensor presenting linear trends with good correlation (R2 &gt, 0.9491).

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.

We present a new method to calculate the complex refractive index of spherical scatterers in a novel optical phantom developed by using homemade monodisperse silica nanospheres embedded into a polyester resin matrix and an ethanol–water mixture for applications in diffuse imaging. The spherical geometry of these nanoparticles makes them suitable for direct comparison between the values of the absorption and reduced scattering coefficients ( μ a and μ s ′ , respectively) obtained by the diffusion approximation solution to the transport equation from scattering measurements and those obtained by the Mie solution to Maxwell’s equations. The values of the optical properties can be obtained by measuring, using an ultrafast detector, the time-resolved intensity distribution profiles of diffuse light transmitted through a thick slab of the silica nanosphere phantom, and by fitting them to the time-dependent diffusion approximation solution to the transport equation. These values can also be obtained by Mie solutions for spherical particles when their physical properties and size are known. By using scanning electron microscopy, we measured the size of these nanospheres, and the numerical results of μ a and μ s ′ can then be inferred by calculating the absorption and scattering efficiencies. Then we propose a numerical interval for the imaginary part of the complex refractive index of S i O 2 nanospheres, n s , which is estimated by fixing the fitted values of μ a and μ s ′ , using the known value of the real part of n s , and finding the corresponding value of I m ( n s ) that matches the optical parameters obtained by both methods finding values close to those reported for silica glass. This opens the possibility of producing optical phantoms with scattering and absorption properties that can be predicted and designed from precise knowledge of the physical characteristics of their constituents from a microscopic point of view.

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.

In this work, a capacitive sensor made of recycled material is proposed to monitor oil quality in automotive workshops in order to reduce the waste of useful lubricant oil caused by shorter periods of use than those established by the manufacturers. The sensor was fabricated from a recycled aluminum heat sink and used to measure the permittivity of oil samples. The proposed method was compared with Fourier-transform infrared spectroscopy analysis to evaluate degradation parameters, as described in standard practice ASTM E-2412. The obtained results showed good agreement between both techniques, validating the use of the proposed sensor to evaluate oil condition. The use of permittivity measurements could be used to evaluate oil quality in an easier, faster, and economical way compared with other laboratory tests.

Efficient heat generation by plasmon-resonant gold nanoparticles, together with their biocompatibility and high specificity of biomolecular recognition, opens new possibilities for applications in biomedical applications. In this work, we present an improved method of monitoring surface temperature changes subjected to external stimulation by dynamic IR thermography. The method is based on the careful analysis of an IR image sequence recorded before, during, and after the stimulation that allows one to select areas with significant temperature variation and evaluate temporal behavior of the surface temperature. The method was applied for the experimental study on the photothermal effect in a gold hydrosol containing hollow gold nanoparticles heated with laser beam. Under these conditions, it was seen that the surface temperature of the gold hydrosol (measured with a FLIR SC655 InfraRed Camera, resolution 640 × 480 pixels) under the laser beam gradually increases and reaches a saturation level. It was shown that the developed method is capable of producing a quantitative analysis of the changes in the surface temperature distribution of the gold hydrosol, as well as characterizing the photothermal properties of the nanoparticles.

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.

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].

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.

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.

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.

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.

Recently, the paraelectric response of water was investigated in the range 0–100 °C. It showed an almost perfect Curie–Weiss behaviour up to 60 °C, but a slight change in slope of 1/ed versus T at 60 °C was overlooked. In this work, we report optical extinction measurements on metallic (gold and silver) nanoparticles dispersed in water, annealed at various temperatures in the range from 20 to 90 °C. An anomalous response at 60 °C is clearly detectable, which we associate to a subtle structural transformation in the water molecules at that temperature. This water anomaly is also manifested by means of a blue shift in the longitudinal surface plasmon resonance of the metallic nanoparticles for the solutions annealed at temperatures higher than about 60 °C. A reanalysis of 1/ed (T) for water in the whole temperature range leads us to conclude that the water molecule undergoes a subtle transformation from a low temperature (0–60 °C) configuration with a dipole moment μ1 = 2.18 D (close to the molecular dipole...

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.

Silver nanoparticles were synthesized in aqueous solution using an ecofriendly, fast, and easy photochemical technique through the use of Albizia lebbeck (L.) Benth seed (ALS) extract and sunlight. The phytochemical screening of ALS extract revealed the presence of reducing carbohydrates, and saponins. Also, infrared spectroscopy analysis of the ALS extract confirms the presence of functional groups, characteristics of these compounds. The experiments were conducted near noon during winter by exposing aqueous mixtures of silver nitrate and ALS extract to sunlight at 25 °C. The nanoparticles were characterized by optical absorption spectroscopy, Fourier-transform infrared spectroscopy, and scanning transmission electron microscopy. The nanoparticle formation was evaluated by following the temporal evolution of the absorbance. This data was analyzed using first-order kinetics, finding good correlation to the experimental data. The nanoparticle micrograph analysis shows narrow size distribution and acceptable polydispersity indices. The sunlight driven synthesis of silver nanoparticles using ALS extract is more effective to produce small spheroidal AgNPs than sodium citrate. In addition, ALS extract inhibits the growth of nanoparticles with different morphologies, even when both reducing agents are incorporated at the same time. The proposed methodology presents a reliable and sustainable way to obtain small-sized silver nanoparticles according to the principles of green chemistry.

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.

National Council of Science and Technology (CONACyT) [INFR-226208-2014, INFR-255791-2015]; CONACYT

Silver nanoparticles were synthesized by direct exposure of mixtures of silver nitrate and sodium citrate to sunlight. The reactions were performed near noon, at ~32 °C during winter, varying the precursors ratio. Nanoparticles were characterized by optical absorption spectroscopy, scanning transmission electron microscopy, as well as proton nuclear magnetic resonance spectroscopy. The kinetic of nanoparticles formation was followed by the temporal evolution of absorbance, and analyzed by using Finke-Watzky two-step model, showing good fit to experimental data. A possible reaction mechanism for the formation of silver nanoparticles is proposed based in the experimental results and the kinetic analysis. This mechanism consists of multiple stages, where the formation of complexes between citrate and cationic silver dimers limits the nucleation process and determines the final size and morphology of the nanoparticles. The proposed approach offers a simple, economic and ecological route for the synthesis of silver nanoparticles.

2,4-Dinitrodiphenylamine (I) , 2-nitro-4-(trifluoromethyl)aniline (II) and 4-bromo-2-nitroaniline (III) have been investigated by DFT and experimental FTIR, Raman and UV–Vis spectroscopies. The gas-phase molecular geometries were consistent with similar compounds already reported in the literature. From the vibrational analysis, the main functional groups were identified and their absorption bands were assigned. Some differences were found between the calculated and the experimental UV–Vis spectra. These differences were analyzed and explained in terms of the TD-DFT/B3LYP limitations, which were mainly attributed to charge-transfer (CT) effects. These findings were in agreement with previous works, which reported that TD-DFT/B3LYP calculations diverge from experimental results when the electronic transitions involve CT. Despite this, TD-DFT/B3LYP calculations provided satisfactory results and a detailed description of the electronic transitions involved in the absorption bands of the UV–Vis spectra. In terms of the NLO properties, it was found that compound (I) is a good candidate for NLO applications and deserves further study due to its good β values. However, the β values for compounds (II) and (III) were negatively affected compared to those found on o- nitroaniline.