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Electrochemical impedance spectroscopy was used to analyze 10 µm thickness TiO2 films containing 250 nm TiO2 nanoparticles (NPs) with anatase crystalline phase deposited on FTO substrates. The TiO2 films were sensitized with CdSe quantum dots (QDs) (4.5 nm) and decorated with Au nanoparticles (NPs) (7 nm) and poly-3-octylthiophene (P3OT) in three different configurations, namely TiO2/QDs, TiO2/Au/QDs, and TiO2/Au/QDs/P3OT. The characteristic absorption bands for each component, TiO2. P3OT, CdSe QDs, and Au NPs, are centered at 338 nm (3.67 eV), 459 nm (2.7 eV), 552 nm (2.24eV), and 517 nm (2.40 eV), respectively. The UV-Vis spectrum of the composite film TiO2/Au/QDs/P3OT shows clear absorption peaks from 338 to 700 nm. Equivalent circuits were proposed for the different configuration interfaces to fit experimental impedances. The results suggest that the introduction of Au NPs into the TiO2/Au/QDs films strongly reduces resistance to the electron flux from QDs to TiO2 and increases the overall charge transport. Meanwhile, P3OT in the TiO2/Au/QD/P3OT films promotes hole transport and increases the capacitance with the electrolyte, reducing the electron leakage and improving the fill-factor and the final light energy conversion efficiency. [ABSTRACT FROM AUTHOR] more...

The synthesis, structural and optical characterization, and application of superparamagnetic and water-dispersed Fe3O4-Au core-shell nanoparticles for surface enhanced Raman scattering (SERS) is reported. The structure of the nanoparticles was determined by scanning transmission electron microscopy (STEM) and high-resolution transmission electron microscopy (HRTEM). STEM images of the Fe3O4-Au core-shell nanoparticles reveal an average diameter of 120 nm and a high degree of surface roughness. The nanoparticles, which display superparamagnetic properties due to the core Fe3O4 material, exhibit a visible surface plasmon resonance (SPR) peaked at 580 nm due to the outer gold shell. The nanoparticles are used as a substrate for surface enhanced Raman scattering (SERS) with rhodamine 6G (R6G) as a Raman reporter molecule. The SERS enhancement factor is estimated to be on the order of 106, which is ∼ 2 times larger than that of conventional gold nanoparticles (AuNPs) under similar conditions. Significantly, magnetically-induced aggregation of the Fe3O4-Au core-shell nanoparticles substantially enhanced SERS activity compared to non-magnetically-aggregated Fe3O4-Au nanoparticles. This is attributed to both increased scattering from the aggregates as well as 'hot spots' due to more junction sites in the magnetically-induced aggregates. The magnetic properties of the Fe3O4 core, coupled with the optical properties of the Au shell, make the Fe3O4-Au nanoparticles unique for various potential applications including biological sensing and therapy. [ABSTRACT FROM AUTHOR] more...

The double-perovskite material Cs 2 TiBr 6 shows excellent photovoltaic potential, making it a promising alternative to lead-based materials. However, its high susceptibility to degradation in air has raised concerns about its practical application. This study introduces an interesting synthesis approach that significantly enhances the stability of Cs 2 TiBr 6 powder. We implemented a gradual cation exchange process by substituting Ti 4+ with Sn 4+ in the efficient microwave-assisted synthesis method, developing a double perovskite Cs 2 Sn x Ti 1-x Br 6 type. A systematic study of increasing concentration of Sn 4+ in Cs 2 TiBr 6 perovskite has been performed to analyze the effect of Sn-doping degree on the chemical and thermal stability of the material and the optical features in both nitrogen and ambient atmospheres, significantly increasing the stability of the material in the air for over a week. Furthermore, introducing Sn 4+ results in a more uniform polygonal crystal morphology of the powders and a slight band gap broadening. We show that microwave-assisted synthesis is highly efficient and cost-effective in producing more sustainable lead-free perovskite materials with enhanced stability and desirable electrical characteristics. This work suggests a promising method for synthesizing perovskite materials, opening new routes for scientific research and applications., (© 2024 The Author(s). ChemSusChem published by Wiley-VCH GmbH.) more...

Theoretical studies have identified cesium titanium bromide (Cs 2 TiBr 6 ), a vacancy-ordered double perovskite, as a promising lead-free and earth-abundant candidate to replace Pb-based perovskites in photovoltaics. Our research is focused on overcoming the limitations associated with the current Cs 2 TiBr 6 syntheses, which often involve high-vacuum and high-temperature evaporation techniques, high-energy milling, or intricate multistep solution processes conducted under an inert atmosphere, constraints that hinder industrial scalability. This study presents a straightforward, low-energy, and scalable solution procedure using microwave radiation to induce the formation of highly crystalline Cs 2 TiBr 6 in a polar solvent. This methodology, where the choice of the solvent plays a crucial role, not only reduces the energy costs associated with perovskite production but also imparts exceptional stability to the resulting solid, in comparison with previous reports. This is a critical prerequisite for any technological advancement. The low-defective material demonstrates unprecedented structural stability under various stimuli such as moisture, oxygen, elevated temperatures (over 130 °C), and continuous exposure to white light illumination. In summary, our study represents an important step forward in the efficient and cost-effective synthesis of Cs 2 TiBr 6 , offering a compelling solution for the development of eco-friendly, earth-abundant Pb-free perovskite materials., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.) more...

Phosphors composed of Gd 1-x RE x AlO 3 (0≤x ≤ 5 RE = Dy or Pr) stoichiometries were synthesized using the reverse coprecipitation pathway. The thermoluminescent responses of all phosphors were studied under beta radiation exposure. Doping the gadolinium aluminate host improved the thermoluminescent response of the phosphors, with the phosphors composed of Gd 0.99 Dy 0.01 AlO 3 and Gd 0.95 Pr 0.05 AlO 3 being the most sensitive. The Dy 3+ ions produced a higher improvement of the thermoluminescent signal than the Pr 3+ ions. Additionally, a proportional relationship between the similarity of the atomic numbers of the dopant and replaced ions and the sensitivity to thermoluminescence was confirmed. Besides, a slight shift of the thermoluminescent peaks toward lower temperatures was detected for doped phosphors. In the repeatability tests applied to the phosphor composed of Gd 0.99 Dy 0.01 AlO 3 , an anomalous increase in sensitization was observed. The observed sensitization was associated with the formation of electron trap clusters resulting from the continuous exposure to beta radiation. Furthermore, another sensitization phenomenon was detected in the phosphor with Gd 0.95 Pr 0.05 AlO 3 stoichiometry when it was heated at low temperatures. The aforementioned striking behavior was related to quasi-continuous distributions of electron traps and the tunneling effect. In regard to linearity, the phosphor composed of Gd 0.99 Dy 0.01 AlO 3 exhibited a linear response with the dose across the entire range of beta doses. However, the response of the Gd 0.95 Pr 0.05 AlO 3 phosphor lost linearity beyond 26.4 Gy of beta dose. The results obtained through the use of the T max -T stop method and deconvolutions suggested an enhancement in the efficiency of the thermoluminescent mechanisms due to the incorporation of activators., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Juan Zarate Medina reports financial support was provided by National Council on Science and Technology (CONACYT-MEXICO)., (Copyright © 2023 Elsevier Ltd. All rights reserved.) more...

The suitable choice of an activator and host combination is essential for synthesizing very sensitive thermoluminescence phosphors. In addition, conspicuous synthesis variables must be optimized to achieve the maximal response. The research presented herein shows that the most recommendable conditions to improve the thermoluminescence response of beta irradiated Gd 1-x Eu x AlO 3 phosphors were: x = 0.02 for europium stoichiometry and 1500 °C for the calcination temperature. The glow curve recorded for the most sensitive phosphor was partially erased by photo-bleaching, and thus, should yield optically stimulated luminescence., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Juan Zarate Medina reports was provided by National Council for Science and Technology. Juan Zarate Medina reports equipment, drugs, or supplies was provided by National Council for Science and Technology., (Copyright © 2022 Elsevier Ltd. All rights reserved.) more...

The relative populations of Cu 38 isomers depend to a great extent on the temperature. Density functional theory and nanothermodynamics can be combined to compute the geometrical optimization of isomers and their spectroscopic properties in an approximate manner. In this article, we investigate entropy-driven isomer distributions of Cu 38 clusters and the effect of temperature on their IR spectra. An extensive, systematic global search is performed on the potential and free energy surfaces of Cu 38 using a two-stage strategy to identify the lowest-energy structure and its low-energy neighbors. The effects of temperature on the populations and IR spectra are considered via Boltzmann factors. The computed IR spectrum of each isomer is multiplied by its corresponding Boltzmann weight at finite temperature. Then, they are summed together to produce a final temperature-dependent, Boltzmann-weighted spectrum. Our results show that the disordered structure dominates at high temperatures and the overall Boltzmann-weighted spectrum is composed of a mixture of spectra from several individual isomers., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Buelna-García, Castillo-Quevedo, Quiroz-Castillo, Paredes-Sotelo, Cortez-Valadez, Martin-del-Campo-Solis, López-Luke, Utrilla-Vázquez, Mendoza-Wilson, Rodríguez-Kessler, Vazquez-Espinal, Pan, de Leon-Flores, Mis-May, Rodríguez-Domínguez, Martínez-Guajardo and Cabellos.) more...

In this work, gold NPs were prepared by the Turkevich method, and their interaction with HPV and cancerous cervical tissues were studied by scanning electron microscopy, energy-dispersive x-ray spectroscopy, confocal and multiphoton microscopy and SERS. The SEM images confirmed the presence and localization of the gold NPs inside of the two kinds of tissues. The light absorption of the gold NPs was at 520 nm. However, it was possible to obtain two-photon imaging (red emission region) of the gold NPs inside of the tissue, exciting the samples at 900 nm, observing the morphology of the tissues. The infrared absorption was probably due to the aggregation of gold NPs inside the tissues. Therefore, through the interaction of gold nanoparticles with the HPV and cancerous cervical tissues, a surface enhanced Raman spectroscopy (SERS) was obtained. As preliminary studies, having an average of 1000 Raman spectra per tissue, SERS signals showed changes between the HPV-infected and the carcinogenic tissues; these spectral signatures occurred mainly in the DNA bands, potentially offering a tool for the rapid screening of cancer. more...