Biopolymers are interesting technological platforms for green and eco‐friendly devices while enabling the desirable biocompatibility. Herein, micro‐ and nanostructures have been fabricated on the biopolymer collagen type I using thermo‐nanoimprinting lithography (T‐NIL) under relatively low temperature and applied pressure. The collagen samples are prepared by spin coating directly on substrates or as self‐standing membranes by casting from cosmetic‐grade ovine collagen acidic solutions. After NIL parameter optimization, complex microstructures and nanostructures can be realized at temperatures as low as 125 °C under an applied pressure of 50 bar for 300 s. The nanopatterns and eventual collagen macrostructure changes are completely characterized by optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal analysis, and spectroscopy techniques. The broad utility of such nanopatterns as Bragg gratings and plasmonic sensors is discussed.

The doping effect of metallic nanoparticles on the photoluminescence of organic molecular systems is commonly ascribed to surface plasmon energy transfer. Here, the photoluminescence band of a columnar liquid crystal coincides with the surface plasmon resonance of gold nanoparticles, while its absorption band partially superimposes with the plasmon resonance of silver nanoparticles. We find that surface plasmon energy transfer between the nanoparticles and the liquid crystalline matrix is not the only mechanism that explains photoluminescence quenching and enhancement. Temperature and molecular ordering play important roles in this process.

This paper describes the synthesis of new naphthalene diimide (NDI) derivatives obtained in good yields from the reaction between 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) and different p-alkoxy-substituted anilines. The photophysical properties of the NDIs were investigated in solution and the solid state. UV-visible absorption spectra in 1,4-dioxane, dichloromethane, and acetonitrile showed absorption maxima at approximately 375 nm, related to symmetry and spin allowed 1 pi-pi* electronic transitions. These compounds did not exhibit fluorescence emission in the studied solvents. Electrochemical studies have indicated that the presence of different alkyl chains significantly affects the capacity of NDIs when used as organic cathodes in Al-graphite batteries due to variations in their ability to intercalate tetrachloroaluminate. The organic cathodes incorporating NDIs with varying alkyl chain lengths exhibited distinct capacities: 123.5 mA h g-1- 1 for 3a , 101.6 mA h g-1- 1 for 3b , and 157.3 mA h g-1- 1 for 3c , with a capacity retention of approximately 54 % after 15 charge-discharge cycles. These findings highlight the crucial role of alkyl chain modification in optimizing the electrochemical performance of organic cathodes.

Perovskite nanocrystals have excellent optical properties but suffer from environmental instability and production up-scaling which limit their commercial application. Here, we report the gram-scale ultrasound-mediated synthesis of silane passivated CsPbBr3 nanocrystals using (3-aminopropyl) triethoxysilane (APTS) as the primary surface ligand surface. The surface engineering endowed the CsPbBr3@SiOR NCs with extended environmental stability, a narrow emission bandwidth and a high photoluminescence quantum yield (PLQY > 75%). Thanks to these excellent optical properties, high-efficiency lateral and vertical photodetectors were fabricated. In particular, the layered vertical photodiode composed of ITO/Ga2O3/CsPbBr3/Au exhibited a broadband photoresponse from 350-700 nm with a responsivity peaking at 44.5.1 A W-1 and specific detectivity above 10(13) Jones when illuminated at 470 nm wavelength and biased at +5 V. These results correspond to the best-in-class performance perovskite nanocrystal PD and confirm the extraordinary potential of CsPbBr3@SiOR for the development of efficient optoelectronic devices.

Pyrite (FeS2) is one of the main tailings derived from coal mining. When processed, pyrite has several applications with high value-added, in contrast, if improperly discarded, it causes major environmental impacts, like the acid mine drainage. For those reasons, the seeking for beneficiation techniques of Pyrite has been the target of numerous studies. One of the most employed techniques is the separation by density using heavy liquids, like bromoform, as a separation medium. In the present work, we propose the use of lithium heteropolytungstate (LST), a non-halogenated and non-toxic solution, as an alternative in the separation by density method. For the experiments, raw pyrite samples were collected from the tailings of coal extraction from a mining company in Santa Catarina, Brazil. After the separation process, the samples before and after the beneficiation were characterized by XRD, FUR, and XRF techniques. The results revealed that the separation technique used in this work led to a significant increase in the concentration of pyrite, going from less than 10% in the raw sample and reaching almost 80% after processing. This impressive result reveals that LST represents a promising alternative for separating pyrite by density techniques, showing much greater effectiveness than other heavy liquids used in the literature, in addition to being environmentally friendly.

A systematic study of the synthetic procedure to improve quantum efficiency of luminescent hybrid perovskite QDs through ligand-assisted precipitation method is presented. Particularly, the influence of the dielectric constant and dipole moment of the antisolvent on the reaction time and the photophysical properties of the QDs is highlighted. After evaluating the influence of antisolvents and optimizing experimental parameters such as reaction time and Pb excess of the precursor, colloidal crystalline MAPbBr3QDs with exceptionally high absolute quantum yield up to 97.7% in solution and 69.1% in solid film were obtained. Finally, MAPbBr3QDs precipitated from anisole were processed like UV-curable nanocomposite as efficient down conversion layer resulting in very narrow green emission light-emitting diode.

Since 1980's natural polymers are studied as sources for solid polymer electrolytes (SPEs) in optoelectronic equipment because of their abundance in the environment, inexpensiveness, and biological degradation characteristics. Xanthan gum is a naturally occurring polysaccharide found in the microbial world, and its main advantage is to produce transparent solutions with elevated viscosity and stability including wide range of temperature. Therefore, the present paper presents the FTIR and impedance study of xanthan gum as a host matrix for the ionically conducting membranes. Different contents of proton conducting species were incorporated into the polymer host and the membranes were realized by the method of solution casting. The FTIR results indicated that the electrolytes were formed by the polymeric network. The frequency independent conductivity response pointed the best dc conductivity values of 7.26 x 10(-5) to 3.92 x 10(-4) S cm(-1), in the temperature range from 20 to 80 degrees C, for the sample with 2.00 g of acetic acid. The occurrence of the electrode polarization was interpreted by the combination of the complex dielectric permittivity (epsilon*), loss tangent (tan delta), conductivity (sigma), and complex electric modulus (M*). (C) 2019 Elsevier Ltd. All rights reserved.

We report a proof-of-concept micro-spectroscopy, stochastic dynamics, and optical trapping study of a well-known reaction for methylene blue photodegradation catalyzed by titanium dioxide aggregates and nanotubes. Photocatalysis is performed under a high concentration of reactants and catalyst loading to characterize the fundamental chemical kinetics and dynamics aspects of this reaction under in operando conditions. We also report the effect of substrate concentration, light intensity, and substrate/catalyst ratio on the kinetic profiles. Optical imaging is used to quantify how spatial and concentration variations affect the reaction kinetics. To study the dynamics of individual nanoparticle catalysts under in operando conditions, we use optical trapping to characterize the stochastic dynamics of single TiO2 nanotubes. Overall, the results presented here indicate that the setup can be used to monitor photocatalytic degradation of methylene blue with simultaneous measurements of images and spectra while also monitoring the catalyst Brownian motion at the single-particle level.

Hybrid organic-inorganic lead halide perovskite materials show great promise in a number of optoelectronic applications, including solar cells, light emitting diodes, and photodetectors. Understanding their intrinsic material properties is critical to enhancing device performance and enabling innovative material and device designs. Here, we study lattice dynamics using far-infrared (FIR) reflectance and photogenerated carrier dynamics using surface photovoltage (SPV) measurements on high-quality methylammonium lead bromide (MAPbBr3) single crystals. FIR reflectance shows three coherent infrared-active phonon modes between 40 and 200 cm−1 that result in reststrahlen bands with much higher peak reflectance than has been previously reported. The phonon mode strength and damping are comparable to classical oxide perovskite single crystals. However, the effects of defects on photogenerated carrier recombination are still evident in SPV measurements. By performing SPV over different spectral ranges, we are able to separate the effects of surface and bulk defects on the recombination dynamics of photogenerated charge carriers. We further apply SPV measurements to obtain the minority carrier (electron) diffusion length for the MAPbBr3 crystal. This study demonstrates that both FIR reflectance and SPV measurements provide useful information on the electromagnetic response properties of halide perovskite single crystals.

In this work, a solvent-free method to deposit in-situ methylammonium lead bromide (MAPbBr(3)) perovskite thin films is discussed. Spin-coating methods used for hybrid perovskite deposition typically use solvents that might remain in the films after processing, potentially causing accelerated film degradation. Furthermore, spin-coating might not be suitable for applications that require thick films (>500 nm). To address these issues, a close space sublimation process was implemented to deposit solvent-free and in-situ MAPbBr(3) films with variable thicknesses. A post-deposition annealing protocol was developed that results in smooth perovskite films as thick as 3 mu m. Post-deposition anneal also reduces a photoluminescence emission band that originates from surface defects. The resulting films were chemically, optically and structurally studied and hysteresis-free PIN diodes with metal-oxide semiconductors as p and n-type layers were fabricated and analyzed. The results indicate that high quality perovskite films with variable thickness can be obtained by the close space sublimation (CSS) process demonstrated here. Although MAPbBr(3) was selected for this study, this CSS method demonstrated can be easily applied to other hybrid perovskites.

A small cross-section of silver nanoparticles (AgNPs) placed at the rear-part of the solar cell avoids the parasitic absorption of the nanoparticles which is the biggest barrier for plasmonic structures when acting as photocurrent enhancers. Herein, we demonstrate p-i-n planar perovskite solar cells with the structure ITO/PEDOT:PSS/MAPbI3/PCBM/Ni:Au, where the PCBM electron extraction layer (EEL) was intentionally modified with variable amounts of AgNPs. The addition of small amounts of AgNPs (e.g., 5 wt. %) into the PCBM improved the overall reproducibility and reliability of the solar cell fabrication process after optimization. Plasmonic simulations suggest that any plasmonic-optical effects are relatively small compared to sample absorbance due to perovskite alone. It has been concluded that plasmonic-electrical effects play a major role in averaged performance improvement. Therefore, the addition of small AgNPs in low concentration to the EEL layer accounts for higher Jsc, Voc and FF as a result of a better perovskite coverage by the EEL and an improved charge carrier collection as evidenced by morphological and electrical analysis.

The paper presents a systematic study of the electrochromic properties of thin films of V2O5:TiO2 for a possible utilization as counter-electrode in electrochromic devices. The V2O5:TiO2 thin films were prepared by the sol-gel process and deposited on a substrate of fluorine-tin oxide transparent electrode (FTO) using the dip coating technique and heat treatment at 350 degrees C for 30 min. The films were characterized by chronocoulometry, cyclic voltammetry (CV), UV-Vis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), profilometry, and X-ray diffraction (XRD). The best results were obtained for the film of V2O5 with 7.5 mol% of TiO2, which presented highest ion storage capacity of similar to 106 mC cm(-2) and redox reversibility of 1. The diffusion of the Li+ ions into the thin films was modeled by solving Fick equations with appropriate boundary conditions for a plane sheet geometry. Besides that, these films showed optical modulation of 35% at 633 nm after coloration and bleaching. The XRD patterns revealed that the films have an orthorhombic crystal structure; the AFM and the profilometry confirmed roughness and thickness of 16.76 and 617 nm, respectively.

The preparation of bio-organic nanostructures containing dipeptides and conjugated polymers like P3HT–diphenylalanine is trigged by ultrasound energy owing the study of such hybrid materials in solution processed OFETs and beyond.

Neste trabalho, é explorado o uso de uma das proteínas da seda, a Fibroína, como agente dispersante para produção de dispersões estáveis de nanotubos de carbono de parede única (SWCNT).As dispersões

Herein a useful methodology to study optical properties of cholesteric liquid crystals (Ch-LC) is proposed by using the Fourier decomposition ellipsometry technique to calculate the Stokes parameters of transmitted and reflected light in the UV-Vis spectral range. Combining Bragg reflection and optical activity we were able to obtain similar to 100% of linear or circular light polarization from the Ch-LC sample using achromatic and non-polarized light source. The photonic bandgap and the polarization components can be controlled with the temperature as a result of alterations in the helix pitch of the cholesteric phase. Finally, it is demonstrated the correlation between the dissymmetry factor (g) calculated via the Stokes parameter S-3 and the reflection spectrum. The data revealed that the maximum value of S3 is not coincident with the peak of maximum reflection. The reflected or transmitted light analysis via Stokes parameters obtained by ellipsometry showed an alternative and low cost method for optical characterization in Ch-LC. (C) 2015 Elsevier B.V. All rights reserved.

In this contribution we explore the spray deposition technique to achieve smooth films based on the conductive polymer PEDOT:PSS. Two different spray systems were used and compared namely: (a) handheld airbrush and (b) automated ultrasonic spray system. For each system a number of parameters were pre-adjusted during coating control experiments such as spray head distance, angle and cone for airbrush as well as flow rate, power and focus for ultrasonic nozzle. Water-based solutions of PEDOT:PSS having 20% of N-methylpyrrolidone (NMP) were sprayed on glass substrates at temperatures ranging from 75 to 150 °C. The resulting films were further chemically treated with ethylene glycol (EG) and evaluated with respect to their morphological, electrical and optical properties. Before EG-treatment the ultrasonic spraying resulted in smoother films with conductivity up to 2–3.9 times higher than their airbrushed counterparts. Deposition temperature proved to have minor effect on the morphological and electro-optical properties of PEDOT:PSS films. On the other hand, the film conductivity was enhanced, peaking at 610.1 S cm−1 for ultrasonic spraying, when further chemically modified by EG. IR microspectroscopy mapping analysis, Raman spectroscopy and XRD data indicated a phase-separation between PEDOT and PSS chains and increasing crystallinity in the ultrasonically sprayed films. The application of such PEDOT:PSS films as transparent electrode in flexible AC EL devices is demonstrated.

In this contribution, we describe the development of inkjet printable PEDOT:PSS polymer-based inks for fabrication of polymeric organic light-emitting devices (OLEDs). By using a 10×10 array of SU8 wells on ITO/glass substrates, guided deposition of PEDOT in a simulated OLED pixel structure was possible. The quality of the printed patterns was controlled by fine tuning of the surface wetting properties using self-assembled monolayers (SAMs) and/or oxygen reactive plasma. All the investigated surface treatments improved the quality of the printed pattern. However, the O2 plasma treated surfaces, which had the highest free energy, resulted in smoother and more uniform PEDOT films than did the SAM-coated surfaces. Rainbow-like features and non-uniformities observed at the edges of the film were attributed mostly to the well-known coffee stain effect and the drying environment. A good reduction of such features was achieved by decreasing the PEDOT content in the inks.

Experiments on mixtures of different nematic-liquid-crystal hosts with a chiral dopant to induce the appearance of blue phases (BPs) is reported. The phase behavior and transition temperatures of the mixtures were studied by temperature-dependent polarized optical microscopy, variable temperature X-ray diffraction, and reflectance measurements. After completely characterized, a selected LC mixture presenting BPs was submitted to polymer-stabilization using UV-curable monomers. By using a specific combination of a pro-mesogenic (B11) and a branched-chain acrylate (EHA) monomer, a uniform porous microstructure is formed providing a stable BP.