Search Results (115)

We investigated a novel natural dye-sensitized solar cell (DSSC) utilizing gadolinium ruthenate pyrochlore oxide Gd₂Ru₂O₇ (GRO) as a photoanode and compared its performance to the TiO₂-Gd₂Ru₂O₇ (TGRO) combined-layer configuration. The films were fabricated using the spin-coating technique, resulting in spherical grains with an estimated mean diameter of 0.2 µm, as observed via scanning electron microscopy (SEM). This innovative photoactive gadolinium ruthenate pyrochlore oxide demonstrated strong absorption in the visible range and excellent dye adhesion after just one hour of exposure to natural dye. X-ray diffraction confirmed the presence of the pyrochlore phase, where Raman spectroscopy identified various vibration modes characteristic of the pyrochlore structure. Incorporating Gd₂Ru₂O₇ as the photoanode significantly enhanced the overall efficiency of the DSSCs. The device configuration FTO/compact-layer/Gd₂Ru₂O₇/Hibiscus-sabdariffa/electrolyte(I⁻/I₃⁻)/Pt achieved a high efficiency of 9.65%, an open-circuit voltage (Voc) of approximately 3.82 V, and a current density of 4.35 mA/cm² for an active surface area of 0.38 cm². A mesoporous TiO₂-based DSSC was fabricated under the same conditions for comparison. Using impedance spectroscopy and cyclic voltammetry measurements, we provided evidence of the mechanism of conductivity and the charge carrier’s contribution or defect contributions in the DSSC cells to explain the obtained Voc value. Through cyclic voltammetry measurements, we highlight the redox activities of hibiscus dye and electrolyte (I⁻/I₃⁻), which confirmed electrochemical processes in addition to a photovoltaic response. The high and unusual obtained Voc value was also attributed to the presence in the photoanode of active dipoles, the layer thickness, dye concentration, and the nature of the electrolyte. Full article

The development of ultraflexible and sensitive gas sensors is critical for advancing next-generation environmental monitoring and healthcare diagnostics. In this work, we demonstrate an ultraflexible chemiresistive nitrogen dioxide (NO₂) sensor integrated with a photopatterned porous poly(3-hexylthiophene) (P3HT)/SU-8 blend film as an active sensing layer. The porous microarchitecture was fabricated via high-resolution photolithography, utilizing SU-8 as a photoactive porogen to template a uniform, interconnected pore network within the P3HT matrix. The engineered porosity level ranged from 0% to 36%, substantially improving gas diffusion kinetics to enlarge the accessible surface area for analyte adsorption. Our sensor exhibited a marked enhancement in sensitivity at an optimized porosity of 36%, with the current response at 30 ppm NO₂ increasing from 354% to 3201%, along with a detection limit of 0.7 ppb. The device further exhibited a high selectivity against common interfering gases, including NH₃, H₂S, and SO₂. Moreover, the porous structure imparted excellent mechanical durability, maintaining over 90% of its initial sensing performance after 500 bending cycles at a 1 mm radius, underscoring its potential for integration into next-generation wearable environmental monitoring platforms. Full article

Hydrogen-bonded cross-linked main chain azobenzene (azo) photoactive polymers have broad application prospects in flexible actuators, optical actuators, and other fields. Most of the research on this kind of photoresponsive material is mainly focused on air, and exploration in solvents remains underexplored. In this paper, azobenzene polyamide ester semicrystalline polymer (PEA-6T) with hydrogen-bond cross-linking was synthesized by Michael addition polymerization. The uniaxially oriented polymer film with high orientation (48.85%) and fast response (5 s under UV light and 55 s under visible light) was obtained by a simple solution casting/mechanical stretching method. Compared with PEA-2T and PEA-4T, PEA-6T exhibits enhanced mechanical properties (elastic modulus increased by 17.4%; yield strength increased by 34.1%; breaking strength increased by 75.4%; elongation at break increased by 33.8%; toughness increased by 101.3%; photoinduced stress increased by 43.5%) and reduced light response time (decreased by 58.3% in ultraviolet light and 50% in visible light) due to the elongation of the compliant chain length. The thin PEA-6T film exhibited light-induced deformation not only in air but also in polar solvents such as water, methanol, ethanol, butanol, and saline solutions (e.g., normal saline, 0.9 wt% NaCl, and simulated seawater, 3.5 wt% NaCl). In addition, polarizing optical microscope (POM) observations showed that the brightness and texture direction of the films remained stable (Δ_Brightness < 5%), the light response time was consistent (6 s under UV light, 65 s under visible light), the light-induced stress retention rate was 95%, and the films exhibited good solvent resistance. This study bridges the research gap in azobenzene photoresponsive materials in solvent environments, and the material shows potential for applications in marine equipment coatings or biomedical actuators. Full article

The photosensitive properties of smart photoactive polymers give them a wide range of potential applications across various fields. This study focuses on designing polymeric systems that incorporate hydrophilic polymers, with the primary goal of adapting these materials for biological applications. Specifically, it aims to contribute to the development of photochromic materials for optical processing, utilizing both molecular and macromolecular components. Additionally, this study evaluates the effectiveness of photoactive polymers in photodynamic therapy (PDT). It details the synthesis and characterization of photoactive copolymers derived from maleic anhydride (MAn) combined with vinyl monomers such as 2-methyl-2-butene (MB) and 1-octadecene (OD), as well as the organic compound 1-(2-hydroxyethyl)-3,3-dimethylindoline-6-nitrobenzopyran (SP). The two novel optically active alternating polymeric systems, poly(maleic anhydride-alt-octadecene) and poly(maleic anhydride-alt-2-methyl-2-butene), were functionalized with SP through an esterification process in a 1:1 monomer feed ratio, using pyridine as a catalyst. This methodology incorporated approximately 100% of the photoactive molecules into the main acrylic chain to prepare the alternating copolymers. These copolymers were characterized by UV-visible, FTIR, and 1H-NMR spectroscopy and analysis of their optical and thermal properties. When exposed to UV light, the photoactive polymer films can develop a deep blue color (566 nm in the absorption spectra). Finally, the study also assesses their capacity for photodynamic antimicrobial action in organic film. Notably, the photoactive P(MAn-alt-2MB)-PS significantly enhances the photodynamic antimicrobial activity of the photosensitizer Ru(bpy) against two bacterial strains of Staphylococcus aureus, reducing the minimum inhibitory concentration (MIC) from 2 µg/mL to 0.5 µg/mL. Therefore, 4 times less photosensitizer is required when mixed with the photoactive polymer to inhibit the growth of antibiotic-sensitive and -resistant bacteria. Full article

We report the photocatalytic (PC) response of titanium oxide (TiO_x) films grown by reactive DC magnetron sputtering under oblique-angle-deposition (OAD) and subjected to post-deposition flash-lamp-annealing (FLA). Under ballistic growth conditions, OAD yields TiO_x films with either compact or inclined columnar structure as the deposition incidence angle (α) with respect to the substrate normal varies from zero to grazing. On the one hand, films produced for α ≤ 45° display a compact and opaque structure comprising the formation of nanocrystalline cubic titanium monoxide (c-TiO) phase. On the other hand, films grown at larger α (≥60°) display tilted columns with amorphous structure, yielding highly porous films and an increased transparency for α > 75°. For TiO_x films grown at large α, FLA induces phase transformation to nanocrystalline anatase from the amorphous state. In contrast to as-grown samples, FLA samples display PC activity as assessed by bleaching of methyl orange dye. The best PC performance is attained for an intermediate situation (α = 60–75°) between compact and columnar structures. The obtained photoactivity is discussed in terms of the different microstructures obtained by OAD and posterior phase formation upon FLA. Full article

Bulk heterojunction (BHJ) organic solar cells (OSCs) represent a promising technology due to their cost-effectiveness, lightweight design and potential for flexible manufacturing. However, achieving a high power conversion efficiency (PCE) and long-term stability necessitates optimizing the interfacial layers. Zinc oxide (ZnO), commonly used as an electron extraction layer (EEL) in inverted OSCs, suffers from surface defects that hinder device performance. Furthermore, the active control of its optoelectronic properties is highly desirable as the interfacial electron transport and extraction, exciton dissociation and non-radiative recombination are crucial for optimum solar cell operation. In this regard, this study investigates the sulfur doping of ZnO as a facile method to effectively increase ZnO conductivity, improve the interfacial electron transfer and, overall, enhance solar cell performance. ZnO films were sulfur-treated under various annealing temperatures, with the optimal condition found at 250 °C. Devices incorporating sulfur-doped ZnO (S-ZnO) exhibited a significant PCE improvement from 2.11% for the device with the pristine ZnO to 3.14% for the OSC based on the S-ZnO annealed at 250 °C, attributed to an enhanced short-circuit current density (J_sc) and fill factor (FF). Optical and structural analyses revealed that the sulfur treatment led to a small enhancement of the ZnO film crystallite size and an increased n-type transport capability. Additionally, the sulfurization of ZnO enhanced its electron extraction efficiency, exciton dissociation at the ZnO/photoactive layer interface and exciton/charge generation rate without altering the film morphology. These findings highlight the potential of sulfur doping as an easily implemented, straightforward approach to improving the performance of inverted OSCs. Full article

Enhancing the performance of organic solar cells (OSCs) is essential for achieving sustainability in energy production. This study presents an innovative strategy that involves fine-tuning the thickness of the bulk heterojunction (BHJ) photoactive layer at the nanoscale to improve efficiency. The organic blend D18:L8-BO is utilized to capture a wide range of photons while addressing the challenge of minimizing optical losses from low-energy photons. The research incorporates SnO₂ and ZnO as electron transport layers (ETLs), with PMMA functioning as a hole transport layer (HTL). A comprehensive analysis of photon absorption, charge carrier generation, localized energy fluctuations, and thermal stability reveals their critical role in enhancing the efficiency of D18:L8-BO active films. Notably, introducing SnO₂ as an ETL significantly decreased losses and modified localized energy, achieving an impressive efficiency of 19.85% at an optimized blend thickness of 50 nm with low voltage loss (ΔV_oc) of 0.4 V within a J_sc of 28 mA cm⁻² by performing an optoelectronic simulation employing “Oghma-Nano 8.1.015” software. In addition, the SnO₂-based structure conserved 88% of the PCE at 350 K compared to room temperature PCE, which describes the high thermal stability of this structure. These results demonstrate the potential of this methodology in improving the performance of OSCs. Full article

This work explores the deposition of hexagonal (h-) LuMnO₃ thin films in the P6₃cm phase and investigates the conditions under which the synergy of ferroelectric and photoactive properties, can be achieved to confirm the potential of this material for applications in the development of next-generation photovoltaic devices. Single-phase h-LuMnO₃ was successfully deposited on different substrates, and the thermal stability of the material was confirmed by Micro-Raman spectroscopy analysis from 77 to 850 K, revealing the suitable ferro- to para-electric transition near 760 K. Optical measurements confirm the relatively narrow band gap at 1.5 eV, which corresponds to the h-LuMnO₃ system. The presence of domain structures and the signature of hysteresis loops consistent with ferroelectric behaviour were confirmed by piezoresponse force microscopy. In addition, light-dependent photocurrent measurements revealed the photoactive sensitivity of the material. Full article

The fabrication of metal oxide semiconductor heterostructures is a major way to enhance their properties in photocatalytic and antibacterial applications. In the present work, ZnO/α-Fe₂O₃, In₂O₃/α-Fe₂O₃, and SnO₂/α-Fe₂O₃ are chosen to create the heterostructure of thin films using the spray pyrolysis method. This paper compares the experimental results of the structural and morphological properties of the prepared thin layers using XRD, Raman and SEM. The X-ray diffraction shows that the obtained thin film heterostructures crystallize in a hexagonal phase of ZnO, a cubic phase of In₂O₃ and a tetragonal structure of SnO₂, with all of the preceding phases positioned on the rhombohedral phase of the hematite α-Fe₂O₃. In addition, the SEM study provided the morphology and surface structure and confirmed the presence of a highly folded, rough, uneven surface with imperfections of 20 and 65 nm for In₂O₃/α-Fe₂O₃ and SnO₂/α-Fe₂O₃. The photoactivity of the prepared materials was tested via the photocatalytic degradation of methylene blue (MB) dye. Consequently, our findings demonstrate that the cracked surface improves the rapid absorption of contaminants and allows water to easily pass through the surface of the thin layers. Finally, the antibacterial abilities of ZnO/α-Fe₂O₃, In₂O₃/α-Fe₂O₃, and SnO₂/α-Fe₂O₃ thin films were investigated by using the agar well-diffusion technique, comparing the results to the Gram-negative of Pseudomonas aeruginosa and Gram-positive of Bacillus subtilis, and these thin films were found to have high antibacterial activity. Full article

Photoelectrochemically active WO₃ films were fabricated by electrodeposition from an acidic (pH 2), hydrogen-peroxide-containing electrolyte at −0.5 V vs. SCE. WO₃-TiO₂ composites were then synthesized under the same conditions, but with 0.2 g/L of anatase TiO₂ nanoparticles (⌀ 36 nm), mechanically suspended in the solution by stirring. After synthesis, the films were annealed at 400 °C. Structural characterization by XRD showed that the WO₃ films exhibit the crystalline structure of a non-stoichiometric hydrate, whereas, in WO₃-TiO₂, the WO₃ phase was monoclinic. The oxidation of tungsten, as revealed by XPS, was W⁶⁺ for both materials. Ti was found to exist mainly as Ti⁴⁺ in the composite, with a weak Ti³⁺ signal. The efficiency of the WO₃ films and composites as an oxygen evolution reaction (OER) photo-electrocatalyst was examined. The composite would generate approximately three times larger steady-state photocurrents at 1.2 V vs. SCE in a neutral 0.5 M Na₂SO₄ electrolyte compared to WO₃ alone. The surface recombination of photogenerated electron–hole pairs was characterized by intensity-modulated photocurrent spectroscopy (IMPS). Photogenerated charge transfer efficiencies were calculated from the spectra, and at 1.2 V vs. SCE, were 86.6% for WO₃ and 62% for WO₃-TiO₂. Therefore, the composite films suffered from relatively more surface recombination but generated larger photocurrents, which resulted in overall improved photoactivity. Full article

Resistant biofilms formed by Staphylococcus aureus on medical devices pose a constant medical threat. A promising alternative to tackle this problem is photodynamic inactivation (PDI). This study focuses on a polyurethane (PU) material with an antimicrobial surface consisting of a composite based on silicate, polycation, and erythrosine B (EryB). The composite was characterized using X-ray diffraction and spectroscopy methods. Anti-biofilm effectiveness was determined after PDI by calculation of CFU mL⁻¹. The liquid PU precursors penetrated a thin silicate film resulting in effective binding of the PU/silicate composite and the PU bulk phases. The incorporation of EryB into the composite matrix did not significantly alter the spectral properties or photoactivity of the dye. A green LED lamp and laser were used for PDI, while irradiation was performed for different periods. Preliminary experiments with EryB solutions on planktonic cells and biofilms optimized the conditions for PDI on the nanocomposite materials. Significant eradication of S. aureus biofilm on the composite surface was achieved by irradiation with an LED lamp and laser for 1.5 h and 10 min, respectively, resulting in a 10,000-fold reduction in biofilm growth. These results demonstrate potential for the development of antimicrobial polymer surfaces for modification of medical materials and devices. Full article

Doping titanium dioxide has become a strategy for enhancing its properties and reducing its recombination issues, with the aim of increasing its efficiency in photocatalytic processes. In this context, this work studied its deposition over glass substrates using a sol–gel dip coating methodology. The effect of doping TiO₂ with Zirconium cations in low molar concentrations (0.01, 0.05, 0.1%) in terms of its structural and optical properties was evaluated. The structural characterization confirmed the formation of amorphous thin films with Zr introduced into the TiO₂ cell (confirmed by XPS characterization), in addition to increasing and defining the formed particles and their size slightly. These changes resulted in a decrease in the transmittance percentage and their energy band gap. Otherwise, their photocatalytic properties were evaluated in hydrogen production using ethanol as a sacrificial agent and UV irradiation. The hydrogen evolution increased as a function of the Zr doping, the sample with the largest Zr concentration (0.1% mol) being the most efficient, evolving 38.6 mmolcm⁻² of this gas. Zr doping favored the formation of defects in TiO₂, being responsible for this enhancement in photoactivity. Full article

Cu₂O homojunction solar cells were fabricated using potentiostatic electrodeposition technique. n-Cu₂O thin films were grown in an acetate bath while p-Cu₂O thin films were grown in a lactate bath. In the growth of n-Cu₂O films, cupric acetate concentration, pH and temperature of the bath, deposition potential and duration (film thickness) and annealing temperature were investigated. In the growth of p-Cu₂O on n-Cu₂O, concentration of copper sulphate and lactic acid solutions, pH and temperature of the bath, deposition potential and duration were investigated. In addition, the procedure of sulfidation of p-Cu₂O film surface using (NH₄)₂S vapor, before depositing Au front contact, was also optimized to enhance the photoactive performance. The structural, morphological and optoelectronic properties of the Cu₂O films were investigated using scanning electron microscopy (SEMs), high energy X-ray diffraction (HEXRD), hard X-ray photoelectron spectroscopy (HAXPES), spectral response and current–voltage (J-V) measurements. The best Cu₂O homojunction solar cell exhibited V_oc = 460 mV, J_sc = 12.99 mA·cm⁻², FF = 42% and η = 2.51%, under AM 1.5 illumination. Efficiency enhancement with the record high J_sc value for the Cu₂O homojunction solar cell has mainly been due to the optimization of pH of the n-Cu₂O deposition bath and lactic acid concentration of the p-Cu₂O deposition bath. Full article

Herein, we present the preparation of solid-state photoactive starches with a large Stokes shift, along with the resulting materials. In this investigation, 2-(2′-hydroxyphenyl)benzazole derivatives responsive to intramolecular proton transfer in the excited state (ESIPT) were covalently bonded to the polymeric structure of starch through a reaction involving an isothiocyanate group and the hydroxyl groups of starch. These compounds exhibit absorption at approximately 350 nm, which is related to fully spin- and symmetry-allowed π → π* electronic transitions, and solid-state fluorescence at approximately 500 nm, which features a significant separation between the absorption and emission maxima (~9000 cm⁻¹). Due to the minimal use of fluorophores in functionalized starch preparation, this modification does not affect the original properties of the starch. Finally, photoactive starch-based films with significantly high transparency were successfully produced. Full article

Organic solar cells (OSCs) are becoming increasingly popular in the scientific community because of their many desirable properties. These features include solution processability, low weight, low cost, and the ability to process on a wide scale using roll-to-roll technology. Enhancing the efficiency of photovoltaic systems, particularly high-performance OSCs, requires study into not only material design but also interface engineering. This study demonstrated that two different types of OSCs based on the PTB7-Th:IEICO-4F and PM6:Y6 active layers use a ZnO bilayer electron transport layer (ETL). The ZnO bilayer ETL comprises a ZnO nanoparticle (ZnO NP) and a ZnO layer created from a sol-gel. The effect of incorporating ZnO NPs into the electron transport layer (ETL) was studied; in particular, the effects on the electrical, optical, and morphological properties of the initial ZnO ETL were analyzed. The ability of ZnO films to carry charges is improved by the addition of ZnO nanoparticles (NPs), which increase their conductivity. The bilayer structure had better crystallinity and a smoother film surface than the single-layer sol-gel ZnO ETL. This led to a consistent and strong interfacial connection between the photoactive layer and the electron transport layer (ETL). Therefore, inverted organic solar cells (OSCs) with PTB7-Th:IEICO-4F and PM6:Y6 as photoactive layers exhibit improved power conversion efficiency and other photovoltaic properties when using the bilayer technique. Full article