Search Results (8)

Polyvinyl alcohol (PVA)/TiO₂/colloidal photonic crystal (CPC) films with photocatalytic properties are presented, where TiO₂ nanoparticles were introduced into the PVA gel network. Such PVA/TiO₂/CPC films possess three-dimensional periodic structures that are supported with a PVA/TiO₂ composite gel. The unique structural color of CPCs can indicate the process of material preparation, adsorption, and desorption. The shift of diffraction peaks of CPCs can be more accurately determined using fiber-optic spectroscopy. The effect of the PVA/TiO₂/CPC catalyst films showed better properties as the degradation of methylene blue (MB) by the PVA/TiO₂/CPC film catalyst in 4 h was 77~90%, while the degradation of MB by the PVA/TiO₂ film was 33% in 4 h, indicating that the photonic crystal structure was 2.3~2.7 times more effective than that of the bulk structure. Full article

Diverse chiral structures observed in nature find applications across various domains, including engineering, chemistry, and medicine. Particularly notable is the optical activity inherent in chiral structures, which has emerged prominently in the field of optics. This phenomenon has led to a wide range of applications, encompassing optical components, catalysts, sensors, and therapeutic interventions. This review summarizes the imitations and applications of naturally occurring chiral structures. Methods for replicating chiral architectures found in nature have evolved with specific research goals. This review primarily focuses on a top-down approach and provides a summary of recent research advancements. In the latter part of this review, we will engage in discussions regarding the diverse array of applications resulting from imitating chiral structures, from the optical activity in photonic crystals to applications spanning light-emitting devices. Furthermore, we will delve into the applications of biorecognition and therapeutic methodologies, comprehensively examining and deliberating upon the multifaceted utility of chiral structures. Full article

For a safe environment, humanity should be oriented towards renewable energy technology. Water splitting (WS), utilizing a photoelectrode with suitable thickness, morphology, and conductivity, is essential for efficient hydrogen production. In this report, iridium oxide (IrO_x) films of high conductivity were spin-cast on glass substrates. FE-SEM showed that the films are of nanorod morphology and different thicknesses. UV-Vis spectra indicated that the absorption and reflectance of the films depend on their thickness. The optical band gap (E_g) was increased from 2.925 eV to 3.07 eV by varying the spin speed (SS) of the substrates in a range of 1.5 × 10³–4.5 × 10³ rpm. It was clear from the micro-Raman spectra that the films were amorphous. The E_g vibrational mode of Ir–O stretching was red-shifted from 563 cm⁻¹ (for the rutile IrO₂ single crystal) to 553 cm⁻¹. The IrO_x films were used to develop photoelectrochemical (PEC) hydrogen production catalysts in 0.5M of sodium sulfite heptahydrate Na₂SO₃·7H₂O (2-electrode system), which exhibits higher hydrogen evaluation (HE) reaction activity, which is proportional to the thickness and absorbance of the used IrO_x photocathode, as it showed an incident photon-to-current efficiency (IPCE%) of 7.069% at 390 nm and −1 V. Photocurrent density (Jph = 2.38 mA/cm² at −1 V vs. platinum) and PEC hydrogen generation rate (83.68 mmol/ h cm² at 1 V) are the best characteristics of the best electrode (the thickest and most absorbent IrO_x photocathode). At −1 V and 500 nm, the absorbed photon-to-current conversion efficiency (APCE%) was 7.84%. Electrode stability, thermodynamic factors, solar-to-hydrogen conversion efficiency (STH), and electrochemical impedance spectroscopies (EISs) were also studied. Full article

Indoor toxic volatile organic compounds (VOCs) pollution is a serious threat to people’s health and toluene is a typical representative. In this study, we developed a composite photocatalyst of carbon nitride quantum dots (CNQDs) in situ-doped TiO₂ inverse opal TiO₂ IO for efficient degradation of toluene. The catalyst was fabricated using a sol-gel method with colloidal photonic crystals as the template. The as-prepared catalyst exhibited excellent photocatalytic performance for degradation of toluene. After 6 h of simulated sunlight irradiation, 93% of toluene can be converted into non-toxic products CO₂ and H₂O, while only 37% of toluene is degraded over commercial P25 in the same condition. This greatly enhanced photocatalytic activity results from two aspects: (i) the inverse opal structure enhances the light harvesting while providing adequate surface area for effective oxidation reactions; (ii) the incorporation of CNQDs in the framework of TiO₂ increases visible light absorption and promotes the separation of photo-generated charges. Collectively, highly efficient photocatalytic degradation of toluene has been achieved. In addition, it can be expanded to efficient degradation of organic pollutants in liquid phase such as phenol and Rhodamine B. This study provides a green, energy saving solution for indoor toxic VOCs removal as well as for the treatment of organic wastewater. Full article

Graphene, graphene oxide, reduced graphene oxide and their composites with various compounds/materials have high potential for substantial impact as cheap photocatalysts, which is essential to meet the demands of global activity, offering the advantage of utilizing “green” solar energy. Accordingly, graphene-based materials might help to reduce reliance on fossil fuel supplies and facile remediation routes to achieve clean environment and pure water. This review presents recent developments of graphene-based semiconductor photocatalysts, including novel composites with faceted particles, photonic crystals, and nanotubes/nanowires, where the enhancement of activity mechanism is associated with a synergistic effect resulting from the presence of graphene structure. Moreover, antimicrobial potential (highly needed these days), and facile recovery/reuse of photocatalysts by magnetic field have been addresses as very important issue for future commercialization. It is believed that graphene materials should be available soon in the market, especially because of constantly decreasing prices of graphene, vis response, excellent charge transfer ability, and thus high and broad photocatalytic activity against both organic pollutants and microorganisms. Full article

Semiconductor photocatalysts have attracted a great amount of multidiscipline research due to their distinctive potential for solar-to-chemical-energy conversion applications, ranging from water and air purification to hydrogen and chemical fuel production. This unique diversity of photoinduced applications has spurred major research efforts on the rational design and development of photocatalytic materials with tailored structural, morphological, and optoelectronic properties in order to promote solar light harvesting and alleviate photogenerated electron-hole recombination and the concomitant low quantum efficiency. This book presents a collection of original research articles on advanced photocatalytic materials synthesized by novel fabrication approaches and/or appropriate modifications that improve their performance for target photocatalytic applications such as water (cyanobacterial toxins, antibiotics, phenols, and dyes) and air (NO_x and volatile organic compounds) pollutant degradation, hydrogen evolution, and hydrogen peroxide production by photoelectrochemical cells. Full article

Some co-catalyst nanoparticles can enhance the activity of photocatalysts due to prolonging the charge separation lifetime by promoting the electron or hole transfer. CuO particles were prepared from an aqueous solution of copper (II) nitrate at 351 K on a TiO₂ surface by a photocatalytic reaction and heating at 573 or 673 K. The amount and size of the particles deposited during the photocatalytic reaction can be controlled by changing the amount of the irradiated photons. The CuO crystals with about 50−250 nm-sized particles were formed. Nitrate ions were reduced to nitrite ions in the solution by the photocatalytic activity of the TiO₂, and water was simultaneously transformed into hydroxide ions. An increase in the basicity on the TiO₂ surface induced formation of a copper hydroxide. The copper hydroxide was subsequently dehydrated and transformed into CuO by heating. The TiO₂ loading of a small amount of CuO demonstrated a higher photocatalytic activity for methylene blue degradation compared to the original TiO₂ due to the electron transfer from the TiO₂ conduction bands to the CuO conduction band. Full article

Multiple-phenyl phosphorous compounds are a group of chemical materials that have been used as reactants, pharmaceutical intermediates, extractants, and catalysts in organic synthetic reactions. However, the crystal growth of bulk crystals of multiple-phenyl phosphorous compounds, which may expand their applications in photonics technology, have been largely overlooked. In this article, the crystal growth of tetraphenylphosphonium bromide (TPPB) has been studied in organic solvents and water. The crystal structures and crystallization features are analyzed by X-ray diffraction data. By a slow temperature-lowering method, a single-crystal of TPPB (2H₂O) with the size of 27 × 20 × 20 mm³ has been obtained in water. The basic thermal and optical properties were characterized. We find that the TPPB (2H₂O) crystal shows excellent transparent property in the near-IR region. Large Raman shifts and strong Raman scattering intensity indicate that TPPB is a potential candidate in Raman-scattering-based nonlinearity applications. Full article