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Third-order nonlinearity and optical limiting properties of sol–gel-based bromophenol blue dye immobilized in silica–titania nanohybrid
摘要： Silica–titania (ST) nanohybrid and bromophenol blue (BPB) immobilized ST nanohybrid matrix are synthesized by low-temperature sol–gel route. The in?uence of BPB on the structural, morphological, and nonlinear optical properties of silica–titania nanohybrid was investigated by fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), atomic force microscopy (AFM), and z-scan technique. FTIR analysis con?rms the chemical bonding between hydrophobic BPB dye species and hydrophilic type ST nanohybrid matrix. TEM and AFM analysis shows that the synthesized immobilized nanohybrid has inter-dispersed structure with average particle size of 0.8 ± 0.3 nm, smooth morphology, and low average surface roughness ~4.57 nm. The immobilization of BPB greatly improves the nonlinear refraction response and the nonlinear refractive index increases from 4.8 × 10–9 cm2/W to 451.9 × 10–9 cm2/W. Reverse saturable absorption is observed in both BPB and BPB/ST nanohybrid. However, the magnitude of nonlinear absorption coef?cient in BPB/ST is lower than the BPB dye due to the occurrence of saturable absorption of the ST matrix. The optical limiting (OL) behavior of the BPB/ST nanohybrid reveals the low OL threshold at 0.33 kW/cm2. The synthesized BPB/ST nanohybrid has potential as an optical limiters for safety of photonic and optoelectronic devices under low-powered CW laser.
关键词： Optoelectronics,Silica–titania nanohybrid,Saturable absorption,Bromophenol blue dye,Structural analysis
更新于2025-09-19 17:15:36
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Solution-Processed Anatase Titania Nanowires: From Hyperbranched Design to Optoelectronic Applications
摘要： The utilization of solar energy and the development of its related optoelectronic devices have become more important than ever. Solar cells or photoelectrochemical (PEC) cells that require the design of light harvesting assemblies for efficiently converting solar light into electricity or solar fuels are of particular interest. Semiconductor TiO2, serving as the photoelectrode for photovoltaic devices (e.g., dye- or quantum dot-sensitized solar cells (DSSCs/QDSSCs) or perovskite solar cells (PSCs)) and PEC cells, has aroused intense research interest owing to its inherent characteristics of wide band gap and promising optical and electrical properties. TiO2 nanowires (TNWs) have been widely used in optoelectronic devices due to their unique 1D geometry and salient optical and electrical properties. However, the insufficient surface area resulting from the relatively large diameter of NWs and considerable free space between adjacent NWs restricts their optoelectronic performance. Hence, it is desirable to explore every feasible aspect of TNWs in terms of structural design and optical management, aiming to further improve the performance of optoelectronic devices. In this Account, we present a brief survey of strategies for designing branched or hyperbranched TNW-based photoelectrodes and their applications in solar cells and PEC cells. The general strategies (e.g., alkaline/acid hydrothermal method, lift-off transfer, and self-assembly approach) are discussed to address the challenges associated with fabricating TNWs on transparent conducting oxide (TCO) substrates. A series of strategies to fabricate judiciously designed 3D branched array architectures, including length tuning and sequential surface branched or hyperbranched modification, are proposed. The versatile implantation of the TNWs onto other backbones (nanosheets, nanotubes, hollow spheres, or multilayered electrodes) and substrates (fiber-shaped metal wire or mesh, flexible metal foil, or plastic sheet) is demonstrated to construct a new class of the TNW-embedded composite electrode materials with desired morphological characteristics and optoelectronic properties, for example, favorable energy level alignment for cascade charge transfer and rational homogeneous/heterogeneous interfacial engineering. The functionalities of TNW-based electrodes include enlarged surface area and superior light scattering for maximized light harvesting, as well as facilitated charge transport and suppressed charge recombination for enhanced charge collection, which are promising in optoelectronic fields such as solar cells, photocatalysis, and PEC cells. Beyond TNWs, one can also integrate other types of semiconductor (e.g., Fe2O3 or WO3) NWs into rationally designed structures for preparing novel photocatalytic materials with panchromatic absorption, efficient charge transfer, and excellent catalytic properties. Finally, an insightful perspective for rational design of advanced NW-based materials is provided.
关键词： Solar cells,Hyperbranched design,Anatase titania nanowires,Photoelectrochemical cells,Optoelectronic applications,Solution-processed
更新于2025-09-19 17:15:36
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Favorable manipulation of macrophage/endothelial cell’s functionality and their cross-talk on silicon-doped titania nanotube arrays
摘要： Inflammatory reaction and the functionality of endothelial cells (ECs) on the surface of coronary stents are critical in the prevention of the in-stent restenosis and subsequent neoatherosclerosis. However, the interactions between immune cells and ECs on modified coronary stent surface have long been underestimated. In the present study, silicon (Si)-doped titania nanotube arrays (TNA-Sis) were obtained by a facile anodization of magnetron-sputtered Ti-Si coatings. The synergetic effect of titania nanotube arrays (TNAs) and chemical cues (Si) on the functionality of macrophages (MΦs) /ECs and their cross-talk were investigated. The results indicated that TNA-Sis, in comparison with TNAs alone, not only promoted ECs initial vitality, enhanced the expression of vascular endothelial growth factor (VEGF) and nitric oxide (NO), activated multiple cell signaling pathways (vWF, PECAM, eNOS), but also induced a favorable immune response through the polarization of MΦs to a pro-healing M2 phenotype via the activation of cell autophagy, resulting in the downregulation of inflammatory reaction. The beneficial immune response further facilitated the cross-talk between ECs and MΦs with a profoundly increased functionality of EC on TNA-Sis surfaces. This study demonstrated that the surface coating of TNA-Sis for the coronary stent may be a promising strategy to prevent in-stent restenosis.
关键词： Endothelial cells,Coronary stents,Silicon,Macrophages,Titania nanotube arrays
更新于2025-09-19 17:15:36
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A novel cheap, one-step and facile synthesis of hierarchical TiO2 nanotubes as fast electron transport channels for highly efficient dye-sensitized solar cells
摘要： The well-aligned hierarchical TiO2 nanotubes (HTNTs) have been synthesized by a one-step hydrothermal method employing potassium titanium oxalate, ethanol and H2O, which are strongly adhered onto transparent conducting oxide glass. The preparation is straightforward, cheap and applicative for mass manufacture. The thickness of membranes is changed from 12 to 22 lm by adjusting the reaction time. The HTNTs consist of one-dimensional (1D) long TiO2 nanotube trunks and numerous short TiO2 nanorod branches, which can balance surface area and charge transport. By employing optimized HTNTs for dye-sensitized solar cells, a remarkable power conversion ef?ciency of 9.89% is obtained. The result is superior to P25 (8.34%), because 1D trunk-1D branch structure of HTNTs offers the advantages of strong light-harvesting, directed electron transport, and ef?cient charge collection. The HTNTs may ?nd an underlying application in the manufacture of photovoltaic devices.
关键词： Dye-sensitized solar cell,Titania,Hierarchical structure,Charge transport,Nanotube
更新于2025-09-19 17:13:59
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Topological Aspects of Single-Walled Titania Nanotubes
摘要： In chemical graph theory, a topological index is a numerical representation of a chemical structure while a topological descriptor correlates certain physico-chemical characteristics of underlying chemical compounds besides its numerical representation. Graph theory plays an important role in modeling and designing any chemical network. A large number of properties like physico-chemical properties, thermodynamic properties, chemical activity and biological activity are determined by the chemical applications of graph theory. These properties can be characterized by certain graph invariants referred to as topological indices. In this paper, we discuss the titania nanotube TNT3?m, n(cid:2), titania nanotube TNT6?m, n(cid:2), and computed exact results for degree based topological indices.
关键词： TNT6?m, n(cid:2),titania nanotube,Balaban index,TNT3?m, n(cid:2),forgotten topological index,Zagreb type indices
更新于2025-09-19 17:13:59
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Hybrid TiO2-ZnO Nanomaterials Prepared Using Laser Ablation in Liquid
摘要： Hybrids of semiconductor nanomaterials often demonstrate properties that are superior to those of their components. In this study, we prepared hybrid nanomaterials of TiO2 and ZnO, which are among the most actively studied semiconductors, by means of millisecond-pulsed laser and analyzed how their morphology, particle size, and surface composition depend on preparation conditions. A series of nanomaterials were obtained via sequentially ablating Zn and Ti metal plates (in di?erent sequences) in water, while laser pulses of lower (2.0 J/pulse) and higher (5.0 J/pulse) energy were applied. The properties of laser-produced hybrid TiO2-ZnO nanomaterials were shown to be governed by experimental conditions such as laser pulse width, pulse peak power, and reaction media (either pure water or colloid with nanoparticles). The morphology revealed nanospheres of TiO2 that decorate nanorods of ZnO or ?ower-like aggregates of zinc oxide. Intriguingly, after extended ablation time, titania was found to be self-doped with Ti3+ ions, and the contribution of lower oxidation states of titanium could be controlled by the applied laser pulse energy. The physicochemical characteristics of hybrid nanomaterials were compared with pure ZnO and TiO2 prepared under the same laser conditions.
关键词： ZnO nanorods,TiO2 nanospheres,Ti3+ and Ti2+ doped titania,hybrids TiO2-ZnO,XPS
更新于2025-09-19 17:13:59
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Investigating the Role of Reduced Graphene Oxide as a Universal Additive in Planar Perovskite Solar Cells
摘要： In this work we present the effects of the incorporation of reduced graphene oxide (rGO) nanoflakes into the titania compact layer, the methylammonium lead iodide (CH3NH3PbI3) absorber and the Spiro-MeOTAD hole transporter which are typical components of a planar perovskite solar cell (PSC). The addition of rGO within the TiO2 electron transport layer (ETL) offers fast electron transport rates toward the anode and favors the growth of large, uniform perovskite crystals. When added in MAPbI3, rGO further increases the perovskite grains size and creates a more homogenous and smooth film with enhanced crystallinity, thus improving the power conversion efficiency (PCE) of the corresponding PSC. On the contrary, its presence in Spiro-MeOTAD is detrimental for the cells performance. For the first time in the literature a graphene derivative favors the performance of a MAPbI3–based PSC when incorporated as an additive in both the ETL and the perovskite absorber. As a result, we obtained devices with optimized electrical characteristics, resulting to stabilized 13.6% PCE, outperforming by 20% the reference (rGO-free) ones. Moreover, the presence of rGO offered additional stability to the solar cells which retained 40% of their initial PCE after 50 days of storage in mildly humid, dark environment.
关键词： Reduced graphene oxide,Lead acetate,Planar perovskite solar cells,MAPbI3 absorber,Titania compact layer
更新于2025-09-16 10:30:52
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Characterization of Enzymatically Synthesized Titania Thin Films Using Positron Annihilation Spectroscopy Reveals Lowa??Cost Approach for Organic/Inorganic Photovoltaic Cells
摘要： A new method is developed to produce mesoporous titania thin films at room temperature using the enzyme papain in a dip-coating procedure, providing low-cost titania films in a sustainable manner. Quartz crystal microbalance, positron annihilation Doppler broadening and lifetime spectroscopy, scanning electron microscopy, and X-ray diffraction are used to determine the deposition and structural properties of the films. As-deposited films have low densities ρ ≈ 0.6 g cm?3, contain small micropores and proteins, and exhibit corrugated surfaces. Annealing at temperatures of 300 °C or higher leads to the destruction and evaporation of most of the organic material, resulting in a thickness decrease of 50–60%, more pure titania films with increased density, an increase in micropore size and a decrease in the concentration and size of atomic-scale vacancies. Up to 50 layers could be stacked, allowing easy control over the total layer thickness. Based on these titania films, first test devices consisting of natural dye-sensitized solar cells are produced, that show photovoltaic activity and indicate possibilities for low-cost, accessible, organic production of solar cells. Given the wide range of other applications for titania, this new method is a promising candidate for improving the fabrication of those products with respect to cost, sustainability, and production speed.
关键词： titania,biomineralization,enzymes,positron annihilation,photovoltaics
更新于2025-09-16 10:30:52
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Investigation of nitrogen and iron co-doped TiO2 films synthesized in N2/CH4 via pulsed laser deposition technique
摘要： Nitrogen and iron ions co-doped titania films have been synthesized by PLD technique in nitrogen/methane (N2/CH4) (5:1) media at 1 mbar. Most of the samples are XRD amorphous but a certain amount of crystalline rutile is detected by Raman measurements. The presence of rutile phase only and its low crystallinity degree can be caused by nitrogen doping of oxide matrix. The most intensive VIS absorption and the lowest band gap values are observed for 5% Fe2O3 or Fe3O4 titania films that are supported by the highest nitrogen amount on the surface. The strongest photocatalysts in process of dichromate reduction under either UV or VIS irradiation are shown to be the films obtained from 5% iron oxide in titania target and synthesized at 550 °C as a result of optimal content of Ti–N and Ti–O–Fe structural fragments as revealed by XPS. The presence of Fe3+ and Fe2+ surrounded by oxygen as well as Fe–N bonds is confirmed by XPS data.
关键词： Pulsed laser deposition,Magnetite,Photocatalysis,Hematite,Titania,Nitrogen doping
更新于2025-09-16 10:30:52
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Voids in walls of mesoporous TiO2 anatase nanotubes by controlled formation and annihilation of protonated titanium vacancies
摘要： Amorphous TiO2 nanotubes (TNTs) grown anodically on Ti metal in aqueous electrolytes show a crystallization behaviour strongly dependent on the atmosphere used during annealing at high temperature. In wet oxidizing conditions, the amorphous TNTs walls transform into relatively large and well crystallized anatase-like domains permeated by prismatic voids. On the other hand, crystallization of the amorphous nanotubes under dry reducing conditions induces nanocrystalline aggregates that do not show prismatic voids and exhibit different electronic properties. Supported by density functional theory calculations, it is argued that the formation or absence of voids can be understood in terms of formation and condensation of protonated titanium vacancies. Tunable morphology through defect chemical engineering as such, enables TNTs with increased surface area and catalytic activity, which find potential application in supercapacitors, sensors, photocatalysis, photoelectrochemistry, and dye-sensitized solar cells.
关键词： TiO2 nanotube voids,Titanium oxohydroxide,Supercapacitors,Black titania,Anatase
更新于2025-09-12 10:27:22