Colloidal TiO2 Research Articles

Colloidal TiO2 nanocrystals with engineered defectivity and optical properties.

Partially reduced forms of titanium dioxide (sometimes called "black" titania) have attracted widespread interest as promising photocatalysts of oxidation due to their absorption in the visible region. The main approaches to produce it rely on postprocessing at high temperatures (up to 800 °C) and high pressures (up to 40 bar) or on highly reactive precursors (e.g., TiH2), and yield powders with poorly controlled sizes, shapes, defect concentrations and distributions. We describe an approach for the one-step synthesis of TiO2 colloidal nanocrystals at atmospheric pressure and temperatures as low as 280 °C. The temperature of the reaction allows the density of oxygen vacancies to be controlled by nearly two orders of magnitude independently of their size, shape, or colloidal stability. This synthetic pathway appears to produce vacancies that are homogeneously distributed in the nanocrystals, rather than being concentrated in an amorphous shell. As a result, the defects are protected from oxidation and result in stable optical properties in oxidizing environments.

Reaction-sintered zircon-based nanostructured coatings obtained by suspension plasma spraying

Zircon (ZrSiO4) is an inexpensive and widely available material with excellent thermal properties that makes it an ideal candidate for thermal barrier coatings. Previous works have demonstrated the feasibility of obtaining coatings with a high retention of zircon by plasma spraying of ZrSiO4 and ZrSiO4/ZrO2 suspensions.Suspensions of ZrSiO4/Al2O3 and ZrSiO4/TiO2 were produced by dispersing a micrometric zircon powder into alumina and titania colloidal sols, optimising their colloidal stability and rheological behaviour. Optimised slurries were plasma sprayed onto metallic substrates, obtaining coatings with the typical morphologies obtained by suspension plasma spraying (SPS). Nanostructured coatings with nanoparticles embedded in the molten matrix were obtained at higher proportions of sprayed colloidal sol. The high retention of ZrSiO4 in the final coatings and the formation of new crystallographic phases of mullite and zirconium titanate by reaction of the by-products of zircon decomposition (SiO2 and ZrO2) and the Al2O3 and TiO2 colloids was demonstrated.

One-step fabrication of a self-driven point-of-care chip by femtosecond laser direct writing and its application in cancer cell H2O2 detection via semiconductor-based SERS

Self-driven microfluidic systems have attracted significant attention and demonstrated great potential in the field of point-of-care (POC) testing due to their device simplicity, low power consumption, increased portability, and reduced sample consumption. To develop POC detection chips with diverse characteristics that meet different requirements, there is a strong demand for feasible strategies that enable easy operation and reduce processing time. Here, a one-step processing approach using femtosecond laser direct writing technology was proposed to fabricate a capillary-actuated POC microfluidic chip. The driving force of the chip is highly dependent on its surface wettability, which can be easily adjusted by changing the laser processing parameters. This POC microfluidic chip allowed for the detection of intracellular H2O2 through a catalytic reaction system that incorporated 5-aminosalicylic acid -sensitized colloidal TiO2 nanoparticles and horse radish peroxidase, with integrating semiconductor-based surface-enhanced Raman scattering (SERS) quantitative technique. The concentration of H2O2 was determined by the SERS signal of the catalytic products in the microfluidic chip, resulting in rapid detection with minimal sample consumption. Our method provides a simple, feasible, and alternative strategy for POC testing of H2O2, with a linear range of 10−2∼10−6 M and a limit of detection of 0.55 μM. This approach was successfully applied to rapid detection of intracellular H2O2 in MCF-7 breast cancer cells with high sensitivity and minimal sample consumption. Additionally, this study not only demonstrates the exceptional advantages of femtosecond laser processing technology in fabricating diverse microfluidic chips for various applications, but also presents an efficient POC testing strategy for detecting cell signaling molecules.

In-Situ Synthesis of CuO/TiO2 Nanocomposite Onto Amine Modified Cotton Fabric for Antibacterial Durability and UV Protection

ABSTRACT In this research work, we explore antibacterial activity and the UV-protection of cotton fabric functionalized with copper oxide-titanium dioxide nano composites particles (CuO+TiO2 NCPs). Cotton fabrics (Cot) were treated with L-methionine (Am) and functionalized with bimetallic CuO+TiO2 NCPs by pad and rolling technique. Cu(NO3)2 and titanium isopropoxide (TIP) were used as sources of Cu(OH)2 and TiO2 colloid respectively, which were then converted into CuO and TiO2 nanoparticles (NPs) for making antibacterial and UV-protective cotton. The method yielded a crystallite size of CuO and TiO2 NPs of 18.09 and 32.5 nm, respectively. FTIR, Raman spectroscopy, High-resolution scanning electron microscopy-Energy dispersive Spectroscopy (HRSEM), (EDS), X-ray photo spectroscopy (XPS), thermal gravimetric analysis (TGA), and XRD were used to analyze the functional group, morphology, chemical composition, thermal stability and crystalline structure of the functionalized cotton fabric samples. The results showed that an esterification reaction occurred between Am and OH in cotton fabric, which further enhanced the binding of NCPs. AmCot-CuO+TiO2 NCPs exhibit outstanding antibacterial activity against gram-positive S. aureus and gram-negative E. coli. The UV protection factor (UPF) for AmCot-CuO+TiO2 NCPs reached 50+; thus, multifunctional cotton fabrics with excellent antibacterial and anti-ultraviolet properties were obtained.

Effect of the Photoreduction Process on the Self-Cleaning and Antibacterial Activity of Au-Doped TiO2 Colloids on Cotton Fabric.

This study aims at understanding the effect of the photoreduction process during the synthesis of gold (Au)-doped TiO2 colloids on the conferred functionalities on cotton fabrics. TiO2/Au and TiO2/Au/SiO2 colloids were synthesized through the sol-gel method with and without undergoing the photoreduction step based on different molar ratios of Au:Ti (0.001 and 0.01) and TiO2/SiO2 (1:1 and 1:2.3). The colloids were applied to cotton fabrics, and the obtained photocatalytic self-cleaning, wet photocatalytic activity, UV protection, and antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria were investigated. The obtained results demonstrated that the photoreduction of Au weakened the self-cleaning effect and reduced the photocatalytic activity of coated fabrics. Also, an excess amount of Au deteriorated the photocatalytic activity under both UV and visible light. The most efficient self-cleaning effect was obtained on fabrics coated with a ternary TiO2/Au/SiO2 colloid containing ionic Au, where it decomposed coffee and red-wine stains after 3 h of illumination. Adding silica (SiO2) made the fabrics superhydrophilic and led to greater methylene blue (MB) dye adsorption, a faster dye degradation pace, and more efficient stain removal. Moreover, the photoreduction process affected the size of Au nanoparticles (NPs), weakened the antibacterial activity of fabrics against both types of tested bacteria, and modestly increased the UV protection. In general, the photoactivity of Au-doped colloids was influenced by the synthesis method, the ionic and metallic states of the Au dopant, the concentration of the Au dopant, and the presence and concentration of silica.

Synthesis and stabilities of Fe, Ni and Zn oxide incorporated colloidal TiO2

Owing to the unique physical and chemical characteristics of nanoparticles (NPs), their use in the manufacturing of commercial products is on the rise. The future will see an increasing quantity of NPs being discharged into our surroundings. This is precisely why it is important to understand their stability under changing conditions. This research examined the role of added Fe (III), Ni (II) and Zn (II) on the formation and stabilities of aqueous colloids of TiO2 particles. To the best of our knowledge, this is the first attempt to investigate the stability of lab synthesized composite NPs. The study confirmed that both the stability and environmental fate of metal oxide and mixed metal oxide NPs depends on the composition of aqueous environment. This can add more to the general understanding of NPs while paving way for exploring the stability and environmental fate of various mixed metal oxide/composites NPs as previous studies explored only commercially prepared plain NPs. TiO2 and TiO2-Fe2O3, TiO2-NiO, and TiO2-ZnO were synthesized following reported methods. Different characterization techniques including transmission electron microscope (TEM), x-rays diffraction (XRD), energy dispersive X-ray (EDX) analysis, and dynamic light scattering (DLS) were used to confirm the surface morphology, phase, elemental composition, and hydrodynamic (Dh) size of synthesized TiO2 particles. As-synthesized TiO2 and its various forms (TiO2-Fe2O3, TiO2-NiO, and TiO2-ZnO) showed rapid aggregation behavior in solutions, which is a sign of less or no threat to human health and the environment. Among the synthesized composites, TiO2-Fe2O3 showed the highest stability across all the methods utilized in this research. For all the approaches employed in dispersing aggregates of TiO2 NPs and their composites in solution, homogenization method displayed the highest efficiency. Moreover, the addition of an electrolyte i.e., KCl into the particle suspensions has affected the ionic strength of these suspensions resulting in an increased aggregation due to the shifting of ions-particles equilibrium. Thus, the formation of composites on TiO2 can govern both the stability and environmental fate of TiO2 particles under various aqueous environments.

Elucidating the structural and spectroscopic attributes of titania-iron oxide (TiO2-([formula omitted]-Fe2O3)) nanocomposites: Showcasing a pulsed laser ablation in liquid approach

Various nanomaterials with tailored photo-electrochemical and physicochemical attributes became viable for the photo-catalysis and sensors applications. Thus, some new types of TiO2-(α-Fe2O3) nanocomposites were made via the pulse laser ablation in liquid method. These nanocomposites at each value of laser fluence were obtained by mixing the colloidal TiO2 nanoparticles and colloidal (α-Fe2O3) nanoparticles at equal ratio. The stability, structures, morphologies, and optical characteristics of the produced nanocomposites (suspended in deionized water) were customized by changing the laser fluence from 3.5–17.7 J cm−2. The high-resolution transmission electron microscopy micrographs showed the existence of homogeneous dispersion of spherical nanocrystallites (mean diameter 12.4 ± 6.0 nm) in the colloidal suspension. Both X-ray diffraction and Fourier transform infrared profiles of the specimen verified their purity and good nanocrystallinity. Two optical absorption peaks were probed in the range of 240 to 380 nm convoyed by a blue-shift. The spectral edge related to UV–Vis absorption was used to estimate the optical band gap of these nanocomposites. TiO2-(α-Fe2O3) nanocomposites made at optimum laser fluence (10.6 J cm−2) exhibited strong fluorescence with the life time decay of 3.64 μs, indicating the electronic density of states modification due to quantum size effects. The presence of Fe, Ti, and O in the X-ray photoelectron spectroscopy spectra reaffirmed the samples purity. The measured strong negative zeta potential (-33.1 mV) of the optimum TiO2-(α-Fe2O3) nanocomposites confirmed their excellent stability in the colloidal suspension. In short, these nanocomposites may be advantageous as good photo-catalysts for waste water treatment and photo-electrochemical uses.

Improved charge transfer on heterophase colloidal TiO2 with interaction between inserted atom and peroxysulfate for refractive antibiotics removal under visible light

Photocatalysis is a sustainable technique having unparalleled advantages in wastewater treatment. Its catalytic efficiency can be greatly enhanced by combining with Fenton-like reactions, e.g., persulfate activation-based oxidation. However, the performance of this coupled technique is mainly limited by the development of catalysts that connect two catalytic reaction systems. Herein, heterophase colloidal TiO2 with insertion of heteroatoms C and N was synthesized as a physicochemical stable visible light responsive photocatalyst enabling persulfate activation to selectively generate strong radicals of •OH and SO4•− for removal of refractory pollutants (i.e., florfenicol) via an enhanced electron-transfer route. The optoelectronic characterizations and DFT calculation reveal the changes of band structure, charge transfer and migration pathway after C, N elements inserted into heterophase crystal lattice. The N site favors both separation of photogenerated charge carriers and activation of persulfate, and the coupling mechanism is disclosed in detail. Meanwhile, the participation of the strong radicals in the florfenicol decomposition and the toxicity of intermediates are discussed. This work highlights the importance of non-transition metal oxide-based catalysts for synergistic photocatalysis and persulfate activation and provides a deep insight into the synergistic mechanisms in generating strong radicals at the molecular level.

The multivariate interaction between Au and TiO2 colloids: the role of surface potential, concentration, and defects.

The established DLVO theory explains colloidal stability by the electrostatic repulsion between electrical double layers. While the routinely measured zeta potential can estimate the charges of double layers, it is only an average surface property which might deviate from the local environment. Moreover, other factors such as the ionic strength and the presence of defects should also be considered. To investigate this multivariate problem, here we model the interaction between a negatively charged Au particle and a negatively charged TiO2 surface containing positive/neutral defects (e.g. surface hydroxyls) based on the finite element method, over 6000 conditions of these 6 parameters: VPart (particle potential), VSurf (surface potential), VDef (defect potential), DD (defect density), Conc (salt concentration), and R (particle radius). Using logistic regression, the relative importance of these factors is determined: VSurf > VPart > DD > Conc > R > VDef, which agrees with the conventional wisdom that the surface (and zeta) potential is indeed the most decisive descriptor for colloidal interactions, and the salt concentration is also important for charge screening. However, when defects are present, it appears that their density is more influential than their potential. To predict the fate of interactions more confidently with all the factors, we train a support vector machine (SVM) with the simulation data, which achieves 97% accuracy in determining whether adsorption is favorable on the support. The trained SVM including a graphical user interface for querying the prediction is freely available online for comparing with other materials and models. We anticipate that our model can stimulate further colloidal studies examining the importance of the local environment, while simultaneously considering multiple factors.

Colloidal TiO2-Modified Mesoporous Electron Transport Layer in Perovskite Solar Cells

The electron transport layer (ETL) is a crucial part in perovskite solar cells (PSC) as it specifically governs the charge extraction at the perovskite/ETL interface. In this study, methylammonium lead iodide-based PSCs with an n-i-p structure were fabricated and modified by adding colloidal TiO2 into the mesoporous TiO2 film as ETL. The effect of the colloidal TiO2 addition on the PSC performance was investigated for ETL comprising different types of TiO2 particles, i.e. P25 and anatase TiO2. Despite producing lower performance than the PSC made with commercial paste, the power conversion efficiency of the PSCs could be improved with the introduction of colloidal TiO2 solution. An optimum condition was observed depending on the type of TiO2 particle, where the best performing device was achieved with colloidal TiO2 of 0.4 and 0.2 mL for P25 and anatase TiO2, respectively. The amount of colloidal TiO2 in samples with P25 overall had less impact than the samples with anatase TiO2.

Processing of kaolin micro-composite functional fillers for enhancing the near-IR reflective performance of polyurethane resin coatings

Polyurethane (PU) resin products meant for protective coatings are chemically composed of two-phase microstructures; soft ‘polyols’ and hard ‘diisocyanates and chain extenders’. For durable high-performance specialty PU coatings, their surface heat reflectance property is to be enhanced; otherwise, the absorption of solar heat energy eventually generates heat build-up that finally induces microstructural changes and chemical degradation. Hence, in this work, an attempt is made to improve the poor IR reflectance property of PU resin by incorporating kaolin micro-composite functional fillers. In this study, kaolin delamination was first carried out using alumina and zirconia milling media. Delaminated kaolin was treated with colloidal oxides, SiO2, Al2O3, and TiO2, to produce kaolin micro-composite fillers. The filler effect, chemical interaction, heat build-up, scratch resistance, and hydrophobic properties were examined, and results were presented. The study confirmed that when Al2O3-modified kaolin micro-composites improved the scratch resistance, the incorporation of 10 mass% mixed oxide kaolin micro-composite fillers enhanced the NIR reflecting property of PU coats from 4% to 53%. A facile strategy to enhance the solar heat shielding property of PU top coats for obtaining long-life durable protective coatings is presented in this work.

Partial Hydrolysis of Diphosphonate Ester During the Formation of Hybrid TiO2 Nanoparticles: Role of Acid Concentration.

The hydrolysis of the phosphonate ester linker during the synthesis of hybrid (organic-inorganic) TiO2 nanoparticles is important when forming porous hybrid organic-inorganic metal phosphonates. In the present work, a method was utilized to control the in-situ partial hydrolysis of diphosphonate ester in the presence of a titania precursor as a function of acid content, and its impact on the hybrid nanoparticles was assessed. Organodiphosphonate esters, and more specific, their hydrolysis degree during the formation of hybrid organic-inorganic metal oxide nanoparticles, are relatively under explored as linkers. Here, a detailed analysis on the hydrolysis of tetraethyl propylene diphosphonate ester (TEPD) as diphosphonate linker to produce hybrid TiO2 nanoparticles is discussed as a function of acid content. Quantitative solution NMR spectroscopy revealed that during the synthesis of TiO2 nanoparticles, an increase in acid concentration introduces a higher degree of partial hydrolysis of the TEPD linker into diverse acid/ester derivatives of TEPD. Increasing the HCl/Ti ratio from 1 to 3, resulted in an increase in degree of partial hydrolysis of the TEPD linker in solution from 4 % to 18.8 % under the applied conditions. As a result of the difference in partial hydrolysis, the linker-TiO2 bonding was altered. Upon subsequent drying of the colloidal TiO2 solution, different textures, at nanoscale and macroscopic scale, were obtained dependent on the HCl/Ti ratio and thus the degree of hydrolysis of TEPD. Understanding such linker-TiO2 nanoparticle surface dynamics is crucial for making hybrid organic-inorganic materials (i. e. (porous) metal phosphonates) employed in applications such as electronic/photonic devices, separation technology and heterogeneous catalysis.

Colloidal TiO2 Nanorod Films Deposited Using the MAPLE Technique: Role of the Organic Capping and Absence of Characteristic Surface Patterns

Thin films of titanium dioxide (TiO2) nanocrystals, widely acknowledged for their unique physical-chemical properties and functionalities, are used in disparate technological fields, including photovoltaics, sensing, environmental remediation and energy storage. In this paper, the preparation of thin films consisting of anatase-phase TiO2 nanorods deposited using the matrix-assisted pulsed laser evaporation (MAPLE) technique and their characterization in terms of morphology, elemental composition and wettability are presented and discussed. Particular attention is paid to the effects of the laser fluence, varied over a broad range (F = 25, 50, 100 mJ/cm2), and to the role of the capping surfactants bound to the surface of the nanorod precursors. Whereas increasing fluence favored a partial removal of the surface-bound surfactants, a post-growth UV-light-driven photocatalytic treatment of the films was found to be necessary to reduce the incorporated fraction of organics to a further substantial extent. It was noteworthy that, under our experimental conditions, the distinctive surface patterns and roughness that commonly degrade the morphology of films deposited using the MAPLE technique were not observable. This previously unreported experimental evidence was rationalized on the basis of the interaction dynamics between solvent/solute droplets ejected from the laser-irradiated target and the rough surfaces of the growing film.

Stabilization of [BMIM][PF6] ionic liquid membrane in structurally optimized multilayer ceramic support through aqueous DEA solution for CO2/CH4 separation

The stability of the ceramic supported liquid membranes (SLMs) is one of the most interesting research subjects. In this work, the SLMs’ stability for CO2/CH4 separation was investigated. Following pressing α-Al2O3 substrates at 400, 600, and 800 bar, colloidal and polymeric TiO2 intermediate and top layers were coated. Aqueous diethanolamine (DEA) solution was used as solvent in the SLM to optimize support structure based on CO2/CH4 separation performance. The pressed support at 800 bar and coated with TiO2 demonstrated best performance and selected for further study. Subsequently, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid (IL) was immobilized inside the selected support and used as the supported ionic liquid membrane (SILM) for CO2/CH4 separation. The SILM separation performance was evaluated under different pressures and temperatures. Temperature was found to has greater effect than pressure due to a decrease in IL's viscosity and an increase in penetrant diffusivity. At 25 °C and 1 bar, SILM exhibited consistent and reliable performance as CO2 and CH4 permeabilities of 244.0 and 7.4 Barrer, respectively, and CO2/CH4 selectivity of 33.0 over 6 h. The findings contribute to understanding the implementation of multilayer ceramic SILMs for CO2/CH4 separation and highlight its potential along with opening up new avenues.

"ARALASH ERITUVCHI MUHITIDA BIR XIL SHAKLDAGI TiO2 KOLLOID ZARRACHALARININING SINTEZI VA MORFOGRAFIYASI"

"ARALASH ERITUVCHI MUHITIDA BIR XIL SHAKLDAGI TiO2 KOLLOID ZARRACHALARININING SINTEZI VA MORFOGRAFIYASI"

Colloidal Cu-doped TiO2 nanocrystals containing oxygen vacancies for highly-efficient photocatalytic degradation of benzene and antibacterial

Development of suitable colloidal photocatalysts with excellent photocatalytic performance under visible light is essential for indoor environmental remediation. In this study, colloidal Cu-doped TiO2 (Cu-TiO2) nanocrystals containing oxygen vacancies (OVs) were synthesized by a facile sol-hydrothermal method and their photocatalytic performances for benzene degradation and antibacterial were investigated. Characterization results revealed that the doping of Cu induced grain size reduction and bandgap narrowing of TiO2 nanocrystals, as well as the formation of abundant OVs in the TiO2 crystal structure, resulting in enhanced light absorption capacity and charge carrier separation efficiency. The optimized colloidal Cu-TiO2 nanocrystals could achieve a maximum degradation rate constant of 0.364 h−1 for the photocatalytic degradation of benzene and a high antibacterial rate of more than 99.99% against both Escherichia coli and Staphylococcus aureus, which were far superior to those of the pristine TiO2. The effects of Cu dopants and OVs on the band structure of TiO2 were revealed by density functional theory (DFT) calculations combined with experimental characterizations, and a possible mechanism for the enhancement of Cu-TiO2 photocatalytic performance was proposed. This work offers a promising method for the synthesis of colloidal TiO2-based nanocrystals with excellent photocatalytic performances for the practical application in indoor environmental remediation.

Photochromism of TiO2 Nanoparticles Doped with Molybdenum Ions: Neutral Color Change from Colorless to Black via Gray.

Transition metal oxide nanoparticles have been extensively studied for the development of smart windows which are expected to be a promising technology to save energy in buildings. However, most of them turn blue under UV irradiation. Since the blue coloration affects the color of objects through the windows, the development of materials with a neutral color which hardly disturbs the view is more beneficial. In this work, we prepared a colorless-transparent TiO2 colloidal solution containing Mo6+ ions (Mo-TiO2), which turns black via gray in a nitrogen atmosphere under UV irradiation. An absorption peak was observed at 535 nm, which increased with an increase in the UV irradiation time and reached a constant value (Absmax). The Absmax value increased linearly with an increase in the Mo doping amount. We demonstrated that the photochromic behavior of the Mo-TiO2 nanoparticles is completely different from that of pure MoO3 or the mixture of MoO3 and TiO2. In addition, we performed a kinetic study to elucidate the mechanism and found that the coloration rate at the initial stage decreased with an increase in Mo doping amount. Based on the kinetic analysis, the following results are obtained: a color center is formed at a deeper energy level than the Mo dopant level; the number of the color center depends on the Mo doping amount, and the color center traps the photogenerated electrons more rapidly when it is isolated. The black color was bleached by purging the air in the solution. In particular, the gray state which is observed as a transient color is promising for the development of smart windows to shield the sunlight while allowing a clear and undistorted view.

Plasmonic colloidal Nb-doped TiO2 nanocrystals with improved electrochromism in visible-infrared region

Dual-band electrochromic materials can achieve separate modulate of visible and near-infrared (NIR) transmittance, which are important components of smart windows. A promising colloidal Nb-doped TiO2 anatase nanocrystals (NCs) was prepared via the fluoride-assisted synthesis technique. The dual-band electrochromic properties of the NCs are closely related to the localized surface plasmon resonance (LSPR) absorption intensity. With the assistance of fluoride anions, TiO2 NCs can be easily doped with Nb, which is an important discovery. The product is a highly uniform Nb-doped TiO2 colloidal solution. Spectral analysis clarified that the Nb5+ replaced Ti4+, resulting in free carrier generation in the TiO2 conduction band, thereby exciting LSPR. Moreover, Nb-doped TiO2 NCs exhibited outstanding dual-band electrochromic properties including a wide modulation range for visible and NIR region (92.8 % at 620 nm and 75.2 % at 1800 nm) and a high electrochemical cycling stability (83.1 % at 620 nm and 70.3 % at 1800 nm after 1800 cycles). As a novel kind of electrochromic materials, the Nb-doped TiO2 NCs have great potential application for the smart windows.

Computational Study on the Interaction of Iodide Electrolyte/Dye/TiO2 Interface in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) represent an emerging and promising candidate as a future renewable energy resource because of their potential low-cost fabrication cost, environmentally friendly, stability, and efficient solar energy conversion1. However, the intrinsic dye/iodide interaction with the dye on the semiconductor surface in understanding the DSSCs mechanism remains unclear2.In this work, three metal-free organic dyes based on D–π–A architecture were designed and computationally investigated for understanding the DSSCs mechanism and improving its efficiency2 - 4. The different donor groups were employed for the comparative study noted as D1Y, D2Y, and D3Y. This computational study mainly aims at determining the effect of the interaction of the iodide/triiodide with the dye on the semiconductor surface using the first-principles calculations (see scheme.1). We investigated the structural and electronic properties of these dyes when standing alone and being adsorbed on the oxide surface with the iodide electrolyte. Our studies revealed that the incorporation of a strong donor unit in D1Y and D 2 Y dyes in combination with iodide electrolytes on the TiO2 surface provides better adsorption and electronic properties in comparison to those from the dye alone on the TiO2 surface. Analysis of density of states (DOS) revealed that the dye with a strong electron-donating group, mainly D1Y and D2Y with an iodide electrolyte on the surface remarkably upshifts the Fermi energy, thereby improving the efficiency of the DSSCs by increasing the open-circuit voltage (Voc). These current findings provide a valuable hint for attaining a deeper understanding of the intrinsic interaction taking place at the electrolyte/dye/TiO2 interface. References O’Regan, B.; Grätzel, M.A Low-Cost High-Efficiency Solar Cell Based on Dye-Sensitized Colloidal TiO2 Films. Nature 1991, 353, 737– 740.Hailu, M. and J.-C. Jiang Phys. Chem. Chem. Phys., 2020, 22, 26410-26418.Hailu, W.-R. Shie, S. Nachimuthu and J.-C. Jiang, ACS Sustain. Chem. Eng., 2017, 5, 8619-8629.Hailu, M. T. Nguyen and J.-C. Jiang, Phys. Chem. Chem. Phys., 2018, 20, 23564-23577. Figure 1

Mechanistic Exploration of Visible Light-Activated Carbon/TiO2 Hybrid Dots Damaging Bacterial Cells

The carbon/TiO2 hybrid dots (C/TiO2-Dots) are structurally TiO2 nanoparticles (in the order of 25 nm in diameter from commercially available colloidal TiO2 samples) surface-attached by nanoscale carbon domains with organic moieties, thus equivalent to hybrids of individual TiO2 nanoparticles each decorated with many carbon dots. These hybrid dots with exposure to visible light exhibit potent antibacterial properties, similar to those found in neat carbon dots with the same light activation. The results from the use of established scavengers for reactive oxygen species (ROS) to “quench” the antibacterial activities, an indication for shared mechanistic origins, are also similar. The findings in experiments on probing biological consequences of the antibacterial action suggest that the visible light-activated C/TiO2-Dots cause significant damage to the bacterial cell membrane, resulting in higher permeability, with the associated oxidative stress leading to lipid peroxidation, inhibiting bacterial growth. The induced bacterial cell damage could be observed more directly in the transmission electron microscopy (TEM) imaging. Opportunities for the further development of the hybrid dots platform for a variety of antibacterial applications are discussed.