TiO2 Surface Research Articles

Cyanide Removal by ZnTiO3/TiO2/H2O2/UVB System: A Theoretical-Experimental Approach.

Cyanide is a highly toxic substance present in wastewater from various industries. This study investigates the removal of cyanide species (CS) from aqueous solutions using the ZnTiO3/TiO2/H2O2/UVB system. ZnTiO3/TiO2 nanoparticles synthesized by the sol-gel method were characterized by powder X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The adsorption capacity of nanoparticles was tested by varying the pH of the solution, adsorbent concentration, and contact time. The adsorption of CS on ZnTiO3 and TiO2 surfaces was verified by Density Functional Theory (DFT) calculations. Photocatalytic experiments were achieved under UVB irradiation (λ = 310 nm). The response surface methodology (RSM) was used to optimize the CS removal efficiency. The detoxification effect was evaluated by acute toxicity tests with brine shrimp. The theoretical results show that the adsorption of CS is energetically more favorable on the ZnTiO3 surface than on the TiO2 surface. The experimental results show that the system consisting of ZnTiO3/TiO2 (200 mg L-1), H2O2 (0.1%), and UVB light removes 99% of CS from aqueous solutions after 60 min and reduces the mortality of nauplii in 90% after 90 min. This system was reused in five consecutive cycles with a total loss of efficiency of 30%.

Green synthesis of aryl‐(4‐oxo‐1,2‐dihydroquinazolin‐4‐yl‐methylene) pyrazole‐TiO2 nanoparticles as dyes removable for waste water treatment

Facile synthesis for true intermediate (E)‐ and Z‐2‐(((5‐bromo‐1‐(3‐chloropyridin‐2‐yl)‐1H‐pyrazol‐3‐yl)methylene)amino)‐5‐chloro‐3‐methylbenzoic acid precursors and 2‐(5‐bromo‐1‐(3‐chloropyridin‐2‐yl)‐1H‐pyrazol‐3‐yl)‐6‐chloro‐3,8‐dimethylquinazolin‐4(3H)‐one (QPP) as electron donor/electron acceptor to be working as efficient dye sensitizers. These new derivatives have a wide‐band gap photo‐catalysts semiconductor and are performing to spread to the visible‐light region to give more stability and efficiency towards biomedicine for different diseases. In the present work, the authors are suggesting the design and synthesis of new structures of QPP molecule with extended visible light absorptivity due to the extended π‐π/n‐π conjugations, to stimulate TiO2 nanoparticles in visible‐light region. The physicochemical characterizations confirmed the successful synthesis of QPP, TiO2, and QPP II/TiO2 samples with the proposed structures. Fixing of QPP on the TiO2 surface is refining the optical properties of TiO2 with enhancing the charge separation and generating the efficient antenna in the visible region. Furthermore, the QPP II/TiO2 sample achieved a threefold enhancement in the observed rate constant of the photo‐degradation of rhodamine B dye when compared to the bare TiO2. Finally, the effect of the scavengers was investigated by to be the most reactive species, and the mechanism of the enhancement was suggested for investigation of the proposed structures in various photo‐catalytic and biomedical applications.

Cu and Pd dual-single-atoms anchored titanium dioxide for remarkable photocatalytic H2 evolution efficiency

Metal single-atoms (SA) are considered as an effective cocatalyst in photocatalyst for their unsaturated coordination and distinguished activity. However, the precious metal single-atoms catalyst (SACs) approach the maximum activity limit, how to further improve the catalytic efficiency is challenging. In this work, an atomic-level photocatalyst was designed to use the synergy between Pd and Cu dual-SA constructed on TiO2 surface. The synthesized PdCu/TiO2 photocatalyst achieves ultrahigh and stable photocatalytic activity with H2 production of 94.35 mmol∙g−1∙h−1 by splitting water, which is 2.65 and 2.78 times to the PdSA/TiO2 and CuSA/TiO2, respectively, which also higher than most reported photocatalysts. Furthermore, the apparent quantum efficiency (AQE) reaches 83.81 % at 365 nm.Detailed investigations indicate that the outstanding activity of PdCu/TiO2 is mainly attributed to the Pd-O-Cu dimer-site formed in the photocatalyst, which can not only effectively facilitate the photoelectrons transfer to the active site and inhibit the recombination, but also balance the H* adsorption–desorption during the photocatalytic H2 evolution (PHE) process, thus greatly promoting the splitting water reaction. This work provides a new insight for developing bimetallic SACs with high PHE efficiency.

Theoretical study of new 3-(methylthio)-8-phenyl-8H-thieno[2,3-b]indole derivatives for application in DSSC: Solvent effect, adsorption process on the surface of TiO2

This investigation aims to elucidate the influence of chemical modifications of the π-bridge on the optoelectronic properties of a newly designed series of five dyes Di (i = 1–5). In this regard, the molecules are designed with 3-(methylthio)-8-phenyl-8H-thieno[2,3-b] indole as electron-donating fragments and cyanoacrylic acid as electron-accepting groups. To attain this goal, the optoelectronic properties of the Di dyes and the reference dye MKZ-39 were theoretically investigated in both the gas phase (GP) and Toluene solvent (TS) using Density Functional Theory (DFT). In addition, to predict the absorption spectrum and excited state properties of theoretical Di molecules, we have resorted to Time-dependent Density Functional theory (TD-DFT). Furthermore, the Monte Carlo approach was employed to theoretically evaluate the process of dye adsorption onto the surface of TiO2 (110) anatase to determine the most stable TiO2-dye-100 C7H8 complex. The results presented demonstrate that the selected dyes possess auspicious characteristics as potential promoters for solar cells, including a redshift of λMax that can reach 561 nm, a nearly complete Light-Harvesting Efficiency (LHE) of 99 %, and a higher open-circuit voltage (VOC) compared to the reference molecule. Our results could open new perspectives for further experimental research into the chemical-structural modifications of these sensitizers.

Free-Electron Inversive Modulation to Charge Antibonding Orbital of ReS2 Cocatalyst for Efficient Photocatalytic Hydrogen Generation.

The free electron transfer between cocatalyst and photocatalyst has a great effect on the bonding strength between the active site and adsorbed hydrogen atom (Hads), but there is still a lack of effective means to purposely manipulate the electron transfer in a beneficial direction of H adsorption/desorption activity. Herein, when ReSx cocatalyst is loaded on TiO2 surface, a spontaneous free-electron transfer from ReSx to TiO2 happens due to the smaller work function of ReSx, causing an over-strong S-Hads bond. To prevent the over-strong S-Hads bonds of ReSx in the ReSx/TiO2 , a free-electron reversal transfer strategy is developed to weaken the strong S-Hads bonds via increasing the work function of ReSx by incorporating O to produce ReOSx cocatalyst. Research results attest that a larger work function of ReOSx than that of TiO2 can induce reversal transfer of electrons from TiO2 to ReOSx to produce electron-rich S(2+δ)-, causing the increased antibonding-orbital occupancy of S-Hads in ReOSx/TiO2 . Accordingly, the stability of adsorbed H on S sites is availably decreased, thus weakening the S-Hads of ReOSx. In this case, an electron-rich S(2+δ)--mediated "capture-hybridization-conversion" mechanism is raised . Benefiting from such property, the resultant ReOSx/TiO2 photocatalyst exhibits a superior H2-evolution rate of 7168µmol h-1 g-1 .

Surface diffusion induced degradation enhancement and zero-order kinetics in edge-connected MoS2/Au/TiO2 Z-scheme photocatalytic system

Heterostructured photocatalysts have demonstrated great potential in the photodegradation of organic pollutants, while the surfaces & interfaces of their multiple structural components play critical roles in determining their photocatalytic mechanisms and kinetics. Here, we fabricate an edge-connected MoS2/Au/TiO2 photocatalytic system via a selective photodeposition method and utilize a surface-diffusion mechanism to maximize the synergistic effects among the components. The resultant photocatalytic system behaves as a Z-scheme with well spatially separated redox reaction sites. The optimal catalyst 10 % MS/Au/T exhibited a pseudo 1st-order rate constant of 0.0145 min−1 within 120 min, which is seven times more than that of pristine TiO2. The edge-deposited MoS2 in the nanocomposite serves as a reservoir to adsorb and then transport the pollutant molecules rapidly to TiO2 surface for oxidation. Such a pre-concentration effect, as well as the Z-scheme charge transfer mechanism, has enhanced the overall degradation efficiency, and induced the occurrence of zero-order degradation kinetics. The charge transfer behaviors, the diffusion-enhancement mechanism, zero-order kinetics, and the order transition are then thoroughly studied against the MoS2 mass loading. 10 % MS/Au/T showed the highest values of zero and first-order constants, which were 0.073 ppm/min and 0.011 min−1, respectively. A diffusion-enhanced model is developed and validated to explain the experimental observations. This work provides meaningful insights into degradation enhancement and kinetic analysis for heterostructured photocatalytic systems.

Thin alumina-coated polyoxometalates on gold-titania half-shell array photoanode for sustainable plasmonic water oxidation

In solar water splitting, the poor chemical and mechanical durability of photoanode materials under oxidative environments has been raised as a crucial issue. Despite promising water oxidation activity, the stable immobilization of polyoxometalates (POMs) onto photoanodes is very challenging. Here we report sustainable photoelectrochemical water oxidation through the deposition of catalytic POMs onto a plasmonic Au/TiO2 photoanode, followed by the atomic layer deposition of a thin Al2O3 layer. Vacuum deposition techniques were used with polystyrene nanospheres as sacrificial templates to fabricate an Au/TiO2 half-shell array as a photoanode with strong plasmonic absorption and excellent stability in aqueous media. The thin Al2O3 layer serves as a protective layer for [Co4(H2O)2(PW9O34)2]10- (Co4POMs) attached to Au/TiO2 half-shells functionalized with cysteamines. The Al2O3 layer increased the photocurrent and delayed current attenuation by preventing the dissociation of Co4POMs from the surface during the water oxidation. A thicker Al2O3 layer exhibited a higher protection effect but reduced the catalytic activity of Co4POMs in the early stage of water oxidation due to the limited exposure of Co4POMs to electrolytes. Furthermore, regardless of the POMs, the Al2O3 layer also passivated the TiO2 surface, improving electron transfer through the POMs/Au half-shell structure. This work suggests that the catalyst/plasmonic photoelectrode with a thin protection layer is a promising alternative to conventional semiconductor-based photoelectrodes for sustainable and efficient water oxidation.

Indirect daylight oxidative degradation of polyethylene microplastics by a bio-waste modified TiO2-based material

Microplastics are recognized as an emerging critical issue for the environment. Here an innovative chemical approach for the treatment of microplastics is proposed, based on an oxidative process that does not require any direct energy source (irradiation or heat). Linear low-density polyethylene (LLDPE) was selected as target commodity polymer, due to its widespread use, chemical inertness and inefficient recycling. This route is based on a hybrid material coupling titanium oxide with a bio-waste, rosin, mainly constituted by abietic acid, through a simple sol-gel synthesis procedure. The ligand-to-metal charge transfer complexes formed between rosin and Ti4+ allow the generation of reactive oxygen species without UV irradiation for its activation. In agreement with theorical calculations, superoxide radical ions are stabilized at ambient conditions on the surface of the hybrid TiO2. Consequently, an impressive degradation of LLDPE is observed after 1 month exposure in a batch configuration under indirect daylight, as evidenced by the products revealed by gas chromatography-mass spectrometry analysis and by chemical and structural modifications of the polymer surface. In a context of waste exploitation, this innovative and sustainable approach represents a promising cost-effective strategy for the oxidative degradation of microplastics, without producing any toxic by-products.

Selected I-III-VI2 Semiconductors: Synthesis, Properties and Applications in Photovoltaic Cells.

I-III-VI2 group quantum dots (QDs) have attracted high attention in photoelectronic conversion applications, especially for QD-sensitized solar cells (QDSSCs). This group of QDs has become the mainstream light-harvesting material in QDSSCs due to the ability to tune their electronic properties through size, shape, and composition and the ability to assemble the nanocrystals on the surface of TiO2. Moreover, these nanocrystals can be produced relatively easily via cost-effective solution-based synthetic methods and are composed of low-toxicity elements, which favors their integration into the market. This review describes the methods developed to prepare I-III-VI2 QDs (AgInS2 and CuInS2 were excluded) and control their optoelectronic properties to favor their integration into QDSSCs. Strategies developed to broaden the optoelectronic response and decrease the surface-defect states of QDs in order to promote the fast electron injection from QDs into TiO2 and achieve highly efficient QDSSCs will be described. Results show that heterostructures obtained after the sensitization of TiO2 with I-III-VI2 QDs could outperform those of other QDSSCs. The highest power-conversion efficiency (15.2%) was obtained for quinary Cu-In-Zn-Se-S QDs, along with a short-circuit density (JSC) of 26.30 mA·cm-2, an open-circuit voltage (VOC) of 802 mV and a fill factor (FF) of 71%.

Architecture design of TiO2 with Co-doped CdS quantum dots photoelectrode for water splitting.

Photoelectrochemical hydrogen production is a critical key to solving the carbon-zero goal of countries due to renewable sources of solar light and combustion products of hydrogen-only water. Here, an architecture design for an n-type nano rosettes-rod TiO2 (RT) surface using CdS and Co-doped CdS quantum dots (QDs) is carried out utilizing the SILAR (simple ionic layer adsorption and reaction) method. Furthermore, the photocatalytic behaviour of Co-doped CdS QDs SILAR cycles deposition is investigated in various cycles, including 5, 8, 10, and 12. The FESEM, Raman XRD, Uv-Vis spectrometer, and vibration modes are used to evaluate the photoelectrode surface structure, crystal structure, and solar light absorption, respectively. FESEM images and XRD pattern revealed successive CdS QDS and Co-doped CdS QDs deposition on the RT boundary and rising SILAR cycles of Co-doped CdS QDs lead to further coverage of RT surface. UV-vis spectrometer indicated shifting solar light absorption to the visible region by applying more SILAR cycles of Co-doped CdS QDs deposition. The electrochemical parameters obtained from EIS showed total polarization resistance (Rp) of the RT electrode dramatically decreased with 10 SILAR cycle Co-doped CdS QDs deposition (5093 Ω cm2 and 617 Ω cm2). Linear sweep voltammetry (LSV) and chronoamperometric photocatalytic performance measurements indicated Co-doped CdS QDs on RT extremely enhanced photoresponse under solar irradiation and 10 SILAR cycle Co-doped CdS QDs improved photocurrent density about fourfold according to blank RT electrode.

The effect of Ti-based surface layer on AlSi thin film as a high-performance anode for the lithium-ion battery

Significant volume changes during cycling and the instability of the solid electrolyte interphase (SEI) are the main challenges that limit the practical application of silicon-based anodes. TiN and TiO2 were selected as surface layers and deposited on the HCl-etched AlSi (AlSi’) thin films by atomic layer deposition (ALD) to enhance the electrochemical performance of the anode. The surface layers with excellent mechanical strength can effectively suppress the volume expansion of the AlSi thin film and maintain excellent electrical contact between the film and the substrate during cycling. The effects of TiN and TiO2 surface layers on the composition and growth of the SEI layer on the AlSi’ film anode have been discussed in detail. The TiO2 surface layer was found to inhibit the continuous growth of the SEI layer and promote the formation of a mechanically robust and stable SEI layer. The AlSi’/TiO2(8 nm) anode shows a high initial discharge capacity of 2802 mA h g-1 with an initial coulomb efficiency (ICE) of 88% at 0.8 A g-1, and it maintains a capacity retention rate of 83% after 500 cycles. Moreover, the AlSi’/TiO2(8 nm) anode exhibits outstanding rate performance, as it sustains a capacity of 1710 mA h g-1 after 500 cycles at 5 A g-1, and maintains a capacity above 1032 mA h g-1 even at 30 A g-1.

3D/2D photocatalyst fabricated from Pt loading TiO2 nanoparticles and converter slag-derived Fe-doped hydroxyapatite for efficient H2 evolution

H2 generation for partially substituting coke by the photocatalysts fabricated from steel slag presents a desirable approach to on-site carbon footprint reduction in the iron and steel-making industry, both environmentally and economically. However, achieving high photocatalytic H2 production activity is primarily limited by the scarcity of active sites due to a small specific surface area, inefficient charge transfer, and partly restricted by slow kinetics of the H2 generation reaction. In this study, 1 wt% Pt clusters are photo-reduced onto sub-15 nm TiO2 nanoparticles (TiO2-Pt) in 20 vol% methanol. Subsequently, the electrostatic assembling method has been employed to combine steel-making converter slag-derived Fe-doped hydroxyapatite (FeHAp) with TiO2-Pt, forming a type II 3D/2D TiO2-Pt/FeHAp heterojunction. Excellent connectivity between these two phases contributes to efficient charge separation, forming a built-in electric field that drives the photo-generated electrons to flow from FeHAp to the Pt cocatalyst on TiO2 nanoparticles through the type-II path. By the synergistic effects, including the large specific surface of sub-15 nm TiO2, Pt cocatalyst-offered rapid H2 generation kinetics,. and the heterostructure-provided enhancement of interfacial charge migration and separation, 60 mg TiO2-Pt/5FeHAp presents an enhanced H2 production activity in 120 mL of 10 vol% triethanolamine (TEOA), enabling the H2 generation rate (3026 μmol·g−1·h−1) to reach 1.85 and 75.78 times greater than that of pristine TiO2-Pt (1638 μmol·g−1·h−1) and FeHAp-Pt (40 μmol·g−1·h−1), respectively, under UV–visible light irradiation for 3 h at 8 °C and obtaining an apparent quantum yield of 4.72 % at 370 nm. This study provides a promising strategy for green hydrogen-based steel-making in the sustainable development of the steel industry.

Structure and optical properties of polyaniline-based hybrid nanocomposites by chemical oxidative method

Titanium - polyaniline nanocomposites were prepared using polymerization of aniline. Structure (XRD), surface (SEM, AFM), chemical (FTIR) and optical (UVSpectrophotometer) properties have been examined. The X-ray diffraction pattern observed the PANI/TiO2 has a crystalline nature and the peak intensity increases with TiO2 composition ratio, the results of SEM &AFM images show the surface of TiO2- polyaniline have regular distribution and homogeneous structure. Furthermore, the grain size increases with increasing of TiO2 compositions and was found to be 32.58nm, 36.21nm and 47.67 nm at x= 0.2, 0.5 and 0.8 respectively. Additionally, optical properties show that the absorption intensity increases with TiO2 compositions compared to pure TiO2. Hybrid of TiO2/PANI has a vast attracted attention especially to improve photocatalytic activity. Simple design and high quality of nanocomposites play a crucial role in improving mechanical and physical properties.

Evaluation of chitosan-Ag/TiO2 nanocomposite for the enhancement of shelf life of chili and banana fruits

Post-harvest losses of fruits and vegetables account for a large share of food waste in the world due to improper handling and packaging. By using the sol-gel method, Ag/TiO2 nanocomposite was prepared in this study from micro-sized commercial TiO2 powder and incorporated in a chitosan-cellulose matrix for the purpose of promising food packaging. The particle size and distribution of Ag nanoparticles (9.2437 nm size) confirmed their successful inclusion in the TiO2 surface. The morphology of the package assured the successful and uniform disbursement of Ag/TiO2 nanocomposite into the chitosan-cellulose matrix, which led to enhanced water resistance and photocatalytic activity. The developed package is proficient in hindering the growth of fecal coliform bacteria (Esche (Escherichia coli) by 9 mm in the agar plate. Moreover, the efficient application of chitosan-Ag/TiO2 nanocomposite in food coating and packaging was examined in extending shelf life, minimizing water loss, and preventing microbial infection during the storage of chili (up to 7 days at 37 °C) and banana, respectively. It can be concluded from the results that chitosan-Ag/TiO2 nanocomposite-based food coating and packaging have competent potential for enhancing the shelf life of moist foods.

XPS and HR TEM Elucidation of the Diversity of Titania-Supported Single-Site Ir Catalyst Performance in Spin-Selective Propene Hydrogenation

Immobilized [Ir(COD)Cl]2-Linker/TiO2 catalysts with linkers containing Py, P(Ph)2 and N(CH3)2 functional groups were prepared. The catalysts were tested via propene hydrogenation with parahydrogen in a temperature range from 40 °C to 120 °C which was monitored via NMR. The catalytic behavior of [Ir(COD)Cl]2-Linker/TiO2 is explained on the basis of quantitative and qualitative XPS data analysis performed for the catalysts before and after the reaction at 120 °C. It is shown that the temperature dependence of propene conversion and the enhancement of the NMR signal are explained via a combination of the stabilities of both the linker and immobilized [Ir(COD)Cl]2 complex. It is demonstrated that the N(CH3)2-linker is the most stable at the surface of TiO2 under used reaction conditions. As a result, only this sample shows a rise in the enhancement of the NMR signal in the 100–120 °C temperature range.

Bifunctional TiO2−x nanofibers enhanced gel polymer electrolyte for high performance lithium metal batteries

Exploration of advanced gel polymer electrolytes (GPEs) represents a viable strategy for mitigating dendritic lithium (Li) growth, which is crucial in ensuring the safe operation of high energy density Li metal batteries (LMBs). Despite this, the application of GPEs is still hindered by inadequate ionic conductivity, low Li+ transference number, and subpar physicochemical properties. Herein, TiO2−x nanofibers (NF) with oxygen vacancy defects were synthesized by a one-step process as inorganic fillers to enhance the thermal/mechanical/ionic-transportation performances of composite GPEs. Various characterizations and theoretical calculations reveal that the oxygen vacancies on the surface of TiO2−x NF accelerate the dissociation of LiPF6, promote the rapid transfer of free Li+, and influence the formation of LiF-enriched solid electrolyte interphase. Consequently, the composite GPEs demonstrate enhanced ionic conductivity (1.90 mS cm−1 at room temperature), higher lithium-ion transference number (0.70), wider electrochemical stability window (5.50 V), superior mechanical strength, excellent thermal stability (210 °C), and improved compatibility with lithium, resulting in superior cycling stability and rate performance in both Li||Li, Li||LiFePO4, and Li||LiNi0.8Co0.1Mn0.1O2 cells. Overall, the synergistic influence of nanofiber morphology and enriched oxygen vacancy structure of fillers on electrochemical properties of composite GPEs is comprehensively investigated, thus, it is anticipated to shed new light on designing high-performance GPEs LMBs.

Self-assembly, structure and catalytic activity of Ni3 on TiO2: A triple-atom catalyst for hydrogen evolution

Triple-atom catalysts (TACs), structurally derived from single-atom catalysts (SACs) but beyond SACs in the active sites, have received increasing attention but are still in their infant stage. Using density functional theory, we study the self-assembly of the Ni3 trimer on TiO2 (Ni3/TiO2) by atom-by-atom deposition. Coordinatively unsaturated sites on the TiO2 surface are responsible for this self-assembly, resulting in different configurations of Ni3. According to the orientation relationship and lattice mismatch, an embryo of Ni crystal is thought to be born of triangle Ni3 trimer on TiO2. The hydrogen evolution reaction activity and mechanism of Ni3/TiO2 with different H coverages are evaluated using thermochemistry and kinetics calculations. Only at high H coverage would Ni3/TiO2 TACs exhibit a hydrogen production activity higher than that of Ni1/TiO2 SACs, indicating the matching relationship between multiple active sites and multi-step reaction intermediates for the active-site utilization. The quantum confinement effect throughout Nin/TiO2 (n = 1–3) is evidenced by the localization of metallic states of Nin. Our results not only open the possibility for synthesizing multimers on oxides by self-assembly, but also enrich the quantum control toolbox in few-atom catalysts by coordination modulation.

Density functional theory study the mechanism of two CO* forming *OC-CO on different size of Cun (n = 3 to 20) clusters supported on TiO2

Cun@TiO2 nanocatalytic materials are widely used in experiments to catalyze the reduction of CO2 to hydrocarbon fuels and oxygenated alcohols. However, due to the complexity of the coupling reaction of the Cun@TiO2 catalyst to form key CC bonds to C2 products, it is unclear. In this paper, the density functional theory (DFT) is employed to systematically study the influence of the size of Cun clusters on the CC bond formation with the Cun cluster supporting on the TiO2 surface. It was discovered that the adsorption of Cu metal clusters of different sizes on TiO2 was primarily determined by the bonding of TiO2 oxygen atoms. Subsequently, in the CO*+CO* → COOC* coupling reaction on each different Cun cluster size, we found that the active site was the interface position, when the Cun cluster showed a three-dimensional configuration, with the increase of the Cu cluster, that is, the coordination number increased, the activation energy barrier gradually decreased, and when the coordination of Cu cluster reached saturation, the coupling energy barrier size also stabilized. This work provides new sight of the size of co-catalyst in the CO2 reduction reaction and may guide to synthesis higher efficiency co-catalyst.

Growth of Dichalcogenide Layers on TiO2(110)—MoSe2 or TiSe2

Transition‐metal dichalcogenide (TMDC) islands and thin films are grown on TiO2(110) via physical vapor deposition of Mo and Se and are analyzed with electron diffraction, Auger spectroscopy, and scanning tunneling microscopy (STM). Surprisingly, large, crystalline TiSe2 patches develop on the TiO2 surface instead of the expected MoSe2 islands. They are identified by a hexagonal lattice with 3.4 Å periodicity, a unique (2 × 2) superstructure related to charge‐density waves, and an empty conductance doublet in STM spectroscopy. Density‐function‐theory calculations assign the imaging contrast and the conductance doublet to tunneling into the 3p orbitals of the topmost Se layer and Ti 3d‐related electronic states, respectively. Control experiments without Mo deposition confirm that the observed TMDC growth indeed results from a surface reaction between gas‐phase Se and Ti3+ atoms, segregating out of the reduced TiO2 crystal. From the unique shape and orientation of the TiSe2 islands in the low‐coverage regime, a distinct nucleation scheme is proposed, in which the Se(3 × 1) superstructure on TiO2 provides pinning centers for the TMDC. This article aims at increasing the awareness that Mo and Se co‐deposition does not automatically result in MoSe2 formation, but parasitic processes may trigger the growth of other TMDCs.

Controlling molecular self-assembly of inverse-phosphocholine lipids at oxide interfaces with divalent cations

Sub-100 nm vesicles composed of inverse-phosphocholine (CP) lipids are versatile building blocks for interfacing with inorganic material surfaces and demonstrate unique chemical functionalities due to outward-facing phosphate groups. Compared to typical phospholipids, the surface presentation of CP lipids has enabled new covalent possibilities like click chemistry for drug delivery and imaging applications while utilizing this phosphate chemistry in noncovalent self-assembly contexts remains unexplored. Herein, we report that the presence of phosphate-binding divalent cations such as Ca2+ and Mg2+ can dramatically shift the self-assembly behavior of CP lipid vesicles on TiO2 and SiO2 surfaces, inhibiting spontaneous supported lipid bilayer (SLB) formation on TiO2 in cases where it typically occurs and promoting SLB formation on SiO2 in cases where lipid adsorption is otherwise negligible. Quartz crystal microbalance-dissipation (QCM-D) measurements were performed to track the corresponding adsorption kinetics and self-assembly outcomes. Importantly, an optimal combination of CP lipid fraction in vesicles and specific divalent cation type was also identified, which enabled SLB formation on both TiO2 and SiO2 surfaces under equivalent conditions. SLB fluidity on SiO2 surfaces was additionally confirmed by fluorescence recovery after photobleaching (FRAP) experiments. We rationalize these molecular-level phenomena in terms of vesicle stability and lipid-surface interactions, demonstrating a versatile approach to control CP lipid self-assembly with divalent cations.