Anatase Surface Research Articles

Combined Role of {001} Facet-Enriched Morphology and Gold Nanoparticle Deposition on Anatase TiO2 Photoactivity.

The interplay on anatase TiO2 photoactivity between particle morphology and gold nanoparticles (NPs) deposition, via either deposition-precipitation (DP) or photodeposition (P), is here investigated by evaluating the photoactivity of Au modified anatase (Au/TiO2) nanocrystals with either a pseudospherical shape or a nanosheet structure in both reduction and oxidation test reactions. The presence of Au NPs on the anatase surface only slightly affects its photoactivity in Cr(VI) reduction, which is kinetically limited by the anodic half-reaction, whereas a larger exposure of highly oxidant {001} facets is beneficial for overcoming this rate-determining step. In the photocatalytic oxidation of both formic acid, proceeding through a direct mechanism, and rhodamine B (RhB) on surface fluorinated photocatalysts, occurring through a hydroxyl-radical-mediated mechanism, the presence of gold NPs produces a significant photoactivity increase only with spherically shaped photocatalysts, mainly exposing {101} facets. These results are rationalized in light of the preferential migration of photogenerated, oppositely charged carriers toward different crystal facets. In fact, when the Au/TiO2 material mainly exposes the more oxidant {001} facets, where photoproduced holes preferentially migrate, recombination between these latter and the electrons captured by Au NPs is favored. Instead, Au NPs on {101} facets efficiently capture photopromoted electrons, preferentially migrating toward such facets with a consequent improvement of photoproduced charge separation.

Icelike water molecules with single hydrogen bond donor on the surface of nano anatase and rutile particles by IR spectroscopy

The hydration behavior of TiO2 nanoparticles was studied by molecular dynamics simulations and a novel IR ratio spectroscopy method. It was found that the hydration water at the titanium dioxide interface contains molecules with a large number of single hydrogen bond donors, and approximately five water layers were confined within the nano-grooves of the nanoparticles. The confinement effect was observed to enhance the strength of the hydrogen bonds and to slow down the movement of the water molecules around the surface of the nanoparticles.

Acoustic Shock Wave-Induced Rutile to Anatase Phase Transition of TiO2 Nanoparticles and Exploration of Their Unconventional Thermodynamic Structural Transition Path of Crystallization Behaviors.

Titanium dioxide (TiO2) is one of the most well-known and long-standing polymorphic materials in the transition metal oxide group of materials. The transition from rutile to anatase is one of the long-standing fundamental questions among materials science researchers because seeking the nucleation site at the beginning of the phase transition is highly challenging. Until now, there have been no studies on the unconventional structural phase transition of TiO2 nanoparticles by acoustic shock waves. In the present study, this work provides the first evidence on the solid-state nanostructure of the rutile-to-anatase phase transition of TiO2 by acoustic shock waves whereby these phase transition results are evaluated by Raman spectroscopy, thermal calorimetry, X-ray photoelectron spectroscopy, and microscopic techniques. We propose a novel mechanism for the occurrence of the rutile-to-anatase phase transition based on thermophysical properties and shock wave-induced melting concepts. Under shocked conditions, the R-A phase transition occurs because of the anatase phase's lower interfacial energy (γL/A) and surface energy compared to rutile. We strongly believe that the present work can provide in-depth insight into understanding the crystallization concepts of the TiO2 NPs under extreme conditions, especially with regard to the rutile-to-anatase phase transition.

Ultrasonic-Induced Surface Disordering Promotes Photocatalytic Hydrogen Evolution of TiO2.

Surface disordering has been considered an effective strategy for tailoring the charge separation and surface chemistry of semiconductor photocatalysts. A simple but reliable method to create surface disordering is, therefore, urgently needed for the development of high-performance semiconductor photocatalysts and their practical applications. Herein, we report that the ultrasonic processing, which is commonly employed in the dispersion of photocatalysts, can induce the surface disordering of TiO2 and significantly promote its performance for photocatalytic hydrogen evolution. A 40 min ultrasonic treatment of TiO2 (Degussa P25) enhances the photocatalytic hydrogen production by 42.7 times, achieving a hydrogen evolution rate of 1425.4 μmol g-1 h-1 without any cocatalyst. Comprehensive structural, spectral, and electrochemical analyses reveal that the ultrasonic treatment induces the surface disordering of TiO2, and consequently reduces the density of deep electron traps, extends the separation of photogenerated charges, and facilitates the hydrogen evolution reaction relative to oxygen reduction. The ultrasonic treatment manifests a more pronounced effect on disordering the surface of anatase than rutile, agreeing well with the enhanced photocatalysis of anatase rather than rutile. This study demonstrates that ultrasonic-induced surface disordering could be an effective strategy for the activation of photocatalysts and might hold significant implications for the applications in photocatalytic hydrogen evolution, small molecule activation, and biomass conversion.

Modeling adsorption reactions of ammonium perchlorate on rutile and anatase surfaces.

In this work, the effects of two TiO2 polymorphs on the decomposition of ammonium perchlorate (NH4ClO4) were studied experimentally and theoretically. The interactions between AP and various surfaces of TiO2 were modeled using density functional theory (DFT) calculations. Specifically, the adsorption of AP on three rutile surfaces (1 1 0), (1 0 0), and (0 0 1), as well as two anatase surfaces (1 0 1), and (0 0 1) were modeled using cluster models, along with the decomposition of adsorbed AP into small molecules. The optimized complexes of the AP molecule on TiO2 surfaces were very stable, indicating strong covalent and hydrogen bonding interactions, leading to highly energetic adsorption reactions. The calculated energy of adsorption (ΔEads) ranged from -120.23 to -301.98 kJ/mol, with highly exergonic calculated Gibbs free energy (ΔGads) of reaction, and highly exothermic enthalpy of reaction (ΔHads). The decomposition of adsorbed AP was also found to have very negative ΔEdec values between -199.08 and -380.73 kJ/mol. The values of ΔGdec and ΔHdec reveal exergonic and exothermic reactions. The adsorption of AP on TiO2 surfaces anticipates the heat release of decomposition, in agreement with experimental results. The most common anatase surface, (1 0 1), was predicted to be more reactive for AP decomposition than the most stable rutile surface, (1 1 0), which was confirmed by experiments. DFT calculations show the mechanism for activation of the two TiO2 polymorphs is entropy driven.

Catalytic mechanisms for As(III) oxidation by H2O2 over TiO2 surfaces, and effects of support, vacancy and photoirradiation

As(III) is much more toxic than As(V) while shows apparently lower affinity at minerals surfaces. Oxidation of As(III) to As(V) by H2O2 over anatase surface provides an attractive avenue for pollution control, and the chemocatalytic and photocatalytic mechanisms are unraveled by means of the DFT + D3 approach. Impacts of anatase as support, O2c/O3c vacancy, photoirradiation are addressed as well. As(III) oxidation under various reaction conditions leads to As(V) through dual electron transfers, while energy barriers differ substantially and decline as 1.80 (direct oxidation) > 1.35 (anatase as support) > 1.24 (O3c vacancy) > 0.50 (chemocatalysis) > 0.28 (photocatalysis) ≥ 0.26 (O2c vacancy) eV. Anatase as support promotes the reaction through bonding with H2O2/As(OH)3 and electron transfers, and its close participation during chemocatalysis produces the TiOOH active site that causes As(III) oxidation to proceed facilely under ambient circumstances. TiOOH exists in two forms (monodentate and bidentate mononuclear) and is critical for chemocatalysis, while its destruction for O3c vacancy exhibits strongly adverse effects to As(III) oxidation. Photoirradiation readily generates the OH• radicals, and corresponding mechanism is plausible while less preferred than the newly posed mechanism based on the Ti(H2O2) active site. Synergism among a number of surface atoms conduces to the superior activity for O2c vacancy and photocatalysis. Results provide a comprehensive understanding for As(III) oxidation to As(V) by H2O2, and facilitate catalysts design for As(III) oxidation that alleviates environmental pollution.

Wettability of anatase TiO2 surface: Effect of niobium doping

The effect of niobium doping on the hydrophilic behavior of anatase TiO2 surface was demonstrated on a series of x-Nb-TiO2 nanocoatings with dopant concentrations in the range of 0.0 - 1.0 at.% Nb. Thin films prepared on glass substrates from sols by dip-coating were characterized by tensiometric, work function and isoelectric point measurements along with FT-IR spectroscopy in situ method. Using macroscopic and microscopic techniques, it was found that, at low doping level, it is the functionalization of the anatase surface with niobium ions that leads to a drastic change in its surface acid-base as well as electronic properties and, as a consequence, to a sharp increase in the initial surface hydrophilicity. The rearrangement in the hydroxyl‑hydrated layer with the formation of additional hydroxyl groups as a result of surface functionalization has an increased effect on wettability only at low levels of niobium inclusion, whereas with increasing dopant content the electronic factor plays a significant role on the properties of titanium dioxide, including its wettability. The kinetic dependencies of the photoinduced superhydrophilic conversion for all Nb-doped titanium dioxide surfaces were obtained and discussed in terms of proposed mechanism. Both the initial hydrophilic state and the initial rate of photoinduced hydrophilic conversion depend on the Nb concentration in titanium dioxide, while the final UV-induced superhydrophilic state is achieved for all Nb-doped TiO2 regardless of the dopant content.

Nature of TiO2–oligonucleotides interactions by atomistic molecular dynamics simulations

We used molecular dynamics simulations to investigate the adsorption behavior of single-stranded deoxyribonucleic acid (ssDNA) segments on the anatase (101) surface. Four different ssDNA oligonucleotides, each consisting of six/twelve adenine (A6 and A12), six guanine (G6), six cytosine (C6) or six/twelve thymine (T6 and T12) nucleobases, were considered. We observed that the initial interaction between the ssDNA and the surface occurs primarily through hydrogen bonding between the nucleobases and the surface, followed by strong chemical bonding between the terminal phosphate group and the anatase surface. The interactions between the nucleobases and the surface varied between the different ssDNA segments. Adenine showed the highest affinity for the surface, whereas thymine showed the lowest affinity. In addition, the purine bases interact more strongly when the surface is negatively charged (as it would be at physiological pH) than in neutral surface (slightly acidic conditions), in agreement with experimental data from fluorescence experiments and ATR-FTIR spectroscopy. Moreover, our study provides mechanistic insights into the dynamic behavior of ssDNA on the anatase surface and comparative analyses on how different conditions (pH, fragment length, composition, etc.) affect DNA/TiO2 interactions. Therefore, we expect that experimental scientists will benefit from our work in the design of optimal nanoconjugates for their specific final goals and applications.

A Perspective on the Investigation of Spectroscopy and Kinetics of Complex Molecular Systems with Semiclassical Approaches.

In this Perspective we show that semiclassical methods provide a rigorous hierarchical way to study the vibrational spectroscopy and kinetics of complex molecular systems. The time averaged approach to spectroscopy and the semiclassical transition state theory for kinetics, which have been first adopted and then further developed in our group, provide accurate quantum results on rigorous physical grounds and can be applied even when dealing with a large number of degrees of freedom. In spectroscopy, the multiple coherent, divide-and-conquer, and adiabatically switched semiclassical approaches have practically permitted overcoming issues related to the convergence of results. In this Perspective we demonstrate the possibility of studying the semiclassical vibrational spectroscopy of a molecule adsorbed on an anatase (101) surface, a system made of 51 atoms. In kinetics, the semiclassical transition state theory is able to account for anharmonicity and the coupling between the reactive and bound modes. Our group has developed this technique for practical applications involving the study of phenomena like kinetic isotope effect, heavy atom tunneling, and elusive conformer lifetimes. Here, we show that our multidimensional anharmonic quantum approach is able to tackle on-the-fly the thermal kinetic rate constant of a 135 degree-of-freedom system. Overall, semiclassical methods open up the possibility to describe at the quantum mechanical level systems characterized by hundreds of degrees of freedom leading to the accurate spectroscopic and kinetic description of biomolecules and complex molecular systems.

Effect of water on formic acid and formaldehyde decomposition on the TiO2 (110) surface

The catalytic and photocatalytic performance of TiO2 in air pollutant degradation is significantly influenced by the adsorption of water. Here, we explore the molecular mechanism of formic acid and formaldehyde decomposition and their interaction with water on the TiO2 (110) surface, employing density functional theory (DFT) calculations and reactive molecular dynamics (RMD) simulations. RMD simulations indicate that due to the competitive adsorption of water at the surface Ti site, formic acid predominantly exists in a monodentate dissociative adsorption form on the TiO2 (110) surface. Moreover, on the TiO2 (110) surface, water molecules inhibit the adsorption and dissociation of formic acid, but they facilitate that of formaldehyde, forming methanediol (*CH2OHO) and dioxymethylene (*CH2O2). DFT calculations suggest that the formation pathway of *CH2OHO or *CH2O2 is energetically favorable, but the formation of formate is difficult. This contrasts with the adsorption of formaldehyde on the anatase surface, where formate species are formed.

Structure of vanadia-titania catalysts doped with alkali metals according to solid-state NMR, ESR spectroscopies and DFT

In this work, V/M/TiO2 catalysts (M = Li, Na, K, Rb and Cs) were investigated with Solid-state nuclear magnetic resonance (SSNMR), electron paramagnetic resonance (ESR) and first-principles calculations. The total vanadium content corresponds to half monolayer (4 V atoms·nm−2 of TiO2 support surface), with V/M atomic ratio being 4/0.6. Static 51V and MAS 1H, 7Li, 51V, 23Na, 133Cs NMR spectra were acquired. Surface moieties of vanadium oxide on (001) anatase surface were modeled using density functional theory (DFT); their 51V NMR parameters were calculated with the Gauge-Including Projected Augmented Wave (GIPAW) method and compared to experimental data obtained with 51V SSNMR spectroscopy. It was found that mainly strongly bound vanadium sites (V3) are formed on anatase samples, located on TiO2 terminal oxygen atoms. Weakly bound vanadium sites (V1, V2) are formed on bridged anatase oxygen atoms. Supported alkali metals (Li, Na, K, Rb and Cs) on TiO2 were found to interact with protons located on the terminal and bridged TiO2 oxygen atoms. The relative ratio of weakly bound vanadium sites (V1, V2) increased on alkali-containing samples. Calculations performed showed lithium cation to prefer V-O-Ti or V-O-V bonds over VO, unsystematically deshielding vanadium nuclei. The presence of V3+ is likely to cause a loss of intensity in 51V NMR spectra.

Enhanced As(OH)3 adsorption by anatase TiO2 through facet control and Fe, N dual doping: A DFT+D3 study

Anatase and rutile, two major polymorphs of TiO2, have been used widely for environmental remediation, while anatase is apparently less effective for As(III) pollution management and needs substantial improvement. Herein, DFT calculations show that (001) rather than (101) and (100) facets of anatase are highly selective for As(III) adsorption. Facet control plays critical role during As(III) adsorption over pristine anatase surfaces and remains for mono doping, while diminishes substantially for dual doping. The second doping profoundly enhances As(III) adsorption for anatase facets with low activities and proves to be a viable strategy. Distinct from pristine surfaces where bidentate binuclear complexes prevail, monodentate complexes may become preferred due to doping, especially for dual doping where Fe site promotes adsorption via electronic effects. Doping causes As(III) oxidation when As centers interact directly with surfaces, and for mono doping, electron back-donation re-reduces As(V) to As(IV), while As(IV) occurs less for dual doping due to electron reservoir of Fe site that inhibits As(V) re-reduction. Regulatory mechanisms of facet control and effects of mono and dual doping for As(III) adsorption are further unraveled at molecular level. Results provide significant new insights for As(III) pollution management, and conduce to design As(III) scavengers and manage As-associated pollution.

A systematic DFT study of structure and electronic properties of titanium dioxide.

DFT functionals are of paramount importance for an accurate electronic and structural description of transition metal systems. In this work, a systematic analysis using some well-known and commonly used DFT functionals is performed. A comparison of the structural and energetic parameters calculated with the available experimental data is made in order to find the adequate functional for an accurate description of the TiO2 bulk and surface of both anatase and rutile structures. In the absence of experimental data on the surface energy, the theoretical predictions obtained using the high-accuracy HSE06 functional were used as a reference to compare against the surface energy values calculated with the other DFT functionals. A clear improvement in the electronic description of both anatase and rutile was observed by introducing the Hubbard U correction term to PBE, PW91, and OptPBE functionals. The OptPBE-U4 functional was found to offer a good compromise between accurately describing the structural and electronic properties of titania.

Electronic and Structural Properties of Antibacterial Ag–Ti-Based Surfaces: An Ab Initio Theoretical Study

Coatings with tunable multifunctional features are important for several technological applications. Ti-based materials have been used in diverse applications ranging from metallic diodes in electronic devices up to medical implants. This work uses ab initio calculations to achieve a more fundamental understanding of the structural and electronic properties of β-TiNb and its passive TiO2 film surfaces upon Ag addition, investigating the alterations in the electronic band gap and the stability of the antibacterial coating. We find that Ag’s 4d electrons introduce localized electron states, characterized by bonding features with the favoured Ti first neighbour atoms, approximately −5 eV below the fermi level in both β-TiNb bulk and surface. Ag’s binding energy on β-TiNb(110) depends on the local environment (the lattice site and the type of bonded surface atoms) ranging from −2.70 eV up to −4.21 eV for the adatom on a four-fold Ti site, offering a variety of options for the design of a stable coating or for Ag ion release. In Ti–O terminated anatase and rutile (001) surfaces, surface states are introduced altering the TiO2 band gap. Silver is bonded more strongly, and therefore creates a more stable antibacterial coat on rutile than on anatase. In addition, the Ag coating exhibits enhanced 4d electron states at the highest occupied state on anatase (001),which are extended from −5 eV up to the Fermi level on rutile (001), which might be altered depending on the coat structural features, thus creating systems with tunable electronic band gap that can be used for the design of thin film semiconductors.

The hydrophilicity mechanism of anatase and rutile (110) TiO2 films based on donor-acceptor complexes

When the surface of TiO2 is exposed to ultraviolet (UV) light, its hydrophilicity increases initially and then contact angle relaxation progresses over time. We investigated the source mechanism and working principles of long-lasting hydrophilicity in an ambient environment. Previously, we reported that the amount of donor-acceptor complexes (DACs) generated by polarizable OH groups with strong charge polarity is critical for maintaining long-lasting hydrophilicity (>90 days) on an anatase surface. In less reactive TiO2 films with low surface energy, a fast relaxation occurs due to the loss of polarizable OH groups. In this research, quantitative four-peak X-ray photoelectron spectroscopy analysis with TiO2 O 1 s spectra surface analysis was used to determine the relative amount of DACs and the binding energy shifting of water adsorbates on single crystal rutile (110) and polycrystalline anatase after UV exposure or plasma treatment. Films treated with oxygen or argon plasma and/or UV were analyzed and compared to suggested mechanisms that can occur on the surface of the TiO2 phase. All treated rutile (110) films except those treated with an Ar plasma exhibited rapid contact angle relaxation during the first 3 days, and the angle increased gradually to >50° over 14 days. In contrast, all anatase films retained long-lasting hydrophilicity, demonstrating a <∼10° contact angle over 56 days. At the first measurement, the binding energies were shifted for rutile (110) treated with O2 plasma and O2 plasma+UV films, demonstrating Ti–OH and DAC values of +0.15 eV each. However, the Ti–OH and DACs of all anatase films were located in the negative binding energy position, indicating that the DACs of rutile (110) were unstable due to a relatively weak bonding. In addition, the IOH/Ibulk intensity ratio of Ti–OH for rutile (110) treated with an O2 plasma increased significantly from 20 % to 37 %. However, the intensity ratio for O2 plasma+UV increased only from 20 % to 23.8 %. This result in combination with the binding energy shifting tendency indicates that relaxed OH groups increased rapidly without UV treatment. When rutile (110) was irradiated with UV, the effect of photoinduced electron-hole pairs shown with Ti 2p spectra was much shorter than that of anatase. Differences in relaxation occurred in both phases due to the charge polarity effect between rutile (110) and anatase, the unstable DACs related to weak OH groups, and the difference in surface characteristics. Using single crystal rutile (110) with a well-defined surface, these experiments validated further the DAC mechanism and theory presented by our group. Specifically, we confirmed that both the amount of DACs and the binding energy position shifting are important for long-term hydrophilicity.

Silver doped anatase nanocomposite: a novel photocatalyst with advanced activity under visible light for waste-water treatment

Anatase is a universal semiconductor photocatalyst; however, its wide band-gap energy limits its entire solar spectrum absorption to only 5%. Anatase could be activated in the visible region via nobel metal deposition. This study reports on the facile synthesis of colloidal mono-dispersed anatase nanoparticles of 5 nm particle size via hydrothermal synthesis. Nobel metals (Silver, Nickel) were deposited on colloidal anatase surface. The photocatalytic activities of Ag–TiO2, and Ni–TiO2 were investigated for the degradation of basic fuchsin dye. Ag–TiO2 nanocomposite demonstrated enhanced adsorption activity in dark, as well as superior photocatalytic. Ag–TiO2 nanocomposite demonstrated enhanced removal efficiency by 70.8% under visible irradiation to virgin anatase. Ag–TiO2 nanocomposite demonstrated enhanced oxygen-lattice with low binding energy using XPS analysis. Ag–TiO2 experienced band gap energy of 2.35 eV compared with 3.2 eV for virgin anatase; this feature could secure enhanced solar absorption. Ag–TiO2 demonstrated excellent photo-degradation efficiency of 88% with 0.3% H2O2 under visible light. Deposited silver could catalyze H2O2 decomposition and could promote free radical generation; Ag–TiO2 nanocomposite is a promising photocatalyst for wastewater treatment applications.

Quantum-chemical calculations of thermodynamic characteristics of some heterogeneous catalytic processes with the use of multilayer cluster models

The approaches to estimating the changes in enthalpy, entropy, and Gibbs energy of adsorption processes and heterogeneous catalytic reactions on the basis of the quantum chemical calculation data were studied. By comparing with the experimental data on CO adsorption on the anatase (TiO2) surface, the applicability of the developed multilayer cluster model for calculation of the adsorption energy (enthalpy) was shown. The data on the calculation methods of the entropy change in heterogeneous processes were analyzed. The use of the theories of an ideal two-dimensional gas and an ideal two-dimensional lattice gas for estimating a configuration contribution to the entropy of a heterogeneous process was studied. The density of adsorption centers on the (101) anatase surface and the population corresponding to the standard state of an ideal two-dimensional gas were calculated. The consistency of the studied models at low populations was shown, and the limits of their applicability were established.

Impact of Copper(II)-Imidazole Complex Modification on Polycrystalline TiO2: Insights into Formation, Characterization, and Photocatalytic Performance

Micrometer-sized polycrystalline anatase particles are widely used in materials and life sciences, serving as essential components in photocatalytic materials. The ability to tailor their composition, shape, morphology, and functionality holds significant importance. In this study, we identified and examined the non-destructive route of Copper(II) implantation at the surface of polycrystalline TiO2. The [Cu(en)(Im)2]2+ complex ion demonstrated a remarkable affinity to concentrate and bind with the semiconductor’s surface, such as anatase, forming a surface-bound adduct: ≡TiO2 + [Cu(en)(Im)2]2+ → ≡TiO2//[Cu(en)(Im)2]2+. The misalignment of Fermi levels in TiO2//[Cu(en)(Im)2]2+ triggered electron transfer, leading to the reduction of the metal center, releasing Copper(I) in the process. Although less efficient, the released Copper(I) encountered a highly favorable environment, resulting in the formation of the surface complex TiO2:CuIIsc. The implanted Cu(I) was converted back into Cu(II) due to re-oxidation by dissolved oxygen. The penetration of the metal ion into the surface level of the polycrystalline TiO2 lattice was influenced by surface residual forces, making surface grafting of the Cu(II) ion inevitable due to surface chemistry. FTIR, UV–vis, Raman, XRD, EPR, and surface morphological (SEM, EDAX, and HRTEM) analyses identified the typical surface grafting of the Cu(II) cluster complex on the anatase surface matrix. Moreover, the XRD results also showed the formation of an impure phase. The TiO2 polycrystalline materials, modified by the incorporation of copper complexes, demonstrated an enhanced visible-light photocatalytic capability in the degradation of Rhodamine B dye in aqueous solutions. This modification significantly improved the efficiency of the photocatalytic process, expanding the applicability of TiO2 to visible light wavelengths. These studies open up the possibility of using copper complexes grafted on metal oxide surfaces for visible-light active photocatalytic applications. Moreover, this investigation not only showcases the improved visible-light photocatalytic behavior of copper-modified TiO2 polycrystalline materials, but also underscores the broader implications of this improvement in the advancement of sustainable and efficient water treatment technologies.

Surface-Mediated Modulation of Different Biological Responses on Anatase-Coated Titanium.

Various surface modification strategies are being developed to endow dental titanium implant surfaces with micro- and nano-structures to improve their biocompatibility, and first of all their osseointegration. These modifications have the potential to address clinical concerns by stimulating different biological processes. This study aims to evaluate the biological responses of ananatase-modified blasted/etched titanium (SLA-anatase) surfaces compared to blasted/acid etched (SLA) and machined titanium surfaces. Using unipolar pulsed direct current (DC) sputtering, a nanocrystalline anatase layer was fabricated. In vitro experiments have shown that SLA-anatase discs can effectively promote osteoblast adhesion and proliferation, which are regarded as important features of a successful dental implant with bone contact. Furthermore, anatase surface modification has been shown to partially enhance osteoblast mineralization in vitro, while not significantly affecting bacterial colonization. Consequently, the recently created anatase coating holds significant potential as a promising candidate for future advancements in dental implant surface modification for improving the initial stages of osseointegration.

Ab initio molecular dynamics of solvation effects and reactivity at the interface between water and ascorbic acid covered anatase TiO2 (101).

In this work, we present a detailed study of the interaction between ascorbic acid (L-asc) and anatase TiO2 (101) surface both in gas phase and in contact with water by using density functional theory and ab initio molecular dynamics simulations. In gas phase, L-asc strongly binds the TiO2 (101) surface as a dianion (L-asc2- ), adopting a bridging bidentate coordination mode (BB), with the two acid protons transferred to two surface 2-fold bridging oxygens (O2c). AIMD simulations show that the interaction between the organic ligand and the anatase surface is stable and comparable to the vacuum one despite the possible solvent effects and/or possible structural distortions of the ligand. In addition, during the AIMD simulations hydroxylation phenomena occur forming transient H3 O+ ions at the solid-liquid interface. For the first time, our results provide insight into the role of the ascorbic acid on the electronic properties of the TiO2 (101), the influence of the water environment on the ligand-surface interaction and the nature of the solid-liquid interface.