Enhancing Oxygen Evolution Reaction Performance in Prussian Blue Analogues: Triple-Play of Metal Exsolution, Hollow Interiors, and Anionic Regulation.

Prussian blue analogs (PBAs) are promising catalysts for green hydrogen production. However, the rational design of high-performing PBAs is challenging, which requires an in-depth understanding of the catalytic mechanism. Here FeMn@CoNi core-shell PBAs are employed as precursors, together with Se powders, in low-temperature pyrolysis in an argon atmosphere. This synthesis method enables the partial dissociation of inner FeMn PBAs that results in hollow interiors, Ni nanoparticles (NPs) exsolution to the surface, and Se incorporation onto the PBA shell. The resulting material presents ultralow oxygen evolution reaction (OER) overpotential (184 mV at 10 mA cm-2 ) and low Tafel slope (43.4 mV dec-1 ), outperforming leading-edge PBA-based electrocatalysts. The mechanism responsible for such a high OER activity is revealed, assisted by density functional theory (DFT) calculations and the surface examination before and after the OER process. The exsolved Ni NPs are found to help turn the PBAs into Se-doped core-shell metal oxyhydroxides during the OER, in which the heterojunction with Ni and the Se incorporation are combined to improve the OER kinetics. This work shows that efficient OER catalysts could be developed by using a novel synthesis method backed up by a sound understanding and control of the catalytic pathway.

Controlled Self-Assembly of Hollow Core-Shell FeMn/CoNi Prussian Blue Analogs with Boosted Electrocatalytic Activity.

Prussian blue analogs (PBAs) are considered as efficient catalysts for energy-related applications due to their porous nanoscale architectures containing finely disseminated active sites. Their catalytic capability can be greatly boosted by the rational design and construction of complex PBA hybrid nanostructures. However, present-day structure engineering inevitably involves additional etchant or procedure. Herein, a facile, yet controllable one-pot self-assembly strategy is introduced to prepare hierarchical core-shell polymetallic PBAs (featuring bimetallic FeMn PBAs cores and CoNi PBAs shells) with hollow nano-cages/solid nano-cube architectures. The detailed characterization of material morphology/composition, assisted with theoretical simulations, reveals the underlying formation mechanism where the key factor is the control of the nucleation rate via the use of chelating agent (citrates) and reaction kinetics. The resulting FeMn@CoNi-H compound is found to accelerate the oxygen evolution reaction activity with a low overpotential (236 mV at a current density 10 mA cm-2 ) as well as a low Tafel slope (58.4 mV dec-1 ). Such an impressive performance is endowed by the rational compositional and structural design with optimized electronic structures as well as an increase in exposed active sites. This work provides a robust, cost-effective pathway that enables chemical and morphological control in creating high-performance catalysts for water electrolysis.

Photoirradiation-Induced Capacitance Enhancement in the h-WO3/Bi2WO6 Submicron Rod Heterostructure under Simulated Solar Illumination and Its Postillumination Capacitance Enhancement Retainment from a Photocatalytic Memory Effect.

Recently, photoassisted charging has been demonstrated as a green and sustainable approach to successfully enhance the capacitance of supercapacitors with low cost and good efficiency. However, their light-induced capacitance enhancement is relatively low and is lost quickly when the illumination is off. In this work, a novel active material system is developed for supercapacitors with the photoassisted charging capability by the decoration of a small amount of Bi2WO6 nanoparticles on an h-WO3 submicron rod surface in situ, which forms a typical type II band alignment heterostructure with a close contact interface through the co-sharing of W atoms between h-WO3 submicron rods and Bi2WO6 nanoparticles. The photogenerated charge carrier separation and transfer are largely enhanced in the h-WO3/Bi2WO6 submicron rod electrode, which subsequently allows more charge carriers to participate in its photoassisted charging process to largely enhance its capacitance improvement under simulated solar illumination than that of the h-WO3 submicron rod electrode. Furthermore, the h-WO3/Bi2WO6 submicron rod electrode could retain its photoinduced capacitance enhancement in the dark for an extended period of time from the photocatalytic memory effect. Thus, our work provides a solution to the two major drawbacks of reported supercapacitors with the light-induced capacitance enhancement property, and supercapacitors based on active materials with the photocatalytic memory effect could be utilized in various technical fields.

Directing photocatalytic pathway to exceedingly high antibacterial activity in water by functionalizing holey ultrathin nanosheets of graphitic carbon nitride.

Metal-free polymeric carbon nitride (C3N4) photocatalysts offer attractive technological advantages over the conventional transition metal oxides or sulfides -based photocatalysts in water disinfection, but their antimicrobial activities are limited by their rapid charge carrier recombination and low specific surface areas. By controlling photocatalytic pathways, we obtained in amino-rich holey ultrathin g-C3N4 nanosheets (AHUCN) a highly efficient inactivation rate against E-coli, which is the highest among the monolithic g-C3N4 and exceeds the antibacterial performance of the most of the previously reported g-C3N4-based photocatalysts. Both the experiments and theoretical calculations demonstrated that the high photocatalytic disinfection performance of AHUCN was derived from the synergistic advantages of their unique holey ultrathin structure and the amino - rich surface in controlling the charge separation and transfer, and most importantly in increasing the photo-production of the dominant antibacterial species, H2O2. From the analysis of the reactive oxygen species and rotating disk electrode (RDE) measurements, it was found that the presence of abundant surface amino groups enabled the switch of the oxygen-reduction pathway from the two-step single-electron indirect reduction on holey ultrathin g-C3N4 nanosheets (HUCN) to the one-step two-electron direct reduction on AHUCN. The switch of the H2O2 production pathway not only facilitated the separation of photogenerated electron-hole pairs but also promoted the generation of reactive oxygen species, greatly enhancing photocatalytic disinfection efficiency.

Post-illumination activity of SnO2 nanoparticle-decorated Cu2O nanocubes by H2O2 production in dark from photocatalytic "memory".

Most photocatalysts only function under illumination, while many potential applications require continuous activities in dark. Thus, novel photocatalysts should be developed, which could store part of their photoactivity in "memory" under illumination and then be active from this "memory" after the illumination is turned off for an extended period of time. Here a novel composite photocatalyst of SnO2 nanoparticle-decorated Cu2O nanocubes is developed. Their large conduction band potential difference and the inner electrostatic field formed in the p-n heterojunction provide a strong driving force for photogenerated electrons to move from Cu2O to SnO2 under visible light illumination, which could then be released to react with O2 in dark to produce H2O2 for its post-illumination activity. This work demonstrates that the selection of decoration components for photocatalysts with the post-illumination photocatalytic "memory" could be largely expanded to semiconductors with conduction band potentials less positive than the two-electron reduction potential of O2.

Synthesis of Superparamagnetic Core-Shell Structure Supported Pd Nanocatalysts for Catalytic Nitrite Reduction with Enhanced Activity, No Detection of Undesirable Product of Ammonium, and Easy Magnetic Separation Capability.

Superparamagnetic nanocatalysts could minimize both the external and internal mass transport limitations and neutralize OH(-) produced in the reaction more effectively to enhance the catalytic nitrite reduction efficiency with the depressed product selectivity to undesirable ammonium, while possess an easy magnetic separation capability. However, commonly used qusi-monodispersed superparamagnetic Fe3O4 nanosphere is not suitable as catalyst support for nitrite reduction because it could reduce the catalytic reaction efficiency and the product selectivity to N2, and the iron leakage could bring secondary contamination to the treated water. In this study, protective shells of SiO2, polymethylacrylic acid, and carbon were introduced to synthesize Fe3O4@SiO2/Pd, Fe3O4@PMAA/Pd, and Fe3O4@C/Pd catalysts for catalytic nitrite reduction. It was found that SiO2 shell could provide the complete protection to Fe3O4 nanosphere core among these shells. Because of its good dispersion, dense structure, and complete protection to Fe3O4, the Fe3O4@SiO2/Pd catalyst demonstrated the highest catalytic nitrite reduction activity without the detection of NH4(+) produced. Due to this unique structure, the activity of Fe3O4@SiO2/Pd catalysts for nitrite reduction was found to be independent of the Pd nanoparticle size or shape, and their product selectivity was independent of the Pd nanoparticle size, shape, and content. Furthermore, their superparamagnetic nature and high saturation magnetization allowed their easy magnetic separation from treated water, and they also demonstrated a good stability during the subsequent recycling experiment.

Synthesis of Mn3O4/CeO2 Hybrid Nanotubes and Their Spontaneous Formation of a Paper-like, Free-Standing Membrane for the Removal of Arsenite from Water.

One-dimensional nanomaterials may organize into macrostructures to have hierarchically porous structures, which could not only be easily adopted into various water treatment apparatus to solve the separation issue of nanomaterials from water but also take full advantage of their nanosize effect for enhanced water treatment performance. In this work, a novel template-based process was developed to create Mn3O4/CeO2 hybrid nanotubes, in which a redox reaction happened between the OMS-2 nanowire template and Ce(NO3)3 to create hybrid nanotubes without the template removal process. Both the Ce/Mn ratio and the precipitation agent were found to be critical in the formation of Mn3O4/CeO2 hybrid nanotubes. Because of their relatively large specific surface area, porous structure, high pore volume, and proper surface properties, these Mn3O4/CeO2 hybrid nanotubes demonstrated good As(III) removal performances in water. These Mn3O4/CeO2 hybrid nanotubes could form paper-like, free-standing membranes spontaneously by a self-assembly process without high temperature treatment, which kept the preferable properties of Mn3O4/CeO2 hybrid nanotubes while avoiding the potential nanomaterial dispersion problem. Thus, they could be readily utilized in commonly used flow-through reactors for water treatment purposes. This approach could be further applied to other material systems to create various hybrid nanotubes for a broad range of technical applications.

Synthesis of tin oxide nanospheres under ambient conditions and their strong adsorption of As(III) from water.

The development of highly efficient As(iii) adsorbents is critical to largely simplify the arsenic treatment process and lower its cost. For the first time, SnO2 nanospheres were demonstrated to possess a highly efficient As(iii) adsorption capability from water in a near neutral pH environment as predicted by the material criterion we recently developed for the selection of highly efficient arsenic adsorbents. These SnO2 nanospheres were synthesized by a simple and cost-effective hydrolysis process with the assistance of ethyl acetate under ambient conditions, which had a good dispersity, a narrow size distribution, a relatively large specific surface area, and a porous structure. A fast As(iii) adsorption was observed in the kinetics study on these SnO2 nanospheres, and their Langmuir adsorption capacity was determined to be ∼112.7 mg g(-1) at pH ∼7. The As(iii) adsorption mechanism on SnO2 nanospheres was examined by both macroscopic and microscopic techniques, which demonstrated that it followed the inner-sphere complex model. These SnO2 nanospheres demonstrated effective As(iii) adsorption even with exceptionally high concentrations of co-existing ions, and a good regeneration capability by washing with NaOH solution.

Real time, in situ observation of the photocatalytic inactivation of Saccharomyces cerevisiae cells.

An in situ microscopy technique was developed to observe in real time the photocatalytic inactivation process of Saccharomyces cerevisiae (S. cerevisiae) cells by palladium-modified nitrogen-doped titanium oxide (TiON/PdO) under visible light illumination. The technique was based on building a photocatalytic micro-reactor on the sample stage of a fluorescence/phase contrast microscopy capable of simultaneously providing the optical excitation to activate the photocatalyst in the micro-reactor and the illumination to acquire phase contrast images of the cells undergoing the photocatalytic inactivation process. Using TiON/PdO as an example, the technique revealed for the first time the vacuolar activities inside S. cerevisiae cells subjected to a visible light photocatalytic inactivation. The vacuoles responded to the photocatalytic attack by the first expansion of the vacuolar volume and then contraction, before the vacuole disappeared and the cell structure collapsed. Consistent with the aggregate behavior observed from the cell culture experiments, the transition in the vacuolar volume provided clear evidence that photocatalytic disinfection of S. cerevisiae cells started with an initiation period in which cells struggled to offset the photocatalytic damage and moved rapidly after the photocatalytic damage overwhelmed the defense mechanisms of the cells against oxidative attack.

Creation of Cu2O@TiO2 composite photocatalysts with p-n heterojunctions formed on exposed Cu2O facets, their energy band alignment study, and their enhanced photocatalytic activity under illumination with visible light.

The creation of photocatalysts with controlled facets has become an important approach to enhance their activity. However, how the formation of heterojunctions on exposed facets could affect their photocatalytic performance ranking had not yet been investigated. In this study, Cu2O@TiO2 core-shell structures were created, and Cu2O/TiO2 p-n heterojunctions were formed on various exposed facets of Cu2O cubes, Cu2O cuboctahedra, and Cu2O octahedra, respectively. These Cu2O@TiO2 polyhedra demonstrated an enhanced photocatalytic degradation effect on Methylene Blue (MB) and 4-nitrophenol (4-NP) under visible light illumination, because of the enhanced charge carrier separation by the formation of Cu2O@TiO2 p-n heterojunctions. It was further found that their photocatalytic performance was also facet-dependent as pure Cu2O polyhedra, while the photocatalytic performance ranking of these Cu2O@TiO2 polyhedra was different with that of their corresponding Cu2O polyhedron cores. By the combination of optical property measurement and XPS analysis, the energy band alignments of these Cu2O@TiO2 polyhedra were determined, which demonstrated that Cu2O@TiO2 octahedra had the highest band offset for the separation of charge carriers. Thus, the charge-carrier-separation-driven force in Cu2O@TiO2 polyhedra was different from their corresponding Cu2O polyhedron cores, which resulted in their different surface photovoltage spectrum (SPS) responses and different photocatalytic performance rankings.

Synthesis of Cu2O nanospheres decorated with TiO2 nanoislands, their enhanced photoactivity and stability under visible light illumination, and their post-illumination catalytic memory.

A novel Cu2O/TiO2 composite photocatalyst structure of Cu2O nanospheres decorated with TiO2 nanoislands were synthesized by a facile hydrolyzation reaction followed by a solvent-thermal process. In this Cu2O/TiO2 composite photocatalyst, Cu2O served as the main visible light absorber, while TiO2 nanoislands formed heterojunctions of good contact with Cu2O, beneficial to the photoexcited electron transfer between them. Their band structure match and inner electrostatic field from the p-n heterojunction both favored the transfer of photoexcited electrons from Cu2O to TiO2, which effectively separated the electron-hole pairs. Photogenerated holes on Cu2O could react with water or organic pollutants/microorganisms in water to avoid accumulation on Cu2O because of the partial TiO2 nanoislands coverage, which enhanced their stability during the photocatalysis process. Their superior photocatalytic performance under visible light illumination was demonstrated in both the degradation of methyl orange and the disinfection of Escherichia coli bacteria. An interesting post-illumination catalytic memory was also observed for this composite photocatalyst as demonstrated in the disinfection of Escherichia coli bacteria in the dark after the visible light was shut off, which could be attributed to the transfer of photoexcited electrons from Cu2O to TiO2 and their trapping on TiO2 under visible light illumination, and their release in the dark after the visible light was shut off.

Antifungal activity and mechanism of palladium-modified nitrogen-doped titanium oxide photocatalyst on agricultural pathogenic fungi Fusarium graminearum.

Fusarium graminearum is the pathogen for Fusarium head blight (FHB) on wheat, which could significantly reduce grain quality/yield and produce a variety of mycotoxins posing a potential safety concern to human foods. As an environmentally friendly alternative to the commonly used chemical fugicides, a highly effective photocatalytic disinfection of F. graminearum macroconidia under visible light illumination was demonstrated on a visible-light-activated palladium-modified nitrogen-doped titanium oxide (TiON/PdO) nanoparticle photocatalyst. Because of the opposite surface charges of the TiON/PdO nanoparticles and the F. graminearum macroconidium, the nanoparticles were strongly adsorbed onto the macroconidium surface, which is beneficial to the photocatalytic disinfection of these macroconidia. The photocatalytic disinfection mechanism of TiON/PdO nanoparticles on these macroconidia could be attributed to their cell wall/membrane damage caused by the attack from reactive oxygen species (ROSs) as demonstrated by the fluorescence/phase contrast microscopy observations, while a breakage of their cell structure was not necessary for their loss of viability.

Exceptional arsenic (III,V) removal performance of highly porous, nanostructured ZrO2 spheres for fixed bed reactors and the full-scale system modeling.

Highly porous, nanostructured zirconium oxide spheres were fabricated from ZrO2 nanoparticles with the assistance of agar powder to form spheres with size at millimeter level followed with a heat treatment at 450 °C to remove agar network, which provided a simple, low-cost, and safe process for the synthesis of ZrO2 spheres. These ZrO2 spheres had a dual-pore structure, in which interconnected macropores were beneficial for liquid transport and the mesopores could largely increase their surface area (about 98 m(2)/g) for effective contact with arsenic species in water. These ZrO2 spheres demonstrated an even better arsenic removal performance on both As(III) and As(V) than ZrO2 nanoparticles, and could be readily applied to commonly used fixed-bed adsorption reactors in the industry. A short bed adsorbent test was conducted to validate the calculated external mass transport coefficient and the pore diffusion coefficient. The performance of full-scale fixed bed systems with these ZrO2 spheres as the adsorber was estimated by the validated pore surface diffusion modeling. With the empty bed contact time (EBCT) at 10 min and the initial arsenic concentration at 30 ppb, the number of bed volumes that could be treated by these dry ZrO2 spheres reached ~255,000 BVs and ~271,000 BVs for As(III) and As(V), respectively, until the maximum contaminant level of 10 ppb was reached. These ZrO2 spheres are non-toxic, highly stable, and resistant to acid and alkali, have a high arsenic adsorption capacity, and could be easily adapted for various arsenic removal apparatus. Thus, these ZrO2 spheres may have a promising potential for their application in water treatment practice.

Strong adsorption of phosphate by amorphous zirconium oxide nanoparticles.

Phosphate removal is important in the control of eutrophication of water bodies. Adsorption is one of the promising approaches for the removal of phosphate, which could serve as a supplement for the biological phosphate removal process commonly used in the wastewater treatment industry to meet the discharge requirement when the biological performance is deteriorated from changes of operation conditions. Amorphous zirconium oxide nanoparticles were synthesized by a simple and low-cost hydrothermal process, and their phosphate removal performance was explored in aqueous environment under various conditions. A fast adsorption of phosphate was observed in the kinetics study, and their adsorption capacity was determined at about 99.01 mg/g at pH 6.2 in the equilibrium adsorption isotherm study. Commonly coexisting anions showed no or minimum effect on their phosphate adsorption performance. The phosphate adsorption showed little pH dependence in the range from pH 2 to 6, while it decreased sharply with the pH increase above pH 7. After adsorption, phosphate on these am-ZrO2 nanoparticles could be easily desorbed by NaOH solution washing. Both the macroscopic and microscopic techniques demonstrated that the phosphate adsorption mechanism of am-ZrO2 nanoparticles followed the inner-sphere complexing mechanism, and the surface hydroxyl groups played a key role in the phosphate adsorption.

Superparamagnetic magnesium ferrite nanoadsorbent for effective arsenic (III, V) removal and easy magnetic separation.

By doping a proper amount of Mg(2+) (~10%) into α-Fe2O3 during a solvent thermal process, ultrafine magnesium ferrite (Mg0.27Fe2.50O4) nanocrystallites were successfully synthesized with the assistance of in situ self-formed NaCl "cage" to confine their crystal growth. Their ultrafine size (average size of ~3.7 nm) and relatively low Mg-content conferred on them a superparamagnetic behavior with a high saturation magnetization (32.9 emu/g). The ultrafine Mg0.27Fe2.50O4 nanoadsorbent had a high specific surface area of ~438.2 m(2)/g, and demonstrated a superior arsenic removal performance on both As(III) and As(V) at near neutral pH condition. Its adsorption capacities on As(III) and As(V) were found to be no less than 127.4 mg/g and 83.2 mg/g, respectively. Its arsenic adsorption mechanism was found to follow the inner-sphere complex mechanism, and abundant hydroxyl groups on its surface played the major role in its superior arsenic adsorption performance. It could be easily separated from treated water bodies with magnetic separation, and could be easily regenerated and reused while maintaining a high arsenic removal efficiency. This novel superparamagnetic magnesium ferrite nanoadsorbent may offer a simple single step adsorption treatment option to remove arsenic contamination from water without the pre-/post-treatment requirement for current industrial practice.

The synthesis of nitrogen/sulfur co-doped TiO2 nanocrystals with a high specific surface area and a high percentage of {001} facets and their enhanced visible-light photocatalytic performance.

Nitrogen/sulfur co-doped anatase TiO2 nanocrystals with a high specific surface area and a high percentage of {001} facets were synthesized by a solvent-thermal process followed by the calcination with thiourea at an optimum heat treatment temperature. Under current experimental conditions, the optimum heat treatment temperature was found at 300°C, which successfully introduced nitrogen and sulfur dopants into the anatase lattice to replace a small portion of oxygen atoms while preserving the geometry of these anatase TiO2 nanocrystals to maintain a high percentage of {001} facets. These nitrogen/sulfur co-doped anatase TiO2 nanocrystals demonstrated a largely enhanced light absorption in the whole visible-light range and exhibited much higher photocatalytic performance than both P25 TiO2 nanoparticles and anatase TiO2 nanocrystals with a high percentage of {001} facets under visible-light illumination.

NH4+ directed assembly of zinc oxide micro-tubes from nanoflakes.

A simple precipitation process followed with the heat treatment was developed to synthesize ZnO micro-tubes by self-assembly of nanoflakes composed of nanoparticles. The resulting ZnO micro-tubes demonstrated excellent photocatalytic performance in degrading methylene blue (MB) under UV illumination. It was found that NH4+ ion played a critical role in directing the assembly of the nanoflakes to form the micro-tube structure. A critical reaction ratio existed at or above which the ZnO micro-tubes could be obtained. For the mixtures of solutions of (NH4)2CO3 and zinc salt, the ratio () was 2:1.

Arsenic (III,V) removal from aqueous solution by ultrafine α-Fe2O3 nanoparticles synthesized from solvent thermal method.

Ultrafine iron oxide (α-Fe(2)O(3)) nanoparticles were synthesized by a solvent thermal process and used to remove arsenic ions from both lab-prepared and natural water samples. The α-Fe(2)O(3) nanoparticles assumed a near-sphere shape with an average size of about 5 nm. They aggregated into a highly porous structure with a high specific surface area of ∼ 162 m(2)/g, while their surface was covered by high-affinity hydroxyl groups. The arsenic adsorption experiment results demonstrated that they were effective, especially at low equilibrium arsenic concentrations, in removing both As(III) and As(V) from lab-prepared and natural water samples. Near the neutral pH, the adsorption capacities of the α-Fe(2)O(3) nanoparticles on As(III) and As(V) from lab-prepared samples were found to be no less than 95 mg/g and 47 mg/g, respectively. In the presence of most competing ions, these α-Fe(2)O(3) nanoparticles maintained their arsenic adsorption capacity even at very high competing anion concentrations. Without the pre-oxidation and/or the pH adjustment, these α-Fe(2)O(3) nanoparticles effectively removed both As(III) and As(V) from a contaminated natural lake water sample to meet the USEPA drinking water standard for arsenic.

Visible-light-induced bactericidal activity of titanium dioxide codoped with nitrogen and silver.

Titanium dioxide nanoparticles codoped with nitrogen and silver (Ag(2)O/TiON) were synthesized by the sol-gel process and found to be an effective visible light driven photocatalyst. The catalyst showed strong bactericidal activity against Escherichia coli (E. coli) under visible light irradiation (λ > 400 nm). In X-ray photoelectron spectroscopy and X-ray diffraction characterization of the samples, the as-added Ag species mainly exist as Ag(2)O. Spin trapping EPR study showed Ag addition greatly enhanced the production of hydroxyl radicals (•OH) under visible light irradiation. The results indicate that the Ag(2)O species trapped e(CB)(-) in the process of Ag(2)O/TiON photocatalytic reaction, thus inhibiting the recombination of e(CB)(-) and h(VB)(+) in agreement with the stronger photocatalytic bactericidal activity of Ag(2)O/TiON. The killing mechanism of Ag(2)O/TiON under visible light irradiation is shown to be related to oxidative damages in the forms of cell wall thinning and cell disconfiguration.

As(III) removal by hydrous titanium dioxide prepared from one-step hydrolysis of aqueous TiCl(4) solution.

Hydrous titanium dioxide (TiO(2)·xH(2)O) nanoparticles were synthesized by a low-cost one-step hydrolysis process with aqueous TiCl(4) solution. These TiO(2)·xH(2)O nanoparticles ranged from 3 to 8 nm and formed aggregates with a highly porous structure, resulting in a large surface area and easy removal capability from aqueous environment after the treatment. Their effectiveness on the removal of As(III) (arsenite) from water was investigated in both laboratory and natural water samples. The adsorption capacity on As(III) of these TiO(2)·xH(2)O nanoparticles reached over 83 mg/g at near neutral pH environment, and over 96 mg/g at pH 9.0. Testing with a As(III) contaminated natural lake water sample confirmed the effectiveness of these TiO(2)·xH(2)O nanoparticles in removing As(III) from natural water. The high adsorption capacity of the TiO(2)·xH(2)O nanoparticles is related to the high surface area, large pore volume, and the presence of high affinity surface hydroxyl groups.