Crystal Design and Photoactivity of TiO2 Nanorod Template Decorated with Nanostructured Bi2S3 Visible Light Sensitizer.

In this study, TiO2-Bi2S3 composites with various morphologies were synthesized through hydrothermal vulcanization with sputtering deposited Bi2O3 sacrificial layer method on the TiO2 nanorod templates. The morphologies of decorated Bi2S3 nanostructures on the TiO2 nanorod templates are controlled by the duration of hydrothermal vulcanization treatment. The Bi2S3 crystals in lumpy filament, nanowire, and nanorod feature were decorated on the TiO2 nanorod template after 1, 3, and 5 h hydrothermal vulcanization, respectively. Comparatively, TiO2-Bi2S3 composites with Bi2S3 nanowires exhibit the best photocurrent density, the lowest interfacial resistance value and the highest photodegradation efficiency towards Rhodamine B solution. The possible Z-scheme photoinduced charge separation mechanism and suitable morphology of Bi2S3 nanowires might account for the high photoactivity of TiO2 nanorod-Bi2S3 nanowire composites.

Boosting photoresposive ability of WO3-Bi2O3nanocomposite rods via annealing-induced intrinsic precipitation of nanosized Bi particles.

In this study, Bi-particle-functionalized tungsten trioxide-bismuth oxide (WO3-Bi2O3) composite nanorods were prepared by integrating sputtering and hydrothermal syntheses with an appropriate postannealing procedure to induce Bi particle precipitation. Unlike other routes in which metal particle decoration is achieved externally, in this study, photoresponsive one-dimensional WO3-Bi2O3composite nanorods were decorated with Bi particles by using the internal precipitation method. Structural analysis revealed that the Bi-metal-particle-functionalized WO3-Bi2O3composite nanorods with particle size ranging from 5 to 10 nm were formed through hydrogen gas annealing at an optimal annealing temperature of 350 °C. Compared with the pristine WO3nanorod template, the Bi-WO3-Bi2O3composite nanorods exhibited higher photoresponsive performance, substantial photogenerated charge transfer ability, and efficient separation of photogenerated electron-hole pairs. The study results indicated that the Bi-WO3-Bi2O3composite nanorods had superior decontamination ability and excellent stability toward RhB dye as compared with pristine WO3. Moreover, the photogenerated charge separation and migration efficiencies of the WO3-Bi2O3nanorods could be tuned through appropriate reduction of the surface oxide layer; this is a promising approach to designing WO3-Bi2O3nanorods with high photoactive performance.

Enhanced Sensing Ability of Brush-Like Fe2O3-ZnO Nanostructures towards NO2 Gas via Manipulating Material Synergistic Effect.

Brush-like α-Fe2O3-ZnO heterostructures were synthesized through a sputtering ZnO seed-assisted hydrothermal growth method. The resulting heterostructures consisted of α-Fe2O3 rod templates and ZnO branched crystals with an average diameter of approximately 12 nm and length of 25 nm. The gas-sensing results demonstrated that the α-Fe2O3-ZnO heterostructure-based sensor exhibited excellent sensitivity, selectivity, and stability toward low-concentration NO2 gas at an optimal temperature of 300 °C. The α-Fe2O3-ZnO sensor, in particular, demonstrated substantially higher sensitivity compared with pristine α-Fe2O3, along with faster response and recovery speeds under similar test conditions. An appropriate material synergic effect accounts for the considerable enhancement in the NO2 gas-sensing performance of the α-Fe2O3-ZnO heterostructures.

Design and tuning functionality of rod-like titanium dioxide-nickel oxide composites via a combinational methodology.

TiO2-NiO composite nanorods were synthesized by combining hydrothermal growth of TiO2 nanorods and sputtering deposition of NiO film. Crystalline NiO coverage films with various thicknesses were sputter coated onto TiO2 nanorods by controlling NiO sputtering duration. The crystallographic analyses demonstrate that crystalline rutile TiO2-cubic NiO composite nanorods were formed herein. In comparison with pristine TiO2 and NiO, the coverage of NiO crystals on the TiO2 nanorods led to an enhanced photodegradation activity of the TiO2-NiO composites towards Rhodamine B dyes under irradiation. Moreover, the TiO2-NiO composite nanorods with the adequate content of NiO coverage layer show superior gas-sensing responses to 25-200 ppm ammonia gas in comparison with those of the constituent counterparts. The experimental results herein demonstrate that decoration of NiO film on the surfaces of TiO2 nanorods with tunable coverage sizes via sputtering deposition is a promising approach to design TiO2-NiO composite nanorods with desirable functionalities.

Sputtering control of Ag2O decoration configurations on ZnO nanorods and their surface arrangement effects on photodegradation ability toward methyl orange.

In this study, a combinational strategy for synthesizing ZnO nanorod arrays interlaced with Ag2O particles was proposed. Hydrothermally derived ZnO nanorod templates were sputter coated with Ag2O particles. The sputtered Ag2O particles can be decorated on the surfaces of the ZnO nanorod arrays with a randomly dispersive or continuous coverage characteristic by controlling the sputtering duration. Structural analysis revealed the formation of satisfactory crystalline ZnO-Ag2O composite nanorods through the hydrothermal and sputtering methods. The ZnO-Ag2O composite nanorods exhibited a significantly enhanced photoactivity compared with that of pristine ZnO nanorods under light irradiation. Moreover, the Ag2O content and the coverage feature of the ZnO-Ag2O composite nanorods influence the photodegradation of methyl orange solution by the composite nanorods under light irradiation. The photodegradation efficiency of the ZnO nanorods was substantially enhanced when the Ag2O particles were decorated on the surfaces in a dispersive manner. This can be attributed to the optimal content of Ag2O particles and their randomly dispersive characteristic on the surface of the composite nanorods, which resulted in the efficient transfer of photocarriers and markedly suppressed the electron-hole recombination rate.

Controllable Crystal Growth and Improved Photocatalytic Activity of Porous Bi2O3-Bi2S3 Composite Sheets.

Porous Bi2O3-Bi2S3 composite sheets were constructed through a combinational methodology of chemical bath deposition and hydrothermal reaction. The Na2S precursor concentration in the hydrothermal solution was varied to understand the correlation between the vulcanization degree and structure evolution of the porous Bi2O3-Bi2S3 composite sheets. The control of the etching rate of the Bi2O3 sheet template and the regrowth rate of Bi2S3 crystallites via suitable sulfide precursor concentration during the hydrothermal reaction utilizes the formation of porous Bi2O3-Bi2S3 sheets. Due to the presence of Bi2S3 crystallites and porous structure in the Bi2O3-Bi2S3 composites, the improved visible-light absorption ability and separation efficiency of photogenerated charge carriers are achieved. Furthermore, the as-synthesized Bi2O3-Bi2S3 composite sheets obtained from vulcanization with a 0.01M Na2S precursor display highly enhanced photocatalytic degradation toward methyl orange (MO) dyes compared with the pristine Bi2O3 and Bi2S3. The porous Bi2O3-Bi2S3 sheet system shows high surface active sites, fast transfer, high-efficiency separation of photoinduced charge carriers, and enhanced redox capacity concerning their constituent counterparts. This study affords a promising approach to constructing Bi2O3-based Z-scheme composites with a suitable microstructure and Bi2O3/Bi2S3 phase ratio for photoactive device applications.

Sputtering-Assisted Synthesis of Copper Oxide-Titanium Oxide Nanorods and Their Photoactive Performances.

A TiO2 nanorod template was successfully decorated with a copper oxide layer with various crystallographic phases using sputtering and postannealing procedures. The crystallographic phase of the layer attached to the TiO2 was adjusted from a single Cu2O phase or dual Cu2O-CuO phase to a single CuO phase by changing the postannealing temperature from 200 °C to 400 °C. The decoration of the TiO2 (TC) with a copper oxide layer improved the light absorption and photoinduced charge separation abilities. These factors resulted in the composite nanorods demonstrating enhanced photoactivity compared to that of the pristine TiO2. The ternary phase composition of TC350 allowed it to achieve superior photoactive performance compared to the other composite nanorods. The possible Z-scheme carrier movement mechanism and the larger granular size of the attached layer of TC350 under irradiation accounted for the superior photocatalytic activity in the degradation of RhB dyes.

Crystal Growth and Design of Disk/Filament ZnO-Decorated 1D TiO2 Composite Ceramics for Photoexcited Device Applications.

Disk- and filament-like ZnO crystals were decorated on one-dimensional TiO2 nanostructures (TiO2-ZnO) through various integrated physical and chemical synthesis methods. The morphology of the ZnO crystals on TiO2 varied with the chemical synthesis method used. ZnO nanodisks decorated with TiO2 nanorods (TiO2-ZnO-C) were synthesized using the chemical bath deposition method, and ZnO filament-like crystals decorated with TiO2 nanorods (TiO2-ZnO-H) were synthesized through the hydrothermal method. Compared with the pristine TiO2 nanorods, the as-synthesized TiO2-ZnO composites exhibited enhanced photophysiochemical performance. Furthermore, because of their fast electron transportation and abundant surface active sites, the ZnO nanodisks in the TiO2-ZnO-C composite exhibited a higher photoactivity than those in the TiO2-ZnO-H composite. The morphology and crystal quality of the ZnO decoration layer were manipulated using different synthesis methods to realize disk- or filament-like ZnO-decorated TiO2 composites with various photoactive performance levels.

Formation and Application of Core-Shell of FePt-Au Magnetic-Plasmonic Nanoparticles.

Monodispersed FePt core and FePt-Au core-shell nanoparticles (NPs) have been chemically synthesized in liquid solution and with controllable surface-functional properties. The NP size was increased from 2.5 nm for FePt to 6.5 nm for FePt-Au, which could be tuned by the initial concentration of gold acetate coated onto FePt seeding NPs via a seed-mediated formation of self-assembled core-shell nanostructures. The analyses of the interplanar spacing obtained from the high-resolution transmission electron microscopy (HRTEM), selective electron diffraction pattern (SAED), and x-ray diffraction (XRD) confirmed that both FePt core and Au shell belong to the face-centered cubic (fcc) structure. FePt-Au NPs have a surface plasmon resonance (SPR) peak at 528 nm in the visible optical band region, indicating the red shift compared with the typical theoretical value of 520 nm of pure Au NPs. The surface modification and ligand exchange of FePt-Au was using mercaptoacetic acid (thiol) as a phase transfer reagent that turned the NPs hydrophilic due to the functional carboxyl group bond on the surface of presented multifunctional magnetic-plasmonic NPs. The water-dispersible FePt-based NPs conjugated with biomolecules could reach the different biocompatibility requirements and also provide enough heating response that acted as a potential agent for magnetic fluid hyperthermia in biomedical engineering research fields.

Design of Hydrothermally Derived Fe2O3 Rods with Enhanced Dual Functionality Via Sputtering Decoration of a Thin ZnO Coverage Layer.

The Fe2O3-ZnO composite rods were successfully synthesized by combining hydrothermal growth of Fe2O3 rods and sputtering deposition of a thin ZnO coverage layer. Two types of the Fe2O3 rods with round and rectangular cross-sectional morphologies grown via control of the urea content in hydrothermal growth processes were used as rod templates to fabricate the Fe2O3-ZnO composite rods. The Fe2O3-ZnO composite rods exhibited an improved photoelectric conversion efficiency in the Fe2O3 rods via a construction of a heterogeneous structure. The photocatalytic degradation performance of rhodamine B dyes with Fe2O3 rods was substantially increased via sputtering decoration of a thin ZnO coverage layer on the Fe2O3 rods. Moreover, the Fe2O3-ZnO composite rods exhibited superior acetone vapor-sensing responses than the pristine Fe2O3 rods herein. The extended optical absorption ability together with the enhanced photoinduced charge separation efficiency via construction of the Fe2O3-ZnO heterogeneous system explained the improved photoactivity of the composite rods. Furthermore, the formation of a heterojunction between the Fe2O3 and ZnO increased the interfacial potential barrier height and enhanced the sensor resistance variation size upon exposure to the acetone vapor. This accounted for the improved gas-sensing performance of the Fe2O3-ZnO composite rods. The experimental results herein provide a promising approach to design Fe2O3-based composite rods with desirable photocatalytic and gas-sensing functionalities.

Improved photoelectrode performance of chemical solution-derived Bi2O3 crystals via manipulation of crystal characterization.

Three-dimensional Bi2O3 crystals with various morphologies were successfully synthesized on F-doped tin oxide substrates with and without homoseed layers via chemical bath deposition (CBD) routes. The structural analysis reveals that control of the pH value of the reaction solution resulted in as-grown Bi2O3 crystals with nanosheet and plate morphologies. A lower pH value of the reaction solution engendered formation of a porous sheet-like morphology of Bi2O3; by contrast, a higher pH value of the reaction solution is favorable for formation of solid Bi2O3 plates on the substrates. Furthermore, a sputter coated Bi2O3 seed layer with dual α- and ß-Bi2O3 phases plays an important role in the CBD-derived Bi2O3 crystallographic structures. The Bi2O3 crystals formed via CBD processes without a sputter coated Bi2O3 homoseed layer demonstrated a high purity in ß-Bi2O3 phase; those grown with a homoseed layer exhibited a dual α/ß phase. The photoactive performance results show that construction of an α/ß-Bi2O3 homojunction in the CBD-derived Bi2O3 crystals substantially improved their photoactive performance. Comparatively, the porous Bi2O3 nanosheets with a dual α/ß-Bi2O3 phase demonstrated the highest photoactive performance among various Bi2O3 crystals in this study. The superior photoactivity of the porous α/ß-Bi2O3 nanosheets herein is attributed to their high light absorption capacity and photoinduced charge separation efficiency. The experimental results in this study provide a promising approach to design CBD-derived Bi2O3 crystals with desirable photoelectric conversion functions via facile morphology control and seed layer crystal engineering.

Coverage Layer Phase Composition-Dependent Photoactivity of One-Dimensional TiO2-Bi2O3 Composites.

TiO2-Bi2O3 composite rods were synthesized by combining hydrothermal growth of rutile TiO2 rod templates and sputtering deposition of Bi2O3 thin films. The TiO2-Bi2O3 composite rods with ß-Bi2O3 phase and α/ß-Bi2O3 dual-phase decoration layers were designed, respectively, via in situ radio-frequency magnetron sputtering growth and post-annealing procedures in ambient air. The crystal structure, surface morphology, and photo-absorption performances of the pristine TiO2 rods decorated with various Bi2O3 phases were investigated. The crystal structure analysis reveals that the crystalline TiO2-Bi2O3 rods contained ß-Bi2O3 and α/ß-Bi2O3 crystallites were separately formed on the TiO2 rod templates with different synthesis approaches. The morphology analysis demonstrates that the ß-Bi2O3 coverage layer on the crystalline rutile TiO2 rods showed flat layer morphology; however, the surface morphology of the α/ß-Bi2O3 dual-phase coverage layer on the TiO2 rods exhibited a sheet-like feature. The results of photocatalytic decomposition towards methyl orange dyes show that the substantially improved photoactivity of the rutile TiO2 rods was achieved by decorating a thin sheet-like α/ß-Bi2O3 coverage layer. The effectively photoinduced charge separation efficiency in the stepped energy band configuration in the composite rods made from the TiO2 and α/ß-Bi2O3 explained their markedly improved photoactivity. The TiO2-α/ß-Bi2O3 composite rods are promising for use as photocatalysts and photoelectrodes.

Thermal Annealing Induced Controllable Porosity and Photoactive Performance of 2D ZnO Sheets.

Porous ZnO sheets containing various degrees of a nanoscaled pore were successfully synthesized using a simple hydrothermal method and various postannealing procedures. The porosity features of the ZnO sheets can be easily tuned by changing both the annealing temperature and annealing atmosphere. The dense porous nature of ZnO sheets is beneficial to enhance light absorption. Moreover, the substantially increased oxygen vacancies in the ZnO sheets were observed especially after the hydrogen treatment as revealed in the X-ray photoelectron spectroscope and photoluminescence analyses. The high density of surface crystal defect enhanced the photoinduced electron-hole separation rate of the ZnO sheets, which is crucial for an improved photoactivity. The porous ZnO sheets formed at a hydrogen atmosphere exhibited superior photoactive performance than the porous ZnO sheets formed at the high-temperature ambient air annealing. The dense pores and massive crystal defects formed by a hydrogen atmosphere annealing in the ZnO crystals might account for the observed photoactive behaviors in this study.

Design and Synthesis of Novel 2D Porous Zinc Oxide-Nickel Oxide Composite Nanosheets for Detecting Ethanol Vapor.

The porous zinc oxide-nickel oxide (ZnO-NiO) composite nanosheets were synthesized via sputtering deposition of NiO thin film on the porous ZnO nanosheet templates. Various NiO film coverage sizes on porous ZnO nanosheet templates were achieved by changing NiO sputtering duration in this study. The microstructures of the porous ZnO-NiO composite nanosheets were investigated herein. The rugged surface feature of the porous ZnO-NiO composite nanosheets were formed and thicker NiO coverage layer narrowed the pore size on the ZnO nanosheet template. The gas sensors based on the porous ZnO-NiO composite nanosheets displayed higher sensing responses to ethanol vapor in comparison with the pristine ZnO template at the given target gas concentrations. Furthermore, the porous ZnO-NiO composite nanosheets with the suitable NiO coverage content demonstrated superior gas-sensing performance towards 50-750 ppm ethanol vapor. The observed ethanol vapor-sensing performance might be attributed to suitable ZnO/NiO heterojunction numbers and unique porous nanosheet structure with a high specific surface area, providing abundant active sites on the surface and numerous gas diffusion channels for the ethanol vapor molecules. This study demonstrated that coating of NiO on the porous ZnO nanosheet template with a suitable coverage size via sputtering deposition is a promising route to fabricate porous ZnO-NiO composite nanosheets with a high ethanol vapor sensing ability.

Crystal phase content-dependent functionality of dual phase SnO2-WO3 nanocomposite films via cosputtering crystal growth.

In this study, crystalline SnO2-WO3 nanocomposite thin films were grown through radio-frequency cosputtering of metallic Sn and ceramic WO3 targets. The W content in the SnO2 matrix was varied from 5.4 at% to 12.3 at% by changing the WO3 sputtering power during thin-film growth. Structural analyses showed that increased WO3 phase content in the nanocomposite films reduced the degree of crystallization of the SnO2 matrix. Moreover, the size of the composite films' surface crystallites increased with WO3 phase content, and the large surface crystallites were composed of numerous nanograins. Addition of WO3 crystals to the SnO2 matrix to form a composite film improved its light harvesting ability. The SnO2-WO3 nanocomposite films exhibited improved photodegradation ability for Rhodamine B dyes compared with their individual constituents (i.e., SnO2 and WO3 thin films), which is attributable to the suitable type II band alignment between the SnO2 and WO3. Moreover, an optimal WO3 phase content (W content: 5.4 at%) in the SnO2 matrix substantially enhanced the ethanol gas-sensing response of the SnO2 thin film. This suggested that the heterojunctions at the SnO2/WO3 interface regions in the nanocomposite film considerably affected its ethanol gas-sensing behavior.

Enhancement of Acetone Gas-Sensing Responses of Tapered WO3 Nanorods through Sputtering Coating with a Thin SnO2 Coverage Layer.

WO3-SnO2 composite nanorods were synthesized by combining hydrothermal growth of tapered tungsten trioxide (WO3) nanorods and sputter deposition of thin SnO2 layers. Crystalline SnO2 coverage layers with thicknesses in the range of 13-34 nm were sputter coated onto WO3 nanorods by controlling the sputtering duration of the SnO2. The X-ray diffraction (XRD) analysis results demonstrated that crystalline hexagonal WO3-tetragonal SnO2 composite nanorods were formed. The microstructural analysis revealed that the SnO2 coverage layers were in a polycrystalline feature. The elemental distribution analysis revealed that the SnO2 thin layers homogeneously covered the surfaces of the hexagonally structured WO3 nanorods. The WO3-SnO2 composite nanorods with the thinnest SnO2 coverage layer showed superior gas-sensing response to 100-1000 ppm acetone vapor compared to other composite nanorods investigated in this study. The substantially improved gas-sensing responses to acetone vapor of the hexagonally structured WO3 nanorods coated with the SnO2 coverage layers are discussed in relation to the thickness of SnO2 coverage layers and the core-shell configuration of the WO3-SnO2 composite nanorods.

Design of Nanoscaled Surface Morphology of TiO2-Ag2O Composite Nanorods through Sputtering Decoration Process and Their Low-Concentration NO2 Gas-Sensing Behaviors.

TiO2-Ag2O composite nanorods with various Ag2O configurations were synthesized by a two-step process, in which the core TiO2 nanorods were prepared by the hydrothermal method and subsequently the Ag2O crystals were deposited by sputtering deposition. Two types of the TiO2-Ag2O composite nanorods were fabricated; specifically, discrete Ag2O particle-decorated TiO2 composite nanorods and layered Ag2O-encapsulated TiO2 core-shell nanorods were designed by controlling the sputtering duration of the Ag2O. The structural analysis revealed that the TiO2-Ag2O composite nanorods have high crystallinity. Moreover, precise control of the Ag2O sputtering duration realized the dispersive decoration of the Ag2O particles on the surfaces of the TiO2 nanorods. By contrast, aggregation of the massive Ag2O particles occurred with a prolonged Ag2O sputtering duration; this engendered a layered coverage of the Ag2O clusters on the surfaces of the TiO2 nanorods. The TiO2-Ag2O composite nanorods with different Ag2O coverage morphologies were used as chemoresistive sensors for the detection of trace amounts of NO2 gas. The NO2 gas-sensing performances of various TiO2-Ag2O composite nanorods were compared with that of pristine TiO2 nanorods. The underlying mechanisms for the enhanced sensing performance were also discussed.

Improvement of Ethanol Gas-Sensing Responses of ZnO⁻WO3 Composite Nanorods through Annealing Induced Local Phase Transformation.

In this study, ZnO-WO3 composite nanorods were synthesized through a combination of hydrothermal growth and sputtering method. The structural analysis results revealed that the as-synthesized composite nanorods had a homogeneous coverage of WO3 crystallite layer. Moreover, the ZnO-WO3 composite nanorods were in a good crystallinity. Further post-annealed the composite nanorods in a hydrogen-containing atmosphere at 400 °C induced the local phase transformation between the ZnO and WO3. The ZnO-WO3 composite nanorods after annealing engendered the coexistence of ZnWO4 and WO3 phase in the shell layer which increased the potential barrier number at the interfacial contact region with ZnO. This further enhanced the ethanol gas-sensing response of the pristine ZnO-WO3 composite nanorods. The experimental results herein demonstrated a proper thermal annealing procedure of the binary composite nanorods is a promising approach to modulate the gas-sensing behavior the binary oxide composite nanorods.

Microstructures and Photodegradation Performance toward Methylene Orange of Sputtering-Assisted Decoration of ZnFe2O4 Crystallites onto TiO2 Nanorods.

In this study, TiO2⁻ZnFe2O4 (ZFO) core-shell nanorods with various ZFO crystallite thicknesses were synthesized through sputtering-deposited ZFO thin films onto the surfaces of TiO2 nanorods. By coupling the ZFO narrow bandgap oxide with TiO2, an enhanced photodegradation efficiency of methylene orange under irradiation was achieved. Structural analyses revealed that ZFO crystallites fully covered the surfaces of the TiO2 nanorods. The sputtering-deposited ZFO crystallites on the head region of the composite nanorods were markedly thicker than those covering the lateral region of the composite nanorods. The coverage of ZFO crystallites on the TiO2 nanorods led to an improved light harvesting, a decrease in the hole⁻electron recombination rate, as well as the enhanced photodegradation activity of the TiO2⁻ZFO heterostructures under irradiation. The optimized ZFO thickness on the head region of the composite nanorods was approximately 43 nm on average and that at the lateral region of the composite nanorods was 15 nm, which exhibited superior photodegradation ability to methylene orange and retained a stable photodegradation efficiency of approximately 97% after cycling tests. The results herein demonstrate that sputtering deposition of ZFO crystallite with tunable thickness is a promising approach to designing TiO2⁻ZFO composite nanorods with various ZFO coverage sizes and to adjust their photodegradation ability toward organic dyes.

Surface Morphology-Dependent Functionality of Titanium Dioxide-Nickel Oxide Nanocomposite Semiconductors.

In this study, TiO2-NiO heterostructures were synthesized by combining hydrothermal and chemical bath deposition methods. The post-annealing temperature was varied to control the surface features of the TiO2-NiO heterostructures. TiO2-NiO heterostructures annealed at 350 °C comprised NiO-nanosheet-decorated TiO2 nanostructures (NST), whereas those annealed at 500 °C comprised NiO-nanoparticle-decorated TiO2 nanostructures (NPT). The NPT exhibited higher photodegradation activity than the NST in terms of methylene blue (MB) degradation under irradiation. Structural analyses demonstrated that the NPT had a higher surface adsorption capability for MB dyes and superior light-harvesting ability; thus, they exhibited greater photodegradation ability toward MB dyes. In addition, the NST showed high gas-sensing responses compared with the NPT when exposed to acetone vapor. This result was attributable to the higher number of oxygen-deficient regions on the surfaces of the NST, which increased the amount of surface-chemisorbed oxygen species. This resulted in a relatively large resistance variation for the NST when exposed to acetone vapor.