Large scale synthesis and gas-sensing properties of anatase TiO2 three-dimensional hierarchical nanostructures

Improved Ethanol Sensing Performance of α-MnO2 Nanorods at Room Temperature Enabled through PPy Embedding

Ethanol is a colorless, highly flammable, volatile organic compound and is a biomarker for fatty liver diseases. So, high-performance and reliable ethanol sensors are the need of the day for biomedical and environmental monitoring applications and drunken driving detection. In this work, we have reported a polypyrrole (PPy)-embedded α-MnO2 nanorod (NR)-based chemiresistive sensor for the selective detection of trace ethanol vapor at room temperature (25 °C). PPy-embedded α-MnO2 NR nanocomposites (MP25, MP50, and MP100) were synthesized by in situ chemical oxidative polymerization of pyrrole followed by mixing of α-MnO2 NR having different weight ratios. The prepared nanocomposites were characterized by various sophisticated instruments such as XRD, FTIR, Raman spectroscopy, BET, FESEM, TEM, EDX, UV-vis spectroscopy, and current-voltage (I-V) measurement. The as-prepared sensor, namely, PPy-embedded α-MnO2 nanorod (MP50), shows the highest response to ethanol vapor with a detection lower limit of 1 ppm at room temperature with rapid response (∼2.39 s) and recovery (∼37.08 s) times associated with at least 60 days stability, excellent selectivity, good repeatability, and reproducibility. The formation of a p-n heterojunction and transfer of charge carriers between PPy and MnO2 nanoparticles are attributed to the enhancement of sensing performance. Thus, the prepared sensor could be potentially applicable to detect ethanol content in alcoholic beverages, diagnose liver disease from exhale breath analysis, and drunken driving detection.

TiO2 nanoflower photocatalysts: Synthesis, modifications and applications in wastewater treatment for removal of emerging organic pollutants

Titanium dioxide (TiO₂) has been considered as one of the most promising photocatalysts nanomaterials and is being used in a variety of fields of energy and environment under sunlight irradiation via photocatalysis. Highly efficient photocatalytic materials require the design of the proper structure with excellent morphology, interfacial structures, optical and surface properties, etc. Which are the key points to realize effective light-harvesting for photocatalytic applications. Hierarchical TiO₂ based nanoflower structures (i.e., 3D nanostructures) possess such characteristics and have attracted much attention in recent years. The uniqueness of TiO₂ nanoflowers (NFs) with a coarse texture and arranged structures demonstrates higher photocatalytic activity. This review deals with the hydrothermal synthesis of 3D TiO₂ NFs and effect of shape/size as well as various key synthesis parameters to improve their optoelectronic and photocatalytic properties. Furthermore, to improve their photocatalytic properties, various strategies such as doping engineering and heterojunction/nanocomposite formation with other functional nanomaterials have been discussed followed by their potential applications in photocatalytic degradation of various emerging pollutants discharged into the wastewater from various sources. Importance of such 3D nanoarchitecutres and future research in other fields of current interest in environments are discussed.

Gas Sensors Based on Titanium Oxides (Review)

Nanostructured titanium compounds have recently been applied in the design of gas sensors. Among titanium compounds, titanium oxides (TiO2) are the most frequently used in gas sensing devices. Therefore, in this review, we are paying significant attention to the variety of allotropic modifications of titanium oxides, which include anatase, rutile, brukite. Very recently, the applicability of non-stoichiometric titanium oxide (TiO2−x)-based layers for the design of gas sensors was demonstrated. For this reason, in this review, we are addressing some research related to the formation of non-stoichiometric titanium oxide (TiO2−x) and Magnéli phase (TinO2n−1)-based layers suitable for sensor design. The most promising titanium compounds and hetero- and nano-structures based on these compounds are discussed. It is also outlined that during the past decade, many new strategies for the synthesis of TiO2 and conducting polymer-based composite materials were developed, which have found some specific application areas. Therefore, in this review, we are highlighting how specific formation methods, which can be used for the formation of TiO2 and conducting polymer composites, can be applied to tune composite characteristics that are leading towards advanced applications in these specific technological fields. The possibility to tune the sensitivity and selectivity of titanium compound-based sensing layers is addressed. In this review, some other recent reviews related to the development of sensors based on titanium oxides are overviewed. Some designs of titanium-based nanomaterials used for the development of sensors are outlined.

Ethanol-sensing properties of cobalt porphyrin-functionalized titanium dioxide nanoparticles as chemiresistive materials that are integrated into a low power microheater

Gaseous ethanol detection has attracted significant interest owing to its practical applications such as in breath analysis, chemical process monitoring, and safety evaluations of food packaging. In this study, titanium dioxide (TiO2) nanoparticles functionalized with cobalt porphyrin (CoPP) are utilized as resistive ethanol-sensing materials, and are integrated with a suspended micro-heater for low power consumption. The micro-heater with the suspended structure inhibits substrate heat transfer, resulting in power consumption as low as 18 mW when the operating temperature is approximately 300 °C. CoPP functionalization allows an enhanced response (197.8%) to 10 ppm ethanol compared to that of pristine TiO2 nanoparticles. It is confirmed that the sensor response is reliable upon exposure to 10 ppm ethanol for three cycles. In addition, responses of different magnitude are obtained under exposure to ethanol at various concentrations from 9 to 1 ppm, indicating that the resistance change originates from a charge transfer between the sensing materials and target gas. The sensing mechanism of CoPP-functionalized TiO2 in relation to charge transfer is analyzed, and the performance of the proposed sensor with previously reported TiO2-based ethanol sensors is compared. Considering that it is processed by batch fabrication, consumes low power, and offers high sensitivity, the proposed sensor is promising for use as a portable sensor in the distributed monitoring of gaseous ethanol.

Tabrizi B, D’Elia V, Del Gobbo S, Jabbour GE. Microwave-Assisted Non-aqueous and Low-Temperature Synthesis of Titania and Niobium-Doped Titania Nanocrystals and Their Application in Halide Perovskite Solar Cells as Electron Transport Layers

Undoped and Nb-doped TiO2 nanocrystals are prepared by a microwave-assisted non-aqueous sol-gel method based on a slow alkyl chloride elimination reaction between metal chlorides and benzyl alcohol. Sub-4 nm nanoparticles are grown under microwave irradiation at 80 °C in only 3 h with precise control of growth parameters and yield. The obtained nanocrystals could be conveniently used to cast compact TiO2 or Nb-doped TiO2 electron transport layers for application in formamidinium lead iodide-based photovoltaic devices. Niobium doping is found to improve the cell performance by increasing the conductivity and mobility of the electron transport layer. At the same time, a measurable decrease in parasitic light absorption in the low wavelength portion of the spectrum was observed.

d-Glucose Adsorption on the TiO2 Anatase (100) Surface: A Direct Comparison Between Cluster-Based and Periodic Approaches

Titanium dioxide (TiO2) has been extensively studied as a suitable material for a wide range of fields including catalysis and sensing. For example, TiO2-based nanoparticles are active in the catalytic conversion of glucose into value-added chemicals, while the good biocompatibility of titania allows for its application in innovative biosensing devices for glucose detection. A key process for efficient and selective biosensors and catalysts is the interaction and binding mode between the analyte and the sensor/catalyst surface. The relevant features regard both the molecular recognition event and its effects on the nanoparticle electronic structure. In this work, we address both these features by combining two first-principles methods based on periodic boundary conditions and cluster approaches (CAs). While the former allows for the investigation of extended materials and surfaces, CAs focus only on a local region of the surface but allow for using hybrid functionals with low computational cost, leading to a highly accurate description of electronic properties. Moreover, the CA is suitable for the study of reaction mechanisms and charged systems, which can be cumbersome with PBC. Here, a direct and detailed comparison of the two computational methodologies is applied for the investigation of d-glucose on the TiO2 (100) anatase surface. As an alternative to the commonly used PBC calculations, the CA is successfully exploited to characterize the formation of surface and subsurface oxygen vacancies and to determine their decisive role in d-glucose adsorption. The results of such direct comparison allow for the selection of an efficient, finite-size structural model that is suitable for future investigations of biosensor electrocatalytic processes and biomass conversion catalysis.

Branching TiO2nanowire arrays for enhanced ethanol sensing

Nanostructure modulation is effective to achieve high performance TiO₂-based gas sensors. We herein report a wet-chemistry route to precipitate directly branched TiO₂nanowire arrays on alumina tubes for gas sensing applications. The optimized branched TiO₂nanowire array exhibits a response of 9.2 towards 100 ppm ethanol; whilst those of the pristine TiO₂nanowire array and the branched TiO₂nanowire powders randomly distributed are 5.1 and 3.1, respectively. The enhanced response is mainly contributed to the unique porous architecture and quasi-aligned nanostructure, which provide more active sites and also favor gas migration. Phase junctions between the backbone and the branch of the branched TiO₂nanowire arrays help the resistance modulation as a result of potential barriers. The facile precipitation of quasi-aligned arrays of branched TiO₂nanowires, which arein situgrown on ceramic tubes, thus provides a new economical synthetic route to TiO₂-based sensors with excellent properties.

Highly crystalline anatase TiO2 nanocuboids as an efficient photocatalyst for hydrogen generation

Highly crystalline anatase titanium dioxide (TiO2) nanocuboids were synthesized via a hydrothermal method using ethylenediamine tetraacetic acid as a capping agent. The structural study revealed the nanocrystalline nature of anatase TiO2 nanocuboids. Morphological study indicates the formation of cuboid shaped particles with thickness of ∼5 nm and size in the range of 10-40 nm. The UV-visible absorbance spectra of TiO2 nanocuboids showed a broad absorption with a tail in the visible-light region which is attributed to the incorporation of nitrogen atoms into the interstitial positions of the TiO2 lattice as well as the formation of carbonaceous and carbonate species on the surface of TiO2 nanocuboids. The specific surface areas of prepared TiO2 nanocuboids were found to be in the range of 85.7-122.9 m2 g-1. The formation mechanism of the TiO2 nanocuboids has also been investigated. Furthermore, the photocatalytic activities of the as-prepared TiO2 nanocuboids were evaluated for H2 generation via water splitting under UV-vis light irradiation and compared with the commercial anatase TiO2. TiO2 nanocuboids obtained at 200 °C after 48 h exhibited higher photocatalytic activity (3866.44 μmol h-1 g-1) than that of commercial anatase TiO2 (831.30 μmol h-1 g-1). The enhanced photoactivity of TiO2 nanocuboids may be due to the high specific surface area, good crystallinity, extended light absorption in the visible region and efficient charge separation.

Insights in the Application of Stoichiometric and Non-Stoichiometric Titanium Oxides for the Design of Sensors for the Determination of Gases and VOCs (TiO2-x and TinO2n-1 vs. TiO2)

In this review article, attention is paid towards the formation of various nanostructured stoichiometric titanium dioxide (TiO2), non-stoichiometric titanium oxide (TiO2-x) and Magnéli phase (TinO2n-1)-based layers, which are suitable for the application in gas and volatile organic compound (VOC) sensors. Some aspects related to variation of sensitivity and selectivity of titanium oxide-based sensors are critically overviewed and discussed. The most promising titanium oxide-based hetero- and nano-structures are outlined. Recent research and many recently available reviews on TiO2-based sensors and some TiO2 synthesis methods are discussed. Some promising directions for the development of TiO2-based sensors, especially those that are capable to operate at relatively low temperatures, are outlined. The applicability of non-stoichiometric titanium oxides in the development of gas and VOC sensors is foreseen and transitions between various titanium oxide states are discussed. The presence of non-stoichiometric titanium oxide and Magnéli phase (TinO2n-1)-based layers in 'self-heating' sensors is predicted, and the advantages and limitations of 'self-heating' gas and VOC sensors, based on TiO2 and TiO2-x/TiO2 heterostructures, are discussed.

SnO2/TiO2 Thin Film n-n Heterostructures of Improved Sensitivity to NO2

Thin-film n-n nanoheterostructures of SnO₂/TiO₂, highly sensitive to NO₂, were obtained in a two-step process: (i) magnetron sputtering, MS followed by (ii) Langmuir-Blodgett, L–B, technique. Thick (200 nm) SnO₂ base layers were deposited by MS and subsequently overcoated with a thin and discontinuous TiO₂ film by means of L–B. Rutile nanopowder spread over the ethanol/chloroform/water formed a suspension, which was used as a source in L–B method. The morphology, crystallographic and electronic properties of the prepared sensors were studied by scanning electron microscopy, SEM, X-ray diffraction, XRD in glancing incidence geometry, GID, X-ray photoemission spectroscopy, XPS, and uv-vis-nir spectrophotometry, respectively. It was found that amorphous SnO₂ films responded to relatively low concentrations of NO₂ of about 200 ppb. A change of more than two orders of magnitude in the electrical resistivity upon exposure to NO₂ was further enhanced in SnO₂/TiO₂ n-n nanoheterostructures. The best sensor responses R_NO2/R₀ were obtained at the lowest operating temperatures of about 120 °C, which is typical for nanomaterials. Response (recovery) times to 400 ppb NO₂ were determined as a function of the operating temperature and indicated a significant decrease from 62 (42) s at 123 °C to 12 (19) s at 385 °C A much smaller sensitivity to H₂ was observed, which might be advantageous for selective detection of nitrogen oxides. The influence of humidity on the NO₂ response was demonstrated to be significantly below 150 °C and systematically decreased upon increase in the operating temperature up to 400 °C.

Conductometric Response-Triggered Surface-Enhanced Raman Spectroscopy for Accurate Gas Recognition and Monitoring Based on Oxide-wrapped Metal Nanoparticles

Accurate and efficient gas monitoring is still a challenge because the existing sensing techniques mostly lack specific identification of gases or hardly meet the requirement of real-time readout. Herein, we present a strategy of conductometric response-triggered surface-enhanced Raman spectroscopy (SERS) for such gas monitoring, via designing and using ultrathin oxide-wrapped plasmonic metal nanoparticles (NPs). The oxide wrapping layer can interact with and capture target gaseous molecules and produce the conductometric response, while the plasmonic metal NPs possess strong SERS activity. In this strategy, the conductometric gas sensing is performed throughout the whole monitoring process, and once a conductometric response is generated, it will trigger SERS measurements, which can accurately recognize molecules and hence realize gas monitoring. The feasibility of this strategy has been demonstrated via using ultrathin SnO₂ layer-wrapped Au NP films to monitor gaseous 2-phenylethanethiol molecules. It has been shown that the monitoring is rapid, accurate, and quantifiable. There exist optimal values of working temperature and SnO₂ layer thickness, which are about 100 °C and 2.5 nm, respectively, for monitoring gaseous 2-phenylethanethiol. The monitoring signal intensity has a linear relation with the gas concentration in the range from 1 to 100 ppm on a logarithmic scale. Furthermore, the monitoring limits are at the ppm level for some typical gases, such as 2-phenylethanethiol, cyclohexanethiol, 1-dodecanethiol, and toluene. This study establishes the conductometric response-triggered SERS, which enables accurate gas recognition and real-time monitoring.

Mass Transport Determined Silica Nanowires Growth on Spherical Photonic Crystals with Nanostructure-Enabled Functionalities

A robust and facile method has been developed to obtain directional growth of silica nanowires (SiO₂ NWs) by regulating mass transport of silicon monoxide (SiO) vapor. SiO₂ NWs are grown by vapor-liquid-solid (VLS) process on a surface of gold-covered spherical photonic crystals (SPCs) annealed at high temperature in an inert gas atmosphere in the vicinity of a SiO source. The SPCs are prepared from droplet confined colloidal self-assembly. SiO₂ NW morphology is governed by diffusion-reaction process of SiO vapor, whereby directional growth of SiO₂ NWs toward the low SiO concentration is obtained at locations with a high SiO concentration gradient, while random growth is observed at locations with a low SiO concentration gradient. Growth of NWs parallel to the supporting substrate surface is of great importance for various applications, and this is the first demonstration of surface-parallel growth by controlling mass transport. This controllable NW morphology enables production of SPCs covered with a large number of NWs, showing multilevel micro-nano feature and high specific surface area for potential applications in superwetting surfaces, oil/water separation, microreactors, and scaffolds. In addition, the controllable photonic stop band properties of this hybrid structure of SPCs enable the potential applications in photocatalysis, sensing, and light harvesting.

Highly Sensitive Detection of Benzene, Toluene, and Xylene Based on CoPP-Functionalized TiO2 Nanoparticles with Low Power Consumption

Among various metal oxides, titanium dioxide (TiO₂) has received considerable interest as a gas-sensing material owing to its high reliability at high operating temperatures. Nonetheless, TiO₂ generally has low sensitivity to target gases. In particular, TiO₂-based sensors have difficulty in sensitively detecting benzene, toluene, and xylene (referred to as BTX). Moreover, the reported TiO₂-based sensors have not simultaneously satisfied the demand for tens of ppb BTX detection and operation with low power consumption. This work proposes a BTX sensor using cobalt porphyrin (CoPP)-functionalized TiO₂ nanoparticles as a sensing material on a suspended microheater fabricated by bulk micromachining for low power consumption. TiO₂ nanoparticles show an enhanced sensitivity (245%) to 10 ppm toluene with CoPP functionalization. The proposed sensor exhibits high sensitivity to BTX at concentrations ranging from 10 ppm down to several ppb. The high reliability of the sensor is also explored through the long-time operation with repeated exposure to 10 ppm toluene for 14 h.

Engineering of monodisperse core-shell up-conversion dendritic mesoporous silica nanocomposites with a tunable pore size

Fabricating lanthanide doped up-conversion luminescence based nanocomposites has drawn increasing attention in nanoscience and nanotechnology. Although challenging in precise synthesis, structure manipulation and interfacial engineering, fabricating dendritic mesoporous silica coated up-conversion nanoparticles (UCNP@dMSNs) with a tunable pore size is of great importance for the functionalization and application of UCNPs. Herein, we report a strategy to prepare uniform monodisperse UCNP@dMSNs with a core-shell structure. The silica shell has tunable center-radial and dendritic mesoporous channels. The synthesis was carried out in the heterogeneous oil-water microemulsion phase of the Winsor III system reaction system, which allows silica to be deposited directly on hydrophobic UCNPs through the self-anchoring of micelle complexes on the oleic acid ligand. The average pore size of UCNP@dMSNs could be tailored from ∼10 to ∼35 nm according to the varied amounts of co-solvent in the mixture. The microemulsion approach could also be used to prepare hierarchical UCNP@dMSNs with a multi-generational mesostructure. The resultant UCNP@dMSNs exhibit the unique advantage of loading "guest" nanoparticles in a self-absorption manner. We proved that Cu1.8S NPs (∼10 nm), Au NPs (∼10 nm) and Fe3O4 NPs (∼25 nm) could be incorporated in UCNP@dMSNs, which in turn validates the high adsorption capacity of UCNP@dMSNs.

TiO2-x/TiO2-Structure Based 'Self-Heated' Sensor for the Determination of Some Reducing Gases

In this research we report the gas-sensing properties of TiO2-x/TiO2-based hetero-structure, which was 'self-heated' by current that at constant potential passed through the structure. Amperometric measurements were applied for the evaluation of sensor response towards ethanol, methanol, n-propanol and acetone gases/vapours. The sensitivity towards these gases was based on electrical resistance changes, which were determined by amperometric measurements of current at fixed voltage applied between Pt-based contacts/electrodes deposited on the TiO2-x/TiO2-based layer. X-ray diffraction (XRD) analysis revealed the formation of TiO2-x/TiO2-based hetero-structure, which is mainly based on Ti3O5/TiO2 formed during the hydro-thermal oxidation-based sensing-layer preparation process. Additionally, photoluminescence and time-resolved photoluminescence decay kinetics-based signals of this sensing structure revealed the presence of TiO2 mainly in the anatase phase in the TiO2-x/TiO2-based hetero-structure, which was formed at 400 °C annealing temperature. The evaluation of TiO2-x/TiO2-based gas-sensing layer was performed at several different temperatures (25 °C, 72 °C, 150 °C, 180 °C) and at these temperatures different sensitivity to the aforementioned gaseous materials was determined.

High Energy Capacitors Based on All Metal-Organic Frameworks Derivatives and Solar-Charging Station Application

High energy and efficient solar charging stations using electrochemical capacitors (ECs) are a promising portable power source for the future. In this work, two kinds of metal-organic framework (MOF) derivatives, NiO/Co₃ O₄ microcubes and Fe₂ O₃ microleaves, are prepared via thermal treatment and assembled into electrochemical capacitors, which deliver a relatively high specific energy density of 46 Wh kg^-1 at 690 W kg^-1 . In addition, a solar-charging power system consisting of the electrochemical capacitors and monocrystalline silicon plates is fabricated and a motor fan or 25 LEDs for 5 and 30 min, respectively, is powered. This work not only adds two novel materials to the growing categories of MOF-derived advanced materials, but also successfully achieves an efficient solar-ECs system for the first time based on all MOF derivatives, which has a certain reference for developing efficient solar-charge systems.

Readily available titania nanostructuring routines based on mobility and polarity controlled phase separation of an amphiphilic diblock copolymer

The amphiphilic diblock copolymer polystyrene-block-polyethylene oxide is combined with sol-gel chemistry to control the structure formation of blade-coated foam-like titania thin films. The influence of evaporation time before immersion into a poor solvent bath and polarity of the poor solvent bath are studied. Resulting morphological changes are quantified by scanning electron microscopy (SEM) and grazing incidence small angle X-ray scattering (GISAXS) measurements. SEM images surface structures while GISAXS accesses inner film structures. Due to the correlation of evaporation time and mobility of the polymer template during the phase separation process, a decrease in the distances of neighboring titania nanostructures from 50 nm to 22 nm is achieved. Furthermore, through an increase of polarity of an immersion bath the energetic incompatibility of the hydrophobic block and the solvent can be enhanced, leading to an increase of titania nanostructure distances from 35 nm to 55 nm. Thus, a simple approach is presented to control titania nanostructure in foam-like films prepared via blade coating, which enables an easy upscaling of film preparation.

Ag Nanoparticles Located on Three-Dimensional Pine Tree-Like Hierarchical TiO2 Nanotube Array Films as High-Efficiency Plasmonic Photocatalysts

High specific surface area three-dimensional pine tree-like hierarchical TiO2 nanotube array films loaded with Ag nanoparticles were successfully prepared by one-step hydrothermal reaction combining with simple and feasible magnetron sputtering. The composite Ag/TiO2-branched nanotube arrays show outstanding photocatalytic property, which is attributed to the boost of plasmonic enhancement carrier generation and separation, higher specific surface area, higher organic pollutant absorption, faster charge transport, and superior light-harvesting efficiency for efficient charge collection. The work provides a cost-effective and flexible pathway to develop high-performance photocatalyst or optoelectronic devices.

Wet-Chemical Preparation of TiO₂-Based Composites with Different Morphologies and Photocatalytic Properties

TiO₂-based composites have been paid significant attention in the photocatalysis field. The size, crystallinity and nanomorphology of TiO₂ materials have an important effect on the photocatalytic efficiency. The synthesis and photocatalytic activity of TiO₂-based materials have been widely investigated in past decades. Based on our group’s research works on TiO₂ materials, this review introduces several methods for the fabrication of TiO₂, rare-earth-doped TiO₂ and noble-metal-decorated TiO₂ particles with different morphologies. We focused on the preparation and the formation mechanism of TiO₂-based materials with unique structures including spheres, hollow spheres, porous spheres, hollow porous spheres and urchin-like spheres. The photocatalytical activity of urchin-like TiO₂, noble metal nanoparticle-decorated 3D (three-dimensional) urchin-like TiO₂ and bimetallic core/shell nanoparticle-decorated urchin-like hierarchical TiO₂ are briefly discussed.

TiO₂-Based Nanoheterostructures for Promoting Gas Sensitivity Performance: Designs, Developments, and Prospects

Gas sensors based on titanium dioxide (TiO₂) have attracted much public attention during the past decades due to their excellent potential for applications in environmental pollution remediation, transportation industries, personal safety, biology, and medicine. Numerous efforts have therefore been devoted to improving the sensing performance of TiO₂. In those effects, the construct of nanoheterostructures is a promising tactic in gas sensing modification, which shows superior sensing performance to that of the single component-based sensors. In this review, we briefly summarize and highlight the development of TiO₂-based heterostructure gas sensing materials with diverse models, including semiconductor/semiconductor nanoheterostructures, noble metal/semiconductor nanoheterostructures, carbon-group-materials/semiconductor nano- heterostructures, and organic/inorganic nanoheterostructures, which have been investigated for effective enhancement of gas sensing properties through the increase of sensitivity, selectivity, and stability, decrease of optimal work temperature and response/recovery time, and minimization of detectable levels.

Synthesis of In2O3 nanoparticle/TiO2 nanobelt heterostructures for near room temperature ethanol sensing

The obtained In₂O₃ nanoparticle/TiO₂ nanobelt heterostructures exhibit a high sensitive toward ethanol at near room temperature of 45 °C and low detection limit of 1 ppm.

The controllable fabrication of a novel hierarchical nanosheet-assembled Bi2MoO6 hollow micronbox with ultra-high surface area for excellent solar to chemical energy conversion

In this study, we demonstrated that a novel controllable nano-sheet assembled Bi₂MoO₆ micronbox had higher activity for nitrogen fixation and dye degradation.

Non-fluorinated synthesis of anatase TiO2 with dominant {001} facets: influence of faceted structures on formaldehyde sensitivity

The extraordinary surface, electronic and catalytic properties of titanium dioxide (TiO₂) is better manifested with highly exposed {001} facets. This article illustrates the synthesis of {001} faceted TiO₂ nanosheets through a non-fluorinated route and oxidation of formaldehyde on the {001} facets using the synergistic effect of crystal facet, gold nanoparticle and UV irradiation.

Controlled synthesis and photocatalysis of sea urchin-like Fe3O4@TiO2@Ag nanocomposites

Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the core and nanofiber TiO2/Fe3O4/Ag nanoheterojunctions as the shell; and Ag nanoparticles with diameter of approximately 4 nm are loaded both on TiO2 nanofibers and inside the cavities of sea urchin-like Fe3O4@TiO2 nanocomposites uniformly. Ag nanoparticles lead to the production of more photogenerated charges in the TiO2/Fe3O4/Ag heterojunction via LSPR absorption, and enhance the band-gap absorption of TiO2, while the Fe3O4 cocatalyst provides the active sites for oxygen reduction by the effective transfer of photogenerated electrons to oxygen. So the photocatalytic performance is improved due to the synergistic effect of TiO2/Fe3O4/Ag nanoheterojunctions. As photocatalysts under UV and visible irradiation, the as-synthesized nanocomposites display enhanced photocatalytic and recycling properties for the degradation of ampicillin. Moreover, they present better broad-spectrum antibiosis under visible irradiation. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, makes this multifunctional nanostructure a promising candidate for antibiosis and remediation in aquatic environmental contamination in the future.

A 3D electrochemical immunodevice based on an Au paper electrode and using Au nanoflowers for amplification

A highly sensitive electrochemical immunosensor combined with a 3D origami device for detection of cancer antigen was developed based on a novel Au nanoparticle-modified paper working electrode.

Ni-doped rutile TiO2 nanoflowers: low-temperature solution synthesis and enhanced photocatalytic efficiency

A facile solution approach was developed to synthesize micrometre-sized aggregates of Ni-doped TiO₂ nanoflowers, which exhibited a rate constant four times that of commercial Degussa P25 TiO₂ nanoparticles under the UV + Vis illumination.

Synthesis of nanosphere TiO2 with flower-like micro-composition and its application for the selective catalytic reduction of NO with NH3 at low temperature

TiO₂ nanospheres consisting of flower-like nanopowders were synthesized by a solvothermal method, and Cu/TiO₂(T) catalysts were prepared via an impregnation method.

Enhanced Gas-Sensing Properties of the Hierarchical TiO₂ Hollow Microspheres with Exposed High-Energy {001} Crystal Facets

Anatase hierarchical TiO2 with innovative designs (hollow microspheres with exposed high-energy {001} crystal facets, hollow microspheres without {001} crystal facets, and solid microspheres without {001} crystal facets) were synthesized via a one-pot hydrothermal method and characterized. Based on these materials, gas sensors were fabricated and used for gas-sensing tests. It was found that the sensor based on hierarchical TiO2 hollow microspheres with exposed high-energy {001} crystal facets exhibited enhanced acetone sensing properties compared to the sensors based on the other two materials due to the exposing of high-energy {001} crystal facets and special hierarchical hollow structure. First-principle calculations were performed to illustrate the sensing mechanism, which suggested that the adsorption process of acetone molecule on TiO2 surface was spontaneous, and the adsorption on high-energy {001} crystal facets would be more stable than that on the normally exposed {101} crystal facets. Further characterization indicated that the {001} surface was highly reactive for the adsorption of active oxygen species, which was also responsible for the enhanced sensing performance. The present studies revealed the crystal-facets-dependent gas-sensing properties of TiO2 and provided a new insight into improving the gas sensing performance by designing hierarchical hollow structure with special-crystal-facets exposure.

TiO2 hybrid photocatalytic systems: impact of adsorption and photocatalytic performance

For the past 40 years, titanium dioxide (TiO2) nanomaterials have attracted immense attention because of their potential applications in the photodegradation of organic pollutants, photocatalytic water splitting for H2 generation, and dye-sensitized solar cells. Despite the fact that the potential applications of TiO2 nanoparticles are ubiquitous, they are not problem free, examples include a large interfacial area that causes slow charge carrier transport, a wide optical band gap that leads to limited applications using solar light, and single-phase and nanoscales features that induce fast recombination of photo-reduced carriers. Therefore, this review highlights the development associated with the adsorption photocatalysis hybrid system for treating wastewater. The immobilization of TiO2 photocatalysts in metal oxide, carbon, and ceramic materials to form TiO2 hybrid systems could prevent the problem of particle recovery, adsorption capacity, and the separation process. Such hybrid systems require significant effort of optimizing the specific surface area-to-volume ratio of the supported photocatalysts with its photocatalytic activities.

A self-assembled 3D Pt/TiO2 architecture for high-performance photocatalytic hydrogen production

A 3D Pt/TiO2 architecture assembled from 1D nanowires has been designed and successfully prepared by an environmentally-friendly one-pot solvothermal process. The formation mechanism has been investigated and the unique architecture exhibits an excellent photocatalytic hydrogen production rate as high as 13.33 mmol h(-1) g(-1), the corresponding apparent quantum efficiency reaches 34%.

Facile fabrication of heterostructured g-C3N4/Bi2MoO6 microspheres with highly efficient activity under visible light irradiation

A facile and template-free solvothermal method was developed for the synthesis of microspheric g-C₃N₄/Bi₂MoO₆ photocatalysts.

A 3D electrochemical immunodevice based on a porous Pt-paper electrode and metal ion functionalized flower-like Au nanoparticles

A 3D microfluidic paper-based electrochemical immunodevice (μ-PEID) for simultaneous sensitive detection of two tumor biomarkers was fabricated.