Modulation of pore sizes of titanium dioxide photocatalysts by a facile template free hydrothermal synthesis method: implications for photocatalytic degradation of rhodamine B

Morphology-Dependent Photocatalytic Activity of Nanostructured Titanium Dioxide Coatings with Silver Nanoparticles

This study aims to improve the photocatalytic properties of titanium dioxide nanorods (TNRs) and other related nanostructures (dense nanorods, needle-like nanorods, nanoballs, and nanoflowers) by modifying them with silver nanoparticles (AgNPs). This preparation is carried out using a two-step method: sol-gel dip-coating deposition combined with hydrothermal crystal growth. Further modification with AgNPs was achieved through the photoreduction of Ag+ ions under UV illumination. The investigation explores the impact of different growth factors on the morphological development of TiO2 nanostructures by modulating (i) the chemical composition, the water:acid ratio, (ii) the precursor concentration involved in the hydrothermal process, and (iii) the duration of the hydrothermal reaction. Morphological characteristics, including the length, diameter, and nanorod density of the nanostructures, were analyzed using scanning electron microscope (SEM). The chemical states were determined through use of the X-ray photoelectron spectroscopy (XPS) technique, while phase composition and crystalline structure analysis was performed using the Grazing Incidence X-ray Diffraction (GIXRD) method. The results indicate that various nanostructures (dense nanorods, needle-like nanorods, nanoballs, and nanoflowers) can be obtained by modifying these parameters. The photocatalytic efficiency of these nanostructures and Ag-coated nanostructures was assessed by measuring the degradation of the organic dye rhodamine B (RhB) under both ultraviolet (UV) irradiation and visible light. The results clearly show that UV light causes the RhB solution to lose its color, whereas under visible light RhB changes into rhodamine 110, indicating a successful photocatalytic transformation. The nanoball-like structures' modification with the active metal silver (TNRs 4 Ag) exhibited high photocatalytic efficiency under both ultraviolet (UV) and visible light for different chemical composition parameters. The nanorod structure (TNRs 2 Ag) is more efficient under UV, but under visible-light photocatalyst, the TNRs 6 Ag (dense nanorods) sample is more effective.

Photocatalytic Tandem Protocol for the Synthesis of Bis(indolyl)methanes using Cu-g-C3N4-Imine Decorated on TiO2 Nanoparticles under Visible Light Irradiation

In this article, the visible-light-assisted photocatalytic activity of TiO2 nanoparticles functionalized with Cu(II) g-C3N4-imine was exploited for aerobic oxidation of alcohols to aldehydes followed by condensation with indoles in the presence of 2,2,6,6-tetramethylpiperidinyloxy to present a one-pot tandem strategy for the synthesis of bis(indolyl)methanes (BIMs) under solvent-free conditions. The synergistic effect between the components to improve the photocatalytic activity of the as-prepared Cu-g-C3N4-imine/TiO2 nanoparticles resulting from electron-hole separation was approved by PL spectroscopy. Moreover, action spectra showed a light-dependent photocatalysis with effective visible-light responsivity of the photocatalyst. The present method includes different aspects of green chemistry: one-pot tandem synthesis of a variety of BIMs using alcohols that are less toxic, more available, more economical, and more stable than aldehydes; removing the byproducts resulting from overoxidation of alcohols and polymerization of aldehydes and indoles; the use of air as a safe oxidant; visible light as a safe energy source; and solvent-free conditions. A reusability test demonstrated that the catalyst retained its efficiency even after five runs.

Wastewater Treatment Using High-Performance In Situ Formed Double-Heterojunction Janus Photocatalyst Microparticles Shaped via a Microfluidic Device

In this work, a heterogeneous photocatalysis system is fabricated for treating wastewater containing organic dyes and pharmaceutical substances. Double-heterojunction Janus photocatalysts are formed on the surface of size-tunable polydimethylsiloxane (PDMS) microparticles shaped via simple and low-cost coflow microfluidic devices. Ag0/Ag0-TiO2/TiO2 Janus-like photocatalysts are synthesized on the surface of porous PDMS microparticles as the support in which the metal-semiconductor heterojunction of Ag0/Ag0-TiO2 and the second heterojunction of Ag0-TiO2/TiO2 are created in situ, leading to the formation of Ag0/Ag0-TiO2/TiO2@PDMS photocatalysis systems. To form the heterojunctions on the PDMS surface, the polymer chain etching method is employed as a desired strategy to have half of the TiO2 nanoparticles on the surface of microparticles, which are treated by a Ag source. Using salt additives and the etching method, PDMS microparticles are made porous, providing more surface area for photoreactions. Surprisingly, the highest decomposition efficiencies of 94.4 and 91.1% are achieved for rhodamine B(RhB) and tetracycline (TC), respectively, under visible light for 60 min pH 11, a light source at a distance of 2 cm, 5 mM AgNO3, 10 wt % TiO2, 7 wt % NaCl, and 20 gm/L photocatalyst, which are conditions that result in the best performance for RhB degradation. Regarding the stability of the photocatalysts, no significant change is observed in the performance after five cycles.

Improved photocatalytic performance of TiO2/carbon photocatalysts: Role of carbon additive

A series of TiO2 - based photocatalysts have been prepared by the incorporation of 10 wt% of various carbon-based nanomaterials as modifying agents to titania. More specifically, commercial TiO2 P25 was modified through a wet impregnation approach with methanol with four different carbon nanostructures: single-walled carbon nanotubes (SWCNTs), partially reduced graphene oxide (prGO), graphite (GI), and graphitic carbon nitride (gCN). Characterization results (XPS and Raman) anticipate the occurrence of important interfacial phenomena, preferentially for samples TiO2/SWCNT and TiO2/prGO, with a binding energy displacement in the Ti 2p contribution of 1.35 eV and 1.54 eV, respectively. These findings could be associated with an improved electron-hole mobility at the carbon/oxide interface. Importantly, these two samples constitute the most promising photocatalysts for Rhodamine B (RhB) photodegradation, with nearly 100% conversion in less than 2 h. These promising results must be associated with intrinsic physicochemical changes at the formed heterojunction structure and the potential dual-role of the composites able to adsorb and degrade RhB simultaneously. Cyclability tests confirm the improved performance of the composites (e.g., TiO2/SWCNT, 100% degradation in 1 h) due to the combined adsorption/degradation ability, although the regeneration after several cycles is not complete due to partial blocking of the inner cavities in the carbon nanotubes by non-reacted RhB. Under these reaction conditions, Rhodamine-B xanthene dye degrades via the de-ethylation route.

Machine learning analysis to interpret the effect of the photocatalytic reaction rate constant (k) of semiconductor-based photocatalysts on dye removal

Photocatalytic reactions with semiconductor-based photocatalysts have been investigated extensively for application to wastewater treatment, especially dye degradation, yet the interactions between different process parameters have rarely been reported due to their complicated reaction mechanisms. Hence, this study aims to discern the impact of each factor, and each interaction between multiple factors on reaction rate constant (k) using a decision tree model. The dyes selected as target pollutants were indigo and malachite green, and 5 different semiconductor-based photocatalysts with 17 different compositions were tested, which generated 34 input features and 1527 data points. The Boruta Shapley Additive exPlanations (SHAP) feature selection for the 34 inputs found that 11 inputs were significantly important. The decision tree model exhibited for 11 input features with an R2 value of 0.94. The SHAP feature importance analysis suggested that photocatalytic experimental conditions, with an importance of 59%, was the most important input category, followed by atomic composition (39%) and physicochemical properties (2%). Additionally, the effects on k of the synergy between the metal cocatalysts and important experimental conditions were confirmed by two feature SHAP dependence plots, regardless of importance order. This work provides insight into the single and multiple factors that affect reaction rate and mechanism.

The degradation of bisphenol-A organic pollutant using the dispersal of TiO2 nanorods onto the partial reduction of graphene oxide nanosheets

The notion of innovative combinations of semiconducting metal oxides for photocatalytic destruction is a key factor in the removal of environmental contaminants. However, for the first time, the combination was made possible for the aforementioned reason by embedding one-dimensional titanium dioxide (TiO2) semiconductor nanorods on two-dimensional rGO (reduced graphene oxide) nanosheets utilizing hydrothermal and a modified Hummers' method. By applying several sophisticated procedures, the properties of these catalysts were found, and then the degradation of BPA (bisphenol-A) was examined with UV and visible light sources. Further, all the analyses were performed on pure TiO2 material. As a result of the synergistic interaction between TiO2 and rGO, the rGO-TiO2 catalyst produced a favorable photocatalytic outcome. The structural investigation of rGO-TiO2 has confirmed that the TiO2 was in anatase phase along with GO and rGO peaks, and the morphological characterization showed that the TiO2 nanorods were integrated randomly into the rGO nanosheets along with defective sites. Also, adding rGO to TiO2 causes charge separation, and π-π interactions to improve the visible light absorption range. In this study, the main model organic component in the photocatalytic degradation is bisphenol-A (BPA). During visible light irradiation, the OH radicals were finally produced by the redox reactions. Furthermore, the rGO surface adsorbs the phenol molecules due to graphene π-π interactions, thus narrowing the band gap and increasing the efficiency of BPA degradation.

Bismuth Tungstate Nanoplates-Vis Responsive Photocatalyst for Water Oxidation

The development of visible-light-responsive (VLR) semiconductor materials for effective water oxidation is significant for a sustainable and better future. Among various candidates, bismuth tungstate (Bi2WO6; BWO) has attracted extensive attention because of many advantages, including efficient light-absorption ability, appropriate redox properties (for O2 generation), adjustable morphology, low cost, and profitable chemical and optical characteristics. Accordingly, a facile solvothermal method has been proposed in this study to synthesize two-dimensional (2D) BWO nanoplates after considering the optimal preparation conditions (solvothermal reaction time: 10-40 h). To find the key factors of photocatalytic performance, various methods and techniques were used for samples' characterization, including XRD, FE-SEM, STEM, TEM, HRTEM, BET-specific surface area measurements, UV/vis DRS, and PL spectroscopy, and photocatalytic activity was examined for water oxidation under UV and/or visible-light (vis) irradiation. Famous commercial photocatalyst-P25 was used as a reference sample. It was found that BWO crystals grew anisotropically along the {001} basal plane to form nanoplates, and all properties were controlled simultaneously by tuning the synthesis time. Interestingly, the most active sample (under both UV and vis), prepared during the 30 h solvothermal reaction at 433 K (BWO-30), was characterized by the smallest specific surface area and the largest crystals. Accordingly, it is proposed that improved crystallinity (which hindered charge carriers' recombination, as confirmed by PL), efficient photoabsorption (using the smallest bandgap), and 2D mesoporous structure are responsible for the best photocatalytic performance of the BWO-30 sample. This report shows for the first time that 2D mesoporous BWO nanoplates might be successfully prepared through a facile template-free solvothermal approach. All the above-mentioned advantages suggest that nanostructured BWO is a prospective candidate for photocatalytic applications under natural solar irradiation.

Shaddock peel-derived N-doped carbon quantum dots coupled with ultrathin BiOBr square nanosheets with boosted visible light response for high-efficiency photodegradation of RhB

In the present work, we constructed a serials of novel shaddock peel-derived N-doped carbon quantum dots (NCQDs) coupled with BiOBr composites. The result showed that the as-synthesized BiOBr (BOB) was composed of ultrathin square nanosheets and flower-like structure, and NCQDs were uniformly dispersed on the surface of BiOBr. Furthermore, the BOB@NCQDs-5 with optimal NCQDs content displayed the top-flight photodegradation efficiency with ca. 99% of removal rate within 20 min under visible light and possessed excellent recyclability and photostability after 5 cycles. The reason was attributed to relatively large BET surface area, the narrow energy gap, inhibited recombination of charge carriers and excellent photoelectrochemical performances. Meanwhile, the improved photodegradation mechanism and possible reaction pathways were also elucidated in detail. On this basis, the study opens a novel perspective to obtain a highly efficient photocatalyst for practical environment remediation.

Nanohybrid catalysts with porous structures for environmental remediation through photocatalytic degradation of emerging pollutants

Water supplies have been seriously challenged by new emerging pollutants, which are difficult to remove by traditional wastewater treatment. Thus, new technologies such as catalytic advanced oxidation processes have merged as suitable solutions; however, the drawbacks of typical catalysts limit their application. To overcome this issue, new materials with enhanced textural properties have been developed, showing that their porosity and chemical nature influence their potential as a catalyst. Herein, the recent progress in highly porous catalysts and their suitable deployment to effectively nano-remediate the polluted environmental matrices are reviewed in detail. First, following a brief introduction, several environmental pollutants of emerging concerns from different sectors, including pharmaceutical residues, endocrine-disrupting chemicals (EDCs), pesticides, and hazardous dyes are also introduced with relevant examples. To effectively tackle the sustainable remediation of emerging pollutants, this work also focuses on the multifunctional features of nanohybrid porous materials that act as catalysts constructs to degrade emerging pollutants. The influence of surface reactive centers, stability, bandgap energies, light absorption capacities, and pollutants adsorption capacities are also discussed. Successful examples of the employment of nanohybrid porous catalysts for the degradation of pharmaceutical pollutants, EDCs, pesticides, and hazardous dyes are summarized. Finally, some challenges faced by nanohybrid porous materials to achieve their potential application as advanced catalysts for environmental remediation have been identified and presented herein.

Modulation of photocatalytic properties through counter-ion substitution: tuning the bandgaps of aromatic sulfonium octamolybdates for efficient photo-degradation of rhodamine B

Modulating the photocatalytic properties of polyoxometalate-organic hybrids through counterion substitution is a less explored concept. In this study, a new series of aromatic sulfonium counterions (ASCs) having the general formula X-C₆H₄-S(Me₂)⁺, where X represents different functional substituents such as -H, -Cl, -Me, and -CHO at the para-position of the sulfonium moiety on a benzene ring, have been used for fine-tuning the optical bandgaps and adsorption properties of octamolybdate [Mo₈O₂₆]^4- hybrids for photocatalytic dye degradation applications. The photodegradation of rhodamine B (RhB) is used as a model reaction, which follows pseudo-first-order kinetics exhibiting counterion-dependent degradation rate constants. The hybrid catalyst bearing a -CHO substituent on the ASC showed the lowest bandgap (2.91 eV) and the highest degradation rate constant (0.0141 min^-1) of the series. A possible mechanism of photocatalytic dye degradation by hybrids involving the generation of reactive oxygen species (ROS) has been proposed, supported by radical scavenging studies. The intermediates formed during the photodegradation of RhB were analyzed and identified using electrospray ionization mass spectrometry (ESI-MS). The present study reveals a new strategy for tuning the photocatalytic properties of hybrids using differently functionalized ASCs and opens up new avenues for novel POM-hybrids as potential photocatalysts for environmental remediation applications.

Ti-Based porous materials for reactive oxygen species-mediated photocatalytic reactions

Reactive oxygen species (ROS) are highly reactive oxidants that are typically generated by the irradiation of semiconducting materials with visible or UV light and are widely used for the photocatalytic degradation of toxic substances, photodynamic therapy, and selective organic transformations. In this context, TiO2 is considered to be among the most promising photocatalysts due to its high redox activity, structural stability, and natural abundance. In view of the extensive development of highly active photocatalysts, we herein briefly introduce TiO2 and the mechanisms of TiO2-mediated ROS generation, subsequently focusing on key advances in the design and synthesis of Ti-containing porous materials, such as porous TiO2, Ti-based metal-organic frameworks, and Ti-based metal-organic aerogels. In particular, this review highlights the significance of porosity and the structure-function relationship for the development of Ti-based photocatalysts. The structures, porosities, and ROS generation mechanisms of these materials as well as the related efficiencies of ROS-mediated photocatalytic organic transformations are discussed in detail to provide a useful reference for future researchers and to inspire the exploration of high-performance photocatalysts.

SnS2/TiO2 Nanocomposites for Hydrogen Production and Photodegradation under Extended Solar Irradiation

Earth–abundant transition metal chalcogenide materials are of great research interest for energy production and environmental remediation, as they exhibit better photocatalytic activity due to their suitable electronic and optical properties. This study focuses on the photocatalytic activity of flower-like SnS2 nanoparticles (composed of nanosheet subunits) embedded in TiO2 synthesized by a facile hydrothermal method. The materials were characterized using different techniques, and their photocatalytic activity was assessed for hydrogen evolution reaction and the degradation of methylene blue. Among the catalysts studied, 10 wt. % of SnS2 loaded TiO2 nanocomposite shows an optimum hydrogen evolution rate of 195.55 µmolg−1, whereas 15 wt. % loading of SnS2 on TiO2 exhibits better performance against the degradation of methylene blue (MB) with the rate constant of 4.415 × 10−4 s−1 under solar simulated irradiation. The improved performance of these materials can be attributed to the effective photo-induced charge transfer and reduced recombination, which make these nanocomposite materials promising candidates for the development of high-performance next-generation photocatalyst materials. Further, scavenging experiments were carried out to confirm the reactive oxygen species (ROS) involved in the photocatalytic degradation. It can be observed that there was a 78% reduction in the rate of degradation when IPA was used as the scavenger, whereas around 95% reduction was attained while N2 was used as the scavenger. Notably, very low degradation (<5%) was attained when the dye alone was directly under solar irradiation. These results further validate that the •OH radical and the superoxide radicals can be acknowledged for the degradation mechanism of MB, and the enhancement of degradation efficiency may be due to the combined effect of in situ dye sensitization during the catalysis and the impregnation of low bandgap materials on TiO2.

Survival assessment of simple food webs for dye wastewater after photocatalytic degradation using SnO2/GO nanocomposites under sunlight irradiation

The release of textile effluent into the natural waters poses a serious threat to the aquatic ecosystem. Here, SnO₂/GO nanocomposites were synthesized with tunable morphology by the addition of GO with a sonochemical method. The material was characterized using X-ray Diffraction (XRD), scanning electronic microscopy (SEM), Ultraviolet-visible spectroscopy (UV-vis), and infrared spectrometry (IR). The photocatalytic degradation of Rhodamine B (RhB) and textile dye wastewater (TDW) using SnO₂/GO nanocomposites was studied under sunlight irradiation. The SnO₂/GO nanocomposites exhibited high photocatalytic activity towards the degradation of RhB and TDW with up to 95% removal efficiency. The catalyst dosage, concentration variation, and reusability of the catalyst were also examined to optimize the reaction conditions for the degradation of dye. Bioassays were used to investigate the survival growth rate of simple food webs such as Chlorella pyrenoidosa (CP), Artemia salina (AS) and Danio rerio (DR) in the treated and untreated solution. These simple food web model animals showed good reliability for analyzing the toxicity of the treated and untreated wastewater. Further, histology was analyzed to find out the influence of the dye solution in the animal model. These results suggest that the SnO₂/GO nanocomposite shows promising efficiency in the wastewater treatment, which is further confirmed in the toxicity analysis.

Iron Magnetic Nanoparticle-Induced ROS Generation from Catechol-Containing Microgel for Environmental and Biomedical Applications

Reactive oxygen species (ROS) can degrade organic compounds and function as a broad-spectrum disinfectant. Here, dopamine methacrylamide (DMA) was used to prepare catechol-containing microgels, which can release ROS via metal-catechol interaction. A combination of the microgel and iron magnetic nanoparticle (FeMNP) significantly reduced the concentration of four organic dyes (Alizarin Red S, Rhodamine B, Crystal Violet, and Malachite Green) and an antibiotic drug, ciprofloxacin, dissolved in solution. Degradation of dye occurred across a wide range of pH levels (pH 3-9). This simple combination was also antimicrobial against both Escherichia coli and Staphylococcus aureus. Electron paramagnetic resonance spectroscopy (EPR) results indicate that singlet oxygen was generated during the reaction between catechol and FeMNP at both pH 3 and 7.4, which was responsible for the degradation of organic compounds and bactericidal features of the microgel. Unlike autoxidation that only occurs at a neutral to basic pH, FeMNP-induced catechol oxidation generated singlet oxygen over a wide range of pH level. Additionally, catechol chelates heavy metal ions, resulting in their removal from solution and repurposed these metal ions for dye degradation. This multifunctional microgel can potentially be used for environmental applications for the removal of organic pollutants and heavy metal ions from wastewater, as well as reducing bacterial infection in biomedical applications.

Catalytic Decolorization of Rhodamine B, Congo Red, and Crystal Violet Dyes, with a Novel Niobium Oxide Anchored Molybdenum (Nb–O–Mo)

In this work, a new metal-to-metal charge transfer (MMCT) heterogeneous catalyst (Nb–O–Mo) was synthesized by a chemical grafting method under an inert atmosphere. The activity of the covalently anchored oxo-bridged Nb–O–Mo catalyst was estimated for decolorization of Rh B, congo red, and crystal violet dyes in an aqueous solution under fluorescent light. The catalyst was characterized via X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometer, Fourier-transform infrared, and FT-Raman. The catalytic decolorization was evaluated from the UV spectra of dyes in aqueous solution by changing different factors, including dye concentration, temperature, and catalyst loading. Decolorization percentages were 83%–89%, 86%–95%, 97%–99% for Rh B, Congo Red and Crystal Violet in 1 min at 298 K, showing the best performance among other catalysts. Decolorization efficiency for 50 ppm of Rh B was improved from 92% to 98%, with a temperature increase to 318 K.

Mesoporous Titanium Dioxide: Synthesis and Applications in Photocatalysis, Energy and Biology

Mesoporous materials are materials with high surface area and intrinsic porosity, and therefore have attracted great research interest due to these unique structures. Mesoporous titanium dioxide (TiO₂) is one of the most widely studied mesoporous materials given its special characters and enormous applications. In this article, we highlight the significant work on mesoporous TiO₂ including syntheses and applications, particularly in the field of photocatalysis, energy and biology. Different synthesis methods of mesoporous TiO₂-including sol⁻gel, hydrothermal, solvothermal method, and other template methods-are covered and compared. The applications in photocatalysis, new energy batteries and in biological fields are demonstrated. New research directions and significant challenges of mesoporous TiO₂ are also discussed.

Advanced catalytic performance of amorphous MoS2 for degradation/reduction of organic pollutants in both individual and simultaneous fashion

A cluster [(S₂)₂Mo(S₂)₂Mo(S₂)₂], has been used to synthesise molybdenum sulfide microparticles (MPs) by solvothermal treatments under inert environment. During synthesis, surfactants i.e. oleylamine and dodecanthiol take part in chief role in shaping the morphology of MPs into ultrathin nano-fibre, and nano-rod. MPs have been characterized by X-ray diffraction analysis, energy dispersive X-ray spectroscopy, transmission electron microscopy and UV-vis spectroscopic techniques. The optical spectral data reveals a simultaneous presence of direct and indirect band gap in both MoS₂. The material emerges as an effective catalyst towards the mineralization of different cationic dyes (rhodamine B and methylene blue) and anionic dye (rosebngal). These MPs have also been effectively used for the simultaneous degradations of different dyes in the same reaction mixture which make further highlighted the catalytic performances of MoS₂. The above kinetics of the decomposition processes were examined and found to follow the pseudo-first-order reaction model. The plausible mechanism has been explained by comparing the position of conduction band levels of MoS₂ (measured by Mott-schotky and touc's plot) and potential value of borohydride. We have also investigated the active species behind the degradation of dyes by using different scavengers. The new catalyst was also effective for the degradation of mixture of dyes to the same extent as it was in case of individual.

One-Dimensional-Like Titania/4'-Pentyl-4-Biphenylcarbonitrile Composite Synthesized Under Magnetic Field and its Structure-Photocatalytic Activity Relationship

The demonstration of the structure-properties relationship of shape-dependent photocatalysts remains a challenge today. Herein, one-dimensional (1-D)-like titania (TiO₂), as a model photocatalyst, has been synthesized under a strong magnetic field in the presence of a magnetically responsive liquid crystal as the structure-aligning agent to demonstrate the relationship between a well-aligned structure and its photocatalytic properties. The importance of the 1-D-like TiO₂ and its relationship with the electronic structures that affect the electron-hole recombination and the photocatalytic activity need to be clarified. The synthesis of 1-D-like TiO₂ with liquid crystal as the structure-aligning agent was carried out using the sol-gel method under a magnetic field (0.3 T). The mixture of liquid crystal, 4'-pentyl-4-biphenylcarbonitrile (5CB), tetra-n-butyl orthotitanate (TBOT), 2-propanol, and water, was subjected to slow hydrolysis under a magnetic field. The TiO₂-5CB took a well-aligned whiskerlike shape when the reaction mixture was placed under the magnetic field, while irregularly shaped TiO₂-5CB particles were formed when no magnetic field was applied. It shows that the strong interaction between 5CB and TBOT during the hydrolysis process under a magnetic field controls the shape of titania. The intensity of the emission peaks in the photoluminescence spectrum of 1-D-like TiO₂-5CB was lowered compared with the TiO₂-5CB synthesized without the magnetic field, suggesting the occurrence of electron transfer from 5CB to the 1-D-like TiO₂-5CB during ultraviolet irradiation. Apart from that, direct current electrical conductivity and Hall effect studies showed that the 1-D-like TiO₂ composite enhanced electron mobility. Thus, the recombination of electrons and holes was delayed due to the increase in electron mobility; hence, the photocatalytic activity of the 1-D-like TiO₂ composite in the oxidation of styrene in the presence of aqueous hydrogen peroxide under UV irradiation was enhanced. This suggests that the 1-D-like shape of TiO₂ composite plays an important role in its photocatalytic activity.

New insight into the selective photocatalytic oxidation of RhB through a strategy of modulating radical generation

Rhodamine B (RhB) has often been used as a model pollutant, but its photocatalytic mechanism is still controversial. Herein, Ag NPs were sandwiched between CdS QDs and amorphous-TiO2 (a-TiO2) with the intent to build a CdS/Ag/a-TiO2 catalyst with highly selective oxidation activity. When rhodamine B (RhB) was used as the model organic compound, the CdS/Ag/a-TiO2 composite can not only modulate radical generation but also improve the conversion ratio of RhB to rhodamine 110 (Rh-110) to as high as 82% at 80 min during the visible-light irradiation. A series of the radical scavenging experiments revealed that CdS/Ag/a-TiO2 composites could modulate the effects of hydroxyl radicals (·OH) and superoxide anion radicals (·O2 -) at different reaction stages so that the overoxidation of RhB and Rh-110 were repressed. Therefore, the transient state protection mechanism of selective oxidation of RhB was proposed to explain the reaction selectivity for Rh-110. Although the effects of both ·O2 - and ·OH are important during the photocatalytic selective oxidation of RhB, it is shown that the selective oxidation of RhB would be performed when the effect of ·O2 - is bigger than the ·OH, if not, RhB would be oxidized unselectively. Meanwhile, this may provide a new strategy for modulating radical generation in the photocatalysis of water phases.

The diagnosis of hepatic fibrosis by magnetic resonance and near-infrared imaging using dual-modality nanoparticles

Hepatic fibrosis (HF), as the only reversible process of chronic liver disease, remains a big diagnostic challenge. Development of noninvasive and effective methods to assess quantitatively early-stage HF is of great clinical importance. Compared with conventional diagnostic methods, near-infrared fluorescence imaging (NIR) and magnetic resonance imaging (MRI) could offer highly sensitive and spatial resolution signals for HF detection. However, precise detection using contrast agents is not possible. Superparamagnetic iron oxide (SPIO) nanoparticles have low toxicity, high sensitivity and excellent biocompatibility. Integration of Fe₃O₄ nanoparticles and indocyanine green (ICG), coupled with targeting ligand of integrin α_vβ₃, arginine–glycine–aspartic acid (RGD) expressed on hepatic stellate cells (HSCs), were used to detect HF. Both in vivo and in vitro results showed that the SPIO@SiO₂–ICG–RGD had high stability and low cytotoxicity. The biodistribution of SPIO@SiO₂–ICG–RGD was significantly different between mice with HF and healthy controls. SPIO@SiO₂–ICG–RGD was characterized and the results of imaging in vitro and in vivo demonstrated the expression of integrin α_vβ₃ on activated HSCs. These data suggest that our SPIO@SiO₂–ICG–RGD probe could be used for the diagnosis of early-stage HF. This new nanoprobe with a dual-modality imaging approach holds great potential for the diagnosis and classification of HF.

Schematic diagram for the synthesis of SPIO@SiO₂–ICG–RGD.

3D macroporous TiO2inverse opal binary and ternary composite materials and their photocatalytic activity

We have fabricated binary and ternary 3D macroporous composite materials containing inverse opal TiO₂, gold nanoparticles and nanosized cadmium sulfide on glass slides and these materials show excellent photocatalytic activity.

UV-visible and near-infrared active NaGdF4:Yb:Er/Ag/TiO2 nanocomposite for enhanced photocatalytic applications

A near infra-red (NIR) active NaGdF₄:Yb:Er/Ag/TiO₂ nanocomposite photocatalyst was successfully synthesized by a one-pot thermal decomposition method.

Nanocasting of Periodic Mesoporous Materials as an Effective Strategy to Prepare Mixed Phases of Titania

Mesoporous titanium dioxide materials were prepared using a nanocasting technique involving silica SBA-15 as the hard-template. At an optimal loading of titanium precursor, the hexagonal periodic array of pores in SBA-15 was retained. The phases of titanium dioxide could be easily varied by the number of impregnation cycles and the nature of titanium alkoxide employed. Low number of impregnation cycles produced mixed phases of anatase and TiO₂(B). The mesoporous TiO₂ materials were tested for solar hydrogen production, and the material consisting of 98% anatase and 2% TiO₂(B) exhibited the highest yield of hydrogen from the photocatalytic splitting of water. The periodicity of the pores was an important factor that influenced the photocatalytic activity. This study indicates that mixed phases of titania containing ordered array of pores can be prepared by using the nanocasting strategy.

Ni2+ and Ti3+ co-doped porous black anatase TiO2 with unprecedented-high visible-light-driven photocatalytic degradation performance

A black Ni doped porous TiO₂ were fabricated via an in situ solid-state chemical reduction approach, which exhibited excellent visible-light-driven performance.

A controlled solvothermal synthesis of CuS hierarchical structures and their natural-light-induced photocatalytic properties

A solvothermal synthesis of CuS hierarchical structures for the photodegradation of methylene blue (MB).