Oxygen atom transfer in the photocatalytic oxidation of alcohols by TiO2: oxygen isotope studies

Multifunctional polyoxometalates encapsulated in MIL-100(Fe): highly efficient photocatalysts for selective transformation under visible light

Multifunctional H₃PMo₁₂O₄₀ encapsulated in MIL-100(Fe) as dual functional visible-light-driven photocatalysts for selective transformation under visible light.

Carbon quantum dots and their applications

This review covers the progress in the research and development of carbon quantum dots and their applications in chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis.

Surface-mediated selective photocatalytic aerobic oxidation reactions on TiO2 nanofibres

The interaction between photocatalyst surface and the reactants may outweigh its light absorption ability in photocatalytic activities.

Enhanced photocatalytic activities of visible-light driven green synthesis in water and environmental remediation on Au/Bi2WO6 hybrid nanostructures

Deposition of Au NPs enhances photocatalytic activity toward selective oxidation of alcohol in water and Cr(vi) reduction over Bi₂WO₆ nanosheets.

Unraveling the photocatalytic mechanisms on TiO2 surfaces using the oxygen-18 isotopic label technique

During the last several decades TiO₂ photocatalytic oxidation using the molecular oxygen in air has emerged as a promising method for the degradation of recalcitrant organic pollutants and selective transformations of valuable organic chemicals. Despite extensive studies, the mechanisms of these photocatalytic reactions are still poorly understood due to their complexity. In this review, we will highlight how the oxygen-18 isotope labeling technique can be a powerful tool to elucidate complicated photocatalytic mechanisms taking place on the TiO₂ surface. To this end, the application of the oxygen-18 isotopic-labeling method to three representative photocatalytic reactions is discussed: (1) the photocatalytic hydroxylation of aromatics; (2) oxidative cleavage of aryl rings on the TiO₂ surface; and (3) photocatalytic decarboxylation of saturated carboxylic acids. The results show that the oxygen atoms of molecular oxygen can incorporate into the corresponding products in aqueous solution in all three of these reactions, but the detailed incorporation pathways are completely different in each case. For the hydroxylation process, the O atom in O₂ is shown to be incorporated through activation of O₂ by conduction band electrons. In the cleavage of aryl rings, O atoms are inserted into the aryl ring through the site-dependent coordination of reactants on the TiO₂ surface. A new pathway for the decarboxylation of saturated carboxylic acids with pyruvic acid as an intermediate is identified, and the O₂ is incorporated into the products through the further oxidation of pyruvic acid by active species from the activation of O₂ by conduction band electrons.

Visible-light driven oxidation of gaseous aliphatic alcohols to the corresponding carbonyls via TiO2 sensitized by a perylene derivative

Sensitized P25 TiO2 was prepared by wet impregnation with a home-prepared perylene dye, i.e., N,N'-bis(2-(1-piperazino)ethyl)-3,4,9,10-perylene-tetracarboxylic acid diimide dichloride (PZPER). Energy levels of PZPER were found to be compatible with those of TiO2 allowing fast electron transfer. The obtained catalyst has been characterized and used in the gas-phase partial oxidation of aliphatic primary and secondary alcohols, i.e., methanol, ethanol, and 2-propanol. The reaction was carried out under cut-off (λ > 400 nm) simulated solar radiation in O2 atmosphere. The perylene derivative allowed a good absorbance of visible radiation thanks to its low optical energy gap (2.6 eV) which was evaluated by cyclic voltammetry. The optimal organic sensitizing amount was found to be 5.6 % w/w in terms of yield in carbonyl derivatives. Moreover, no change in reactivity/selectivity was observed after 10-h irradiation thus confirming the catalyst stability. Yields into formaldehyde, acetaldehyde, and acetone were 67, 70, and 96 %, respectively. No significant amounts of organic byproducts were detected but for methanol oxidation, whereas a minor amount of the substrate degraded to CO2.

(Gold core)@(ceria shell) nanostructures for plasmon-enhanced catalytic reactions under visible light

Driving catalytic reactions with sunlight is an excellent example of sustainable chemistry. A prerequisite of solar-driven catalytic reactions is the development of photocatalysts with high solar-harvesting efficiencies and catalytic activities. Herein, we describe a general approach for uniformly coating ceria on monometallic and bimetallic nanocrystals through heterogeneous nucleation and growth. The method allows for control of the shape, size, and type of the metal core as well as the thickness of the ceria shell. The plasmon shifts of the Au@CeO2 nanostructures resulting from the switching between Ce(IV) and Ce(III) are observed. The selective oxidation of benzyl alcohol to benzaldehyde, one of the fundamental reactions for organic synthesis, performed under both broad-band and monochromatic light, demonstrates the visible-light-driven catalytic activity and reveals the synergistic effect on the enhanced catalysis of the Au@CeO2 nanostructures.

Determining the TiO2-photocatalytic aryl-ring-opening mechanism in aqueous solution using oxygen-18 labeled O2 and H2O

The molecules O2 and H2O dominate the cleavage of aromatic sp(2) C-C bonds, a crucial step in the degradation of aromatic pollutants in aqueous TiO2 photocatalysis, but their precise roles in this process have remained elusive. This can be attributed to the complex oxidative species involved and to a lack of available models for reactions with a high yield of direct products. Here, we used oxygen-18 isotope labeled O2 and H2O to observe the aromatic ring-opening reaction of the model compound 3,5-di-tert-butylcatechol (DTBC), which was mediated by TiO2 photocatalysis in an aqueous acetonitrile solution. By analyzing the primary intermediate products (∼75% yield), especially the seven-membered ring anhydrides that were formed, we obtained direct evidence for the oxygen atom of dioxygen insertion into a C-C bond of the aromatic ring. This indicates that molecular oxygen is the ultimate ring-opening agent in TiO2 photocatalysis and that it undergoes single O atom incorporation rather than the previously proposed molecular oxygen 1,2-addition processes. The ratio of intradiol to extradiol products depends on the particle size of TiO2 catalysts used, which suggests that the O2 activation is correlated with the available coordination sites on the TiO2 surface in the photocatalytic cleavage of the aromatic ring.

Selective photoredox using graphene-based composite photocatalysts

Graphene (GR) has proven to be a promising candidate to construct effective GR-based composite photocatalysts with enhanced catalytic activities for solar energy conversion. During the past few years, various GR-based composite photocatalysts have been developed and applied in a myriad of fields. In this perspective review, compared with the traditional applications of GR-based nanocomposites for the "non-selective" degradation of pollutants, photo-deactivation of bacteria and water splitting to H2 and O2, we mainly focus on the recent progress in the applications of GR-based composite photocatalysts for "selective" organic transformations, including reduction of CO2 to renewable fuels, reduction of nitroaromatic compounds to amino compounds, oxidation of alcohols to aldehydes and acids, epoxidation of alkenes, hydroxylation of phenol, and oxidation of tertiary amines. The different roles of GR in these GR-based nanocomposite photocatalysts such as providing a photoelectron reservoir and performing as an organic dye-like macromolecular photosensitizer have been summarized. In addition, graphene oxide (GO) as a co-catalyst in GO-organic species photocatalysts and GO itself as a photocatalyst for selective reduction of CO2 have also been demonstrated. Finally, perspectives on the future research direction of GR-based composite photocatalysts toward selective organic redox transformations are discussed and it is clear that there is a wide scope of opportunities awaiting us in this promising research field.

UV-assisted removal of inactive peroxide species for sustained epoxidation of cyclooctene on anatase TiO2

Epoxidation of olefins with H2O2 is one of the most important reactions in organic synthesis. We found that anatase TiO2 can be a good catalyst for the epoxidation of cyclooctene with H2O2 at room temperature. However, the catalyst deactivated quickly in the presence of excess amount of H2O2 because of the formation of inactive side-on Ti-η(2)-peroxide species on the surface of TiO2, the presence of which was confirmed by isotope-labelled resonance UV Raman spectroscopy and kinetics studies. Interestingly, the epoxidation reaction could be dramatically accelerated under irradiation of UV light with λ≥350 nm. This phenomenon is attributed to the photo-assisted removal of the inactive peroxide species, through which the active sites on the surface of anatase TiO2 are regenerated and the catalytic epoxidation of cyclooctene with H2O2 is resumed. This finding provides an alternative for sustained epoxidation reactions on TiO2 at room temperature. Moreover, it also has significant implications on the deactivation pathway and possible solutions in Ti-based heterogeneous catalysis or photocatalysis.

Selective aerobic oxidation mediated by TiO(2) photocatalysis

TiO2 is one of the most studied metal oxide photocatalysts and has unparal-leled efficiency and stability. This cheap, abundant, and non-toxic material has the potential to address future environmental and energy concerns. Understanding about the photoinduced interfacial redox events on TiO2 could have profound effect on the degradation of organic pollutants, splitting of H2O into H2 and O2, and selective redox organic transformations. Scientists traditionally accept that for a semiconductor photocatalyst such as TiO2 under the illumination of light with energy larger than its band gap, two photocarriers will be created to carry out their independent reduction and oxidation processes. However, our recent discoveries indicate that it is the concerted rather than independent effect of both photocarriers of valence band hole (hvb(+)) and conduction band electron (ecb(-)) that dictate the product formation during interfacial oxidation event mediated by TiO2 photocatalysis. In this Account, we describe our recent findings on the selective oxidation of organic substrates with O2 mediated by TiO2 photocatalysis. The transfer of O-atoms from O2 to the corresponding products dominates the selective oxidation of alcohols, amines, and alkanes mediated by TiO2 photocatalysis. We ascribe this to the concerted effect of both hvb(+) and ecb(-) of TiO2 in contribution to the oxidation products. These findings imply that O2 plays a unique role in its transfer into the products rather than independent role of ecb(-) scavenger. More importantly, ecb(-) plays a crucial role to ensure the high selectivity for the oxygenation of organic substrates. We can also use the half reactions such as those of the conduction band electron of TiO2 for efficient oxidation reactions with O2. To this end, efficient selective oxidation of organic substrates such as alcohols, amines, and aromatic alkanes with O2 mediated by TiO2 photocatalysis under visible light irradiation has been achieved. In summary, the concerted effect of hvb(+) and ecb(-) to implement one oxidation event could pave the way for selective oxofunctionalization of organic substrates with O2 by metal oxide photocatalysis. Furthermore, it could also deepen our understanding on the role of O2 and the elusive nature of oxygen species at the interface of TiO2, which, in turn, could shed new light on avant-garde photocatalytic selective redox processes in addressing the energy and environmental challenges of the future.

An unexpected fluctuating reactivity for odd and even carbon numbers in the TiO2-based photocatalytic decarboxylation of C2-C6 dicarboxylic acids

The degradation behaviours of five straight-chain dicarboxylic acids (from ethanedioic acid to hexanedioic acid) were compared in aqueous TiO2-based photocatalysis. When all other conditions were identical, the degradation rates were found to fluctuate regularly with the parity of the number of carbon atoms. Dicarboxylic acids with an even number of carbon atoms (e-DAs) always degraded more slowly than those acids with an odd number of carbon atoms (o-DAs). This unusual fluctuation in the reactivity for the degradation of dicarboxylic acids by TiO2-based photocatalysis is very closely related to the different pre-coordination modes of the acids with the photocatalyst. Attenuated total reflection FTIR (ATR-FTIR) of e-DAs labelled with (13)C showed that both carboxyl groups of the acid coordinate to TiO2 through bidentate chelating forms. In contrast, only one carboxyl group of the o-DAs coordinated to TiO2 in a bidentate chelating manner, whereas the other formed a monodentate binding linkage. The bidentate chelating form with bilateral symmetric coordination did not favour degradation. Isotope-labelling experiments were performed with (18)O2 to observe the different ways in which incorporated oxygen entered the initial decarboxylated products of e- and o-DAs. For the degradation of butanedioic acid, (45.9±0.5) % of the oxygen in the formed propanedioic acid came from H2O, whereas for pentanedioic acid, (97.4±0.2) % of the oxygen in the formed butanedioic acid came from H2O. Our results demonstrate that in TiO2-based photocatalysis, the reactivity of active species, such as ·OH/h(vb)(+), is far from non-selective and that the attacks of these active species on organic substrates are significantly affected by the coordination patterns of the substrates on the TiO2 surface.

Titania nanosheet-mediated construction of a two-dimensional titania/cadmium sulfide heterostructure for high hydrogen evolution activity

Two-dimensional titania nanosheets have been utilized to fabricate 2D titania-based mesoporous silica through a controlled sol-gel method, which can further serve as a robust and versatile template to construct various 2D heterostructures via a nanocasting technology. 2D titania-based CdS has been fabricated. This heterostructure manifests an excellent H2 -production rate of 285 μmol·h(-1) under visible-light irradiation and an apparent quantum yield of 6.9% at 420 nm.

Toward improving the graphene-semiconductor composite photoactivity via the addition of metal ions as generic interfacial mediator

We report a simple and general approach to improve the transfer efficiency of photogenerated charge carriers across the interface between graphene (GR) and semiconductor CdS by introducing a small amount of metal ions (Ca(2+), Cr(3+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+)) as "mediator" into their interfacial layer matrix, while the intimate interfacial contact between GR and CdS is maintained. This simple strategy can not only significantly improve the visible-light-driven photoactivity of GR-CdS semiconductor composites for targeting selective photoredox reaction, including aerobic oxidation of alcohol and anaerobic reduction of nitro compound, but also drive a balance between the positive effect of GR on retarding the recombination of electron-hole pairs photogenerated from semiconductor and the negative "shielding effect" of GR resulting from the high weight addition of GR. Our current work highlights that the significant issue on improving the photoactivity of GR-semiconductor composites via strengthening interfacial contact is not just a simple issue of tighter connection between GR and the semiconductor, but it is also the optimization of the atomic charge carrier transfer pathway across the interface between GR and the semiconductor.

Highly selective phenol production from benzene on a platinum-loaded tungsten oxide photocatalyst with water and molecular oxygen: selective oxidation of water by holes for generating hydroxyl radical as the predominant source of the hydroxyl group

Highly selective phenol production from benzene using Pt/WO₃ photocatalysts due to the unique reactivity of holes generating hydroxyl radicals.

Bi2WO6: A highly chemoselective visible light photocatalyst toward aerobic oxidation of benzylic alcohols in water

The visible-light-driven flower-like Bi₂WO₆ photocatalyst toward “green” chemistry oriented selective organic transformations in water is an essential pathway to sustainable development.

Ultrathin TiO2 layer coated-CdS spheres core-shell nanocomposite with enhanced visible-light photoactivity

Development of various strategies for controllable fabrication of core-shell nanocomposites (CSNs) with highly active photocatalytic performance has been attracting ever-increasing research attention. In particular, control of the ultrathin layer TiO2 shell in constructing CSNs in an aqueous phase is a significant but technologically challenging issue. Here, this paper demonstrates the interface assembly synthesis of CdS nanospheres@TiO2 core-shell photocatalyst via the electrostatic interaction of negatively charged water-stable titania precursor with positively charged CdS nanospheres (CdS NSPs), followed by the formation of the ultrathin-layer TiO2 shell through a facile refluxing process in aqueous phase. The as-formed CdS NSPs@TiO2 core-shell nanohybrid exhibits a high visible-light-driven photoactivity for selective transformation and reduction of heavy metal ions. The ultrathin TiO2 layer coated on CdS NSPs results in excellent light transmission property, enhanced adsorption capacity, and improved transfer of charge carriers and lifespan of photoinduced electron-hole pairs, which would prominently contribute to the significant photoactivity enhancement. It is anticipated that this facile aqueous-phase synthesis strategy could be extended to design a variety of more efficient CSN photocatalysts with controllable morphology toward target applications in diverse photoredox processes.

Visible-light-driven oxidation of primary C-H bonds over CdS with dual co-catalysts graphene and TiO2

Selective activation of primary C–H bonds for fine chemicals synthesis is of crucial importance for the sustainable exploitation of available feedstocks. Here, we report a viable strategy to synthesize ternary GR-CdS-TiO₂ composites with an intimate spatial integration and sheet-like structure, which is afforded by assembling two co-catalysts, graphene and TiO₂, into the semiconductor CdS matrix with specific morphology as a visible light harvester. The GR-CdS-TiO₂ composites are able to serve as a highly selective visible-light-driven photocatalyst for oxidation of saturated primary C–H bonds using benign oxygen as oxidant under ambient conditions. This work demonstrates a wide, promising scope of adopting co-catalyst strategy to design more efficient semiconductor-based photocatalyst toward selective activation of C–H bonds using solar light and molecular oxygen.

Nanostructure-based optoelectronic sensing of vapor phase explosives--a promising but challenging method

Optoelectronic sensing of gas phase hazardous chemicals is a newly explored field, which shows great advantages towards low concentration sensing when compared to normal gas sensing in the dark. Here, based on the recent progress on nanostructured vapor phase explosive gas sensors operated in dark conditions, the attractiveness of developing optoelectronic sensors for vapor phase explosive detection was highlighted. Furthermore, we try to propose some new insights to enhance optoelectronic sensing of vapor phase explosives. We suggest employing photocatalysis principles to enhance the sensitivity and employing a molecular imprinting technique (MIT) to enhance the selectivity.

Understanding the effect of surface/bulk defects on the photocatalytic activity of TiO2: anatase versus rutile

The sole effect of surface/bulk defects of TiO2 samples on their photocatalytic activity was investigated. Nano-sized anatase and rutile TiO2 were prepared by hydrothermal method and their surface/bulk defects were adjusted simply by calcination at different temperatures, i.e. 400-700 °C. High temperature calcinations induced the growth of crystalline sizes and a decrease in the surface areas, while the crystalline phase and the exposed facets were kept unchanged during calcination, as indicated by the characterization results from XRD, Raman, nitrogen adsorption-desorption, TEM and UV-Vis spectra. The existence of surface/bulk defects in calcined TiO2 samples was confirmed by photoluminescence and XPS spectra, and the surface/bulk defect ratio was quantitatively analyzed according to positron annihilation results. The photocatalytic activity of calcined TiO2 samples was evaluated in the photocatalytic reforming of methanol and the photocatalytic oxidation of α-phenethyl alcohol. Based on the characterization and catalytic results, a direct correlation between the surface specific photocatalytic activity and the surface/bulk defect density ratio could be drawn for both anatase TiO2 and rutile TiO2. The surface defects of TiO2, i.e. oxygen vacancy clusters, could promote the separation of electron-hole pairs under irradiation, and therefore, enhance the activity during photocatalytic reaction.

Defective TiO2 with oxygen vacancies: synthesis, properties and photocatalytic applications

Titanium dioxide (TiO2), as an important semiconductor metal oxide, has been widely investigated in the field of photocatalysis. The properties of TiO2, including its light absorption, charge transport and surface adsorption, are closely related to its defect disorder, which in turn plays a significant role in the photocatalytic performance of TiO2. Among all the defects identified in TiO2, oxygen vacancy is one of the most important and is supposed to be the prevalent defect in many metal oxides, which has been widely investigated both by theoretical calculations and experimental characterizations. Here, we give a short review on the existing strategies for the synthesis of defective TiO2 with oxygen vacancies, and the defect related properties of TiO2 including structural, electronic, optical, dissociative adsorption and reductive properties, which are intimately related to the photocatalytic performance of TiO2. In particular, photocatalytic applications with regard to defective TiO2 are outlined. In addition, we offer some perspectives on the challenge and new direction for future research in this field. We hope that this tutorial minireview would provide some useful contribution to the future design and fabrication of defective semiconductor-based nanomaterials for diverse photocatalytic applications.

Selective aerobic oxidation of amines to imines by TiO2 photocatalysis in water

Selective oxidation of benzylic amines to imines with atmospheric O2 is achieved in water on TiO2 under UV irradiation. The afforded imine could be easily separated and TiO2 can be recycled by filtration. To scale up, gram-scale imine products can be obtained.

Near-infrared light controlled photocatalytic activity of carbon quantum dots for highly selective oxidation reaction

Selective oxidation of alcohols is a fundamental and significant transformation for the large-scale production of fine chemicals, UV and visible light driven photocatalytic systems for alcohol oxidation have been developed, however, the long wavelength near infrared (NIR) and infrared (IR) light have not yet fully utilized by the present photocatalytic systems. Herein, we reported carbon quantum dots (CQDs) can function as an effective near infrared (NIR) light driven photocatalyst for the selective oxidation of benzyl alcohol to benzaldehyde. Based on the NIR light driven photo-induced electron transfer property and its photocatalytic activity for H2O2 decomposition, this metal-free catalyst could realize the transformation from benzyl alcohol to benzaldehyde with high selectivity (100%) and conversion (92%) under NIR light irradiation. HO˙ is the main active oxygen specie in benzyl alcohol selective oxidative reaction confirmed by terephthalic acid photoluminescence probing assay (TA-PL), selecting toluene as the substrate. Such metal-free photocatalytic system also selectively converts other alcohol substrates to their corresponding aldehydes with high conversion, demonstrating a potential application of accessing traditional alcohol oxidation chemistry.

Synthesis of fullerene-, carbon nanotube-, and graphene-TiO₂ nanocomposite photocatalysts for selective oxidation: a comparative study

A series of TiO(2)-graphene (GR), -carbon nanotube (CNT), and -fullerene (C(60)) nanocomposite photocatalysts with different weight addition ratios of carbon contents are synthesized via a combination of sol-gel and hydrothermal methods. Their structures and properties are determined by the X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), transmission electron microscopy (TEM), nitrogen adsorption-desorption, and photoelectrochemical measurements. Photocatalytic selective oxidation of benzyl alcohol to benzaldehyde is employed as a model reaction to evaluate the photocatalytic activity of the TiO(2)-carbon (GR, CNT, and C(60)) nanocomposites under visible light irradiation. The results reveal that incorporating TiO(2) with carbon materials can extend the adsorption edge of all the TiO(2)-carbon nanocomposites to the visible light region. For TiO(2)-GR, TiO(2)-CNT, and TiO(2)-C(60) nanocomposites, the photocatalytic activities of the composites with optimum ratios, TiO(2)-0.1% GR, TiO(2)-0.5% CNT, and TiO(2)-1.0% C(60), are very close to each other along with the irradiation time. Furthermore, the underlying reaction mechanism for the photocatalytic selective oxidation of benzyl alcohol to benzaldehyde over TiO(2)-carbon nanocomposites has been explored using different radical scavenger techniques, suggesting that TiO(2)-carbon photocatalysts follow the analogous oxidation mechanism toward selective oxidation of benzyl alcohol. The addition of different carbon materials has no significant influence on the crystal phase, particle size, and the morphology of TiO(2). Therefore, it can be concluded, at least for nanocomposites of TiO(2)-carbon (GR, CNT, and C(60)) obtained by the present approach, that there is no much difference in essence on affecting the photocatalytic performance of semiconductor TiO(2) among these three different carbon allotropes, GR, CNT, and C(60). Our findings point to the importance of a comparative study of semiconductor-carbon photocatalysts on drawing a relatively objective conclusion rather than separately emphasizing the unique role of GR and joining the graphene gold rush.

Synthesis of one-dimensional CdS@TiO₂ core-shell nanocomposites photocatalyst for selective redox: the dual role of TiO₂ shell

One-dimensional (1D) CdS@TiO₂ core-shell nanocomposites (CSNs) have been successfully synthesized via a two-step solvothermal method. The structure and properties of 1D CdS@TiO₂ core-shell nanocomposites (CdS@TiO₂ CSNs) have been characterized by a series of techniques, including X-ray diffraction (XRD), ultraviolet-visible-light (UV-vis) diffuse reflectance spectra (DRS), field-emission scanning electron microscopy (FESEM), photoluminescence spectra (PL), and electron spin resonance (ESR) spectroscopy. The results demonstrate that 1D core-shell structure is formed by coating TiO₂ onto the substrate of CdS nanowires (NWs). The visible-light-driven photocatalytic activities of the as-prepared 1D CdS@TiO₂ CSNs are evaluated by selective oxidation of alcohols to aldehydes under mild conditions. Compared to bare CdS NWs, an obvious enhancement of both conversion and yield is achieved over 1D CdS@TiO₂ CSNs, which is ascribed to the prolonged lifetime of photogenerated charge carriers over 1D CdS@TiO₂ CSNs under visible-light irradiation. Furthermore, it is disclosed that the photogenerated holes from CdS core can be stuck by the TiO₂ shell, as evidenced by controlled radical scavenger experiments and efficiently selective reduction of heavy-metal ions, Cr(VI), over 1D CdS@TiO₂ CSNs, which consequently leads to the fact that the reaction mechanism of photocatalytic oxidation of alcohols over 1D CdS@TiO₂ CSNs is apparently different from that over 1D CdS NWs under visible-light irradiation. It is hoped that our work could not only offer useful information on the fabrication of various specific 1D core-shell nanostructures, but also open a new doorway of such 1D core-shell semiconductors as visible-light photocatalysts in the promising field of selective transformations.