AgBr@TiO2/GO (graphene oxide) ternary composite photocatalyst was synthesized by fabricating core–shell-structured AgBr@TiO2 and anchoring it onto the surface of GO. The obtained samples were characterized by transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, ultraviolet–visible (UV–Vis) diffuse reflectance spectrum, and photoluminescence (PL) spectroscopy. It was found that the AgBr nanoparticles were prone to aggregation while the core–shell-structured AgBr@TiO2 possessed excellent dispersity. PL analysis revealed that the ternary-structured AgBr@TiO2/GO could effectively promote the separation rate of electron–hole pairs. Photocatalytic oxidation of benzyl alcohol to benzaldehyde under visible-light irradiation was selected as probe reaction to evaluate the photocatalytic activity of the different samples. It was found that the AgBr@TiO2/GO ternary composite exhibited evidently improved photocatalytic activity compared with AgBr, AgBr@TiO2, and AgBr/GO. On the basis of the experiment results, the photocatalytic oxidation mechanism of benzyl alcohol over AgBr@TiO2/GO is tentatively discussed.

A Z-scheme heterogeneous photocatalyst CdS–Au–BiVO4 was synthesized for the first time by photo-reduction and deposition–precipitation methods. The microstructures and optical properties of the as-prepared samples were investigated by means of scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS). Due to the oriented accumulation of electrons on the {010} facets of BiVO4 crystals, Au nanoparticles were successfully anchored on the {010} facets of BiVO4 crystals via the photo-reduction process. CdS was further selectively deposited on the surface of Au nanoparticles, benefitting from the strong S–Au interaction. Photocatalytic degradations of tetracycline and Rhodamine B indicated that CdS–Au–BiVO4 exhibits much higher photocatalytic activity than BiVO4, Au–BiVO4, and CdS–BiVO4. Radical trapping experiments confirmed that in the case of CdS–Au–BiVO4, the main reactive species responsible for organic contaminant degradation are h+, ˙OH, and ˙O2−, while only h+ can be produced in the case of CdS–BiVO4. Based on the photoelectrochemical analysis and radical trapping experiments, it can be deduced that the Z-scheme structure of CdS–Au–BiVO4 not only decreases the recombination rate of photo-generated carriers but also makes the holes and electrons keep a higher redox ability.

Small-molecule thiols such as cysteine (Cys) and glutathione (GSH) are essential for maintaining the cellular redox environment and play important roles in regulating various cellular functions. Therefore, it is significant to quantitatively detect the small-molecule thiols in clinical chemistry and biochemistry. Here, we synthesized a new probe RT by using a rhodol-based fluorescent dye with long emission wavelength (λem = 635 nm) as the fluorophore and the DNBS group as the response unit. It was found that the probe RT showed high response speed and selectivity toward Cys and GSH over other amino acids. After reacting with Cys/GSH, it shows a strong red fluorescence, corresponding to a color change from colorless to purple, which can be easily discriminated by the naked eye. The detection limit of the probe RT is as low as 24 nM to Cys and 20 nM to GSH. All these advantages of the probe RT make it possible for the quantitative detection of small-molecule thiols such as Cys and GSH in living organisms.

BiVO4 mesoporous single crystals (MSCs) were successfully prepared, for the first time, by a one-step hydrothermal method using the acidified BiVO4 precursor solution pre-impregnated silica as the template. It was revealed that the BiVO4 MSCs were formed by a double-diffusion mechanism. The O2 evolution rate over BiVO4 MSCs was improved nearly 10 times than that over BiVO4 bulk single crystals.

•A colorimetric and ratiometric fluorescence probe for detecting SO32− and HSO3− was synthesized.•The Probe showed high response speed, selectivity, and sensitivity towards SO32− and HSO3−.•The Probe showed high anti-interference ability in the co-existence of other species.•The detection is based on the nucleophilic addition of HSO3−/SO32− to the vinyl group.As one of the main atmospheric pollutants, sulfur dioxide (SO2) can be easily inhaled and turned into sulfite and bisulfite, which is harmful to both human health and ecological environment. Therefore, it is of significance to develop an effective method to detect the trace SO2 derivatives—SO32− and HSO3−. Herein, we synthesized a semi-cyanine-coumarin hybrid dye for detection of SO32− and HSO3−. Based on the nucleophilic addition of HSO3−/SO32− to the vinyl group, Probe 1 showed high response speed, selectivity, and sensitivity towards SO32− and HSO3−. Upon addition of HSO3−/SO32−, color obviously changes from blue to yellow which can be differentiated by naked eyes. Probe 1 displays colorimetric and ratiometric response toward HSO3− and SO32−. The detection limit is as low as 27.6 nM and the signal-to-background ratio in fluorescence intensity can reach 35-folds. Moreover, Probe 1 showed high selectivity and anti-interference ability in the co-existence of the environmental and biologic species.

Anatase TiO2 microcrystals containing ∼15% highly reactive {110} facets were successfully synthesized by a one-step hydrothermal method, in which H2O2, HF, and Cl− ions showed a synergistic effect on the formation of {110} facets. Benefiting from the surface heterojunction structure, TiO2 microcrystals with {110} facets showed an enhanced photocatalytic activity for dye degradation.

Core–shell structural CdS@SnO2 nanorods (NRs) were fabricated by synthesizing SnO2 nanoparticles with a solvent-assisted interfacial reaction and further anchoring them on the surface of CdS NRs under ultrasonic stirring. The morphology, composition, and microstructures of the obtained samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen adsorption–desorption. It was found that SnO2 nanoparticles can be tightly anchored on the surface of CdS NRs, and the thickness of SnO2 shells can be conveniently adjusted by simply changing the addition amount of SnO2 quantum dots. UV–vis diffuse reflectance spectrum indicated that SnO2 shell layer also can enhance the visible light absorption of CdS NRs to a certain extent. The results of transient photocurrents and photoluminescence spectra revealed that the core–shell structure can effectively promote the separation rate of electron–hole pairs and prolong the lifetime of electrons. Compared with the single CdS NRs, the core–shell structural CdS@SnO2 exhibited a remarkably enhanced photocatalytic activity for selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD) under visible light irradiation, attributed to the more efficient separation of electrons and holes, improved surface area, and enhanced visible light absorption of core–shell structure. The radical scavenging experiments proved that in acetonitrile solution, ·O2– and holes are the main reactive species responsible for BA to BAD transformation, and the lack of ·OH radicals is favorable to obtaining high reaction selectivity.Keywords: benzaldehyde; benzyl alcohol; CdS@SnO2; photocatalytic activity; selective oxidation;

•A ratiometric fluorescence probe for H2S was synthesized using dicyanoisophorone as fluorophore.•The probe showed long emission wavelength (643 nm) and large stokes shift (163 nm).•The probe exhibited high response speed and selectivity toward H2S.•The probe showed high sensitivity toward HS− and the detection limit is as low as 0.13 μM.Developing probes for selective and sensitive detection of hydrogen sulfide (H2S) has received much research attention, because H2S is an environmental toxin as well as an important signaling molecule to regulate physiological and pathological processes. In this work, a new colorimetric and ratiometric fluorescent probe (Probe 1) for H2S detection was synthesized by employing dicyanoisophorone based fluorescence dye as a fluorophore and azide group as the response unit. The synthesized Probe 1 showed a long emission wavelength (λem = 643 nm) and large stokes shift (λem − λabs = 163 nm). Based on the H2S-induced reduction of azide group to amino group, Probe 1 showed high response speed, sensitivity, and selectivity toward HS− under room temperature. Moreover, Probe 1 can ratiometrically respond to HS− and the detection limit is as low as 0.13 μM. It was proved that Probe 1 is suitable for quantitatively detecting HS− ions in river water samples. The numerous advantages of Probe 1 make it be potentially used for quantitative detection of H2S in environment and living organisms.

Developing probes for selective and sensitive detection of palladium in living organisms is of great importance. In this work, we synthesized a colorimetric and ratiometric fluorescent probe (Probe 1) with red light emission (λem = 643 nm) by employing an isophorone based fluorescent dye as the fluorophore and an allylcarbamate group as the response unit. Based on the Pd0-triggered cleavage reaction, Probe 1 showed high response speed, selectivity, and sensitivity towards palladium species. Upon addition of palladium, the absorption and emission spectra of Probe 1 exhibited obvious red-shifts, which can be easily discriminated by the naked eye. In terms of palladium, the detection limit is as low as 24.2 nM and the signal-to-noise ratio in fluorescence intensity can reach 85-fold. As a red emitting ratiometric sensor, Probe 1 can be potentially used for quantitative detection of palladium in living organisms.

A facile hydrothermal route employing H2O2 as structure-directing agent was explored to fabricate anatase microflowers with dominant {101} facets and anatase microspheres with exposed {001} facets. The influence of H2O2 concentration on crystal structure, morphology, and facet composition of TiO2 was investigated in detail. H2O2 plays a crucial role in determining the crystal structure, morphology, and exposed facets of TiO2. The presence of H2O2 favors the formation of anatase phase. When the concentration of H2O2 was in the range 0.7–3.3 M, anatase microflowers with dominant {101} facets were produced. In contrast, when the concentration of H2O2 was higher than 6.6 M, anatase microspheres with exposed {001} facets were formed. A mechanism was proposed to account for the influence of H2O2 on crystal structure and morphology of TiO2. Photocatalytic degradations of rhodamine B and 2,4-dichlorophenol indicated that anatase microspheres with exposed {001} facets showed much higher photocatalytic activity than anatase microflowers with dominant {101} facets.

Highlights•Ag/AgBr/RGO plasmonic photocatalyst was prepared by a facile multistep route.•Ag/AgBr/RGO exhibited strong light absorption in the visible region.•Ag/AgBr/RGO can effectively separate the photogenerated electrons and holes.•Ag/AgBr/RGO showed excellent visible light activity for the degradation of azo dyes.A novel visible light driven photocatalyst, reduced graphene oxide (RGO)-modified Ag/AgBr (Ag/AgBr/RGO), was synthesized by sequent double-jet precipitation, hydrothermal, and UV light reduction processes. The XPS and Raman results confirmed that part of GO was successfully reduced by hydrothermal treatment. Compared with Ag/AgBr, Ag/AgBr/RGO exhibited higher visible light photocatalytic activity for the degradation of methyl orange. The EIS analysis revealed that Ag/AgBr/RGO has better capability for charge transfer than Ag/AgBr. The excellent photocatalytic activity of Ag/AgBr/RGO is attributed to the strong visible light absorption of Ag nanoparticles and AgBr as well as the effective separation of photogenerated electrons and holes.Graphical abstract

Uniform cubic Ag@AgCl plasmonic photocatalyst was synthesized by a facile green route in the absence of organic solvent, in which a controllable double-jet precipitation technique was employed to fabricate homogeneous cubic AgCl grains and a photoreduction process was used to produce Ag nanoparticles (NPs) on the surface of AgCl. During the double-jet precipitation process, the presence of gelatin and Cl– ions at low concentration was necessary for the formation of cubic AgCl grains. Atomic force microscopy (AFM) was used to probe the morphological structure of Ag@AgCl grains for the first time, which showed that Ag NPs are anchored on the surface of AgCl grains like up-and-down mounds. Further characterization of the photocatalyst was also done by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–visible diffuse reflectance spectroscopy (DRS). The as-prepared Ag@AgCl plasmonic photocatalyst exhibited excellent photocatalytic efficiency for the degradation of the azo dye acid orange 7 (AO7), phenol, and 2,4-dichlorophenol (2,4-DCP). The photocatalytic mechanism was studied by radical-trapping experiments and the electron spin resonance (ESR) technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and the results indicated that •O2– and Cl0 are responsible for the rapid degradation of organic pollutants under visible-light irradiation.

•1D core–shell structural CdS@TiO2 was fabricated by a sol–gel method.•Thickness of TiO2 shell layer can be tuned by changing the additional amount of ammonia.•a-TiO2 shell layer promotes the separation of electron–hole pairs.•CdS@a-TiO2 showed improved activity for selectively oxidizing benzyl alcohol.One dimension (1D) core–shell structural CdS@TiO2 was fabricated by a modified sol–gel method. The thickness of amorphous TiO2 (a-TiO2) layer was adjusted by changing the amount of ammonia. Although a-TiO2 shell layer diminishes the visible light absorption in a certain extent, it largely increases the surface area of photocatalyst and effectively promotes the separation rate of photogenerated electron–hole pairs. It was revealed that a-TiO2 shell layer can effectively enhance the photocatalytic activity of CdS NRs for benzyl alcohol (BA) to benzaldehyde (BAD) transformation. Moreover, the core–shell structural CdS@a-TiO2 showed high stability and reusability for the selective oxidation of BA.Download high-res image (126KB)Download full-size image

A Z-scheme heterogeneous photocatalyst CdS–Au–BiVO4 was synthesized for the first time by photo-reduction and deposition–precipitation methods. The microstructures and optical properties of the as-prepared samples were investigated by means of scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS). Due to the oriented accumulation of electrons on the {010} facets of BiVO4 crystals, Au nanoparticles were successfully anchored on the {010} facets of BiVO4 crystals via the photo-reduction process. CdS was further selectively deposited on the surface of Au nanoparticles, benefitting from the strong S–Au interaction. Photocatalytic degradations of tetracycline and Rhodamine B indicated that CdS–Au–BiVO4 exhibits much higher photocatalytic activity than BiVO4, Au–BiVO4, and CdS–BiVO4. Radical trapping experiments confirmed that in the case of CdS–Au–BiVO4, the main reactive species responsible for organic contaminant degradation are h+, ˙OH, and ˙O2−, while only h+ can be produced in the case of CdS–BiVO4. Based on the photoelectrochemical analysis and radical trapping experiments, it can be deduced that the Z-scheme structure of CdS–Au–BiVO4 not only decreases the recombination rate of photo-generated carriers but also makes the holes and electrons keep a higher redox ability.

BiVO4 mesoporous single crystals (MSCs) were successfully prepared, for the first time, by a one-step hydrothermal method using the acidified BiVO4 precursor solution pre-impregnated silica as the template. It was revealed that the BiVO4 MSCs were formed by a double-diffusion mechanism. The O2 evolution rate over BiVO4 MSCs was improved nearly 10 times than that over BiVO4 bulk single crystals.