Photocatalyzed synthesis by using SnO2 as a photocatalyst is a green and alternative approach. Here, a nanocomposite of SnO2–Ag nanoparticles (AgNPs) and reduced graphene oxide (RGO) was prepared by a stepwise photocatalyzed approach. HRTEM shows that SnO2 and AgNPs were attached along the lattice matching each other and both of them were anchored upon RGO. Under UV irradiation, photo-excited holes from SnO2 were scavenged by ethanol while electrons were accumulated at the side of SnO2, leading to the reduction of both graphene oxide (GO) and Ag+. Here, SnO2 and metal Ag formed a heterostructure, and RGO played the dual role of conductor and support. During UV irradiation, the (101) facet of SnO2 offered a preferential growth direction for the (111) facet of AgNPs with an interfacial angle of 118°, which can be attributed to their similar D-spacings. A unique morphology of a combination of two semi-spheres was established. The energy-band structure of the composite was characterized to understand its mechanism of electrocatalysis. Owing to the difference between their binding energy in the heterostructure, electrons in AgNPs are transferred into SnO2, inducing AgNPs with positive charge and facilitating the redox of ractopamine (RAC). Under the optimal experimental conditions, a linear relationship between the relative amperometric response to RAC ranges from 5.0 × 10−8 to 5.5 × 10−6 M while the lower limit of detection reaches 2 × 10−8 M (S/N = 3.0).

•Water-soluble CdTe1−xSex QDs were synthesized by one-pot approach in aqueous phase.•Fluorescence emission spectra of CdTe1−xSex QDs were tuned by composition control.•The as-prepared CdTe1−xSex (0 ≤ x < 1) QDs have longer fluorescence lifetime of >80 ns.Water-soluble ternary-alloyed CdTe1−xSex quantum dots (QDs) have been synthesized via a simple one-pot approach in aqueous phase. The as-prepared CdTe1−xSex QDs show good crystallinity, excellent monodispersity, and a narrow size distribution with average size of 3.0 nm. Lattice parameters and band gaps of the ternary-alloyed CdTe1−xSex (0 ≤ x < 1) QDs are regulated respectively in linear and quadratic relationships with the Se content (x). By tuning composition, the photoluminescence (PL) emission wavelength of CdTe1−xSex can cover from 528.9 to 689.3 nm, and gradually moved to longer wavelengths with a decrease content of Se (x). The lifetime of CdTe1−xSex QDs is decreased gradually with the Se content (x) augment, attributing to the decreasing lattice spacing resulting from substitution of the larger Te atoms with the smaller Se atoms, bringing about a incremental plasmonic coupling effect at smaller inter-lattice fluorophore distance. However, the as-prepared CdTe1−xSex QDs (0 ≤ x < 1) have significantly longer fluorescence lifetimes of >80 ns with the maximum lifetime up to 174.64 ns. The longer life is good for the application of photoelectric conversion, fluorescent biomedical imaging and detecting.Download high-res image (310KB)Download full-size image

CeVO4 nanorods (NRs) were successfully synthesized via a one-step hydrothermal method using disodium edentate (EDTA) as a chelating agent. The CeVO4 NRs are assigned to the zircon-type tetragonal structure and exhibited pure single-crystals as determined by XRD analysis. FE-SEM images indicate that the as-prepared samples are present as square-section nanorods, and the length and sectional size of the CeVO4 NRs are found to be ∼1.5 μm and ∼100 nm, respectively. Moreover, the HRTEM images and SAED diffraction patterns confirm that the main exposed surfaces of the CeVO4 NRs were the (010) and (004) lattice planes with a high exposed percentage (ca. 96.77%) around the NRs and the growth direction was along the (200) lattice plane. The CeVO4 NRs presents a pure phase, with no other impurity phases identified from the FTIR and Raman spectra. XPS results indicate that the vanadium atoms on the surface exhibit a mixture of valence states, i.e., pentavalent state (V5+) and trivalent state (V3+), as dangling bonds around the oxygen vacancies were induced by EDTA desorption during hydrothermal process. An acetone gas sensor based on the CeVO4 NRs was fabricated, which exhibits a significant response (0.5 s) and recovery (80 s) with high selectivity at the optimum working temperature (108 °C). This is mainly due to the presence of the trivalent states (V3+), which serve as the active sites and provide a large number of oxygen vacancies (Vo) as identified by XPS and infrabar experiments at 300 ppm O2 (0.003 atm). Moreover, it has been demonstrated that the response to acetone for the gas sensor was crucially dependent on the adsorbed oxygen (Oads) on the (010) or (004) facets of the CeVO4 NRs, where the redox reaction with acetone occurred reversibly.

•CdSeTe@TiO2nanotubes were prepared with insitu growth process (*).•CdSeTe@ TNTs were used as high efficient visible-light photocatalysts.•CdSeTe@TNTs show a high photoinduced electron transfer rate of 7.98 × 109 s−1.•Ternary-alloyed CdTeSe QDs exhibit a long fluorescence lifetime of 105.82 ns.•The absorption edge of CdTeSe@TNTs is red shifted significantly toward 697 nm.High quality ternary-alloyed CdTeSe quantum dots (QDs) have been synthesized via a simple one-pot approach in aqueous phase. CdTeSe QDs show an average size of 3.0 nm with good crystallinity, excellent monodispersity and relatively narrow size distribution. TiO2 nanotubes (TNTs) were prepared by hydrothermal method with larger specific surface area (364.2 m2 g−1), and CdTeSe@TNTs were synthesized by in situ process. The absorption edge of CdTeSe@TNTs is red shifted significantly toward 697 nm. After sensitized with CdTeSe, the photoluminescence (PL) emission of CdTeSe@TNTs is significantly quenched, and the fluorescence lifetime of the composites is drastically decayed from 105.82 ns to 0.13 ns with a high photoinduced electron transfer rate (ket = 7.98 × 109 s−1) because of their high matchable lattice constant. In addition, under visible-light irradiation, the photocatalytic efficiency of rhodamine B (RhB) with CdTeSe@TNTs reaches 90% for 80 min. And the photocatalytic reaction rate constant for CdTeSe@TNTs is 0.0272 min−1, which is 5.4 and 3.4 times larger than that of pure TNTs and CdTeSe QDs, respectively. It is due to the broad visible absorption of CdTeSe@TNTs and the faster photoinduced electron transfer from CdTeSe QDs to TNTs.

•PDDA was used as a stabilizer and linker for functionalized TiO2 nanotubes.•Self-assembled process with palladium nanoparticles was synthesized.•After treated both H2SO4 and NaOH, the glucose response was magnified to 2.5 times.•The wide linear concentration range of glucose was obtained with a limit of 8 × 10− 8 M.Polydiallyldimethylammonium chloride, PDDA, was used as a stabilizer and linker for functionalized TiO2 nanotubes (TiO2 NTs). Self-assembled process with palladium nanoparticles (NPs) was successfully synthesized and used for the oxidation of glucose on glassy carbon electrodes. Based on the voltammetric and amperometric results, Pd NPs efficiently catalyzed the oxidation of glucose at − 0.05 V in the presence of 0.1 M NaCl and showed excellent resistance toward interference poisoning from such interfering species as ascorbic acid, uric acid and urea. To further increase sensitivity, the Pd NPs-PDDA-TiO2 NTs/GCE was electrochemically treated with H2SO4 and NaOH, the glucose oxidation current was magnified 2.5 times than that before pretreatments due to greatly enhancing the electron transport property of the sensor based on the increased defect sites and surface oxide species. In view of the physiological level of glucose, the wide linear concentration range of glucose (4 × 10− 7–8 × 10− 4 M) with a detection limit of 8 × 10− 8 M (S/N = 3) was obviously good enough for clinical application.

•2-D ZnTsPc/f-GN architecture was synthesized by electrostatic self-assembly method.•ZnTsPc/f-GN nanocomposites avoided the reaggregation of ZnTsPc and f-GN themselves.•An electrochemical BPA sensor was developed based on ZnTsPc/f-GN nanocomposites.•High absorption for BPA and electron deficiency on the surface of ZnTsPc/f-GN•The proposed sensor could be applied for detection of BPA in real samples.In this work, a novel zinc phthalocyanine tetrasulfonic acid (ZnTsPc)-functionalized graphene nanocomposites (f-GN) was synthesized by a simple and efficient electrostatic self-assembly method, where the positive charged GN decorated by (3-aminopropyl) triethoxysilane (APTES) was self-assemblied with ZnTsPc, a two dimensional (2-D) molecules. It not only enhanced its stability for the hybrid structure, but also avoided the reaggregation of ZnTsPc or f-GN themselves. Based on layered ZnTsPc/f-GN nanocomposites modified glassy carbon electrode, a rapid and sensitive sensor was developed for the determination of bisphenol A (BPA). Under the optimal conditions, the oxidation peak current increased linearly with the concentration of BPA in the range of 5.0 × 10− 8 to 4.0 × 10− 6 M with correlation coefficient 0.998 and limits of detection 2.0 × 10− 8 M. Due to high absorption nature for BPA and electron deficiency on ZnTsPc/f-GN, it presented the unique electron pathway arising from π–π stackable interaction during redox process for detecting BPA. The sensor exhibited remarkable long-term stability, good anti-interference and excellent electrocatalytic activity towards BPA detection.2-D ZnTsPc/f-GN architecture with high BPA absorption efficiency and excellent catalysis of central metal in ZnTsPc was highly promising for BPA sensor.

•Graphene sheets and ribbons show variant effect on photocatalysis in composite.•TiO2/graphene sheets or ribbons exhibit higher photocatalytic efficiency.•The composite of TiO2 and graphene sheets exhibits best photocatalytic activity.•Rectangular TiO2 sheets are dominated with a larger percentage of {0 0 1} facets.•Graphene oxide sheets/ribbons were photoreduced by TiO2 under UV irradiation.To investigate the effect of graphene sheets and ribbons on photocatalysis, the composite of anatase TiO2 nanosheets (TiO2-NS) and graphene materials was prepared. Graphene oxide sheet (GOS) was synthesized by a modified Hummers’ method, and graphene oxide ribbon (GOR) was formed by unzipping carbon nanotubes. UV–vis absorption spectrum and X-ray photoelectron spectroscopy (XPS) reveal that GOSs and GORs were photoreduced with TiO2-NS under ultraviolet irradiation. The as-prepared TiO2 nanosheets/graphene sheets (TS-GNSs) or ribbons (TS-GNRs) display drastically quenching of photoluminescence (PL) intensity and lower electron impedance, and TS-GNSs show better results than TS-GNRs. It is due to the excellent mobility of charge carriers and large surface area with graphene, which facilitate the separation of electron–hole pairs. Thus, TS-GNSs and TS-GNRs exhibit prominent photocatalytic activity under ultraviolet irradiation. The degradation efficiency of RhB is nearly 80% for TS-GNRs and 100% for TS-GNSs within 25 min. The lower degradation efficiency of TS-GNRs is due to the lower charge mobility of GNRs, which demonstrates that the excellent charge mobility of graphene plays a crucial role in composites for photodegradation.

•Hexagonal Ag nanoplates were synthesized by controlling of PVP and trisodium citrate.•Ag nanoplates/GN composite allowed adsorption and electron transfer of vanillin.•The composite with good dispersion exhibits enhanced surface area and good catalysis.•Vanillin on the Ag NPs/GN/GCE shows high sensitivity and selectivity.Hexagonal Ag nanoplates (NPs) were synthesized by polyvinylpyrrolidone (PVP) and trisodium citrate (TSC) which selectively absorbed to Ag (100) and Ag (111) surfaces, then were anchored to graphene (GN) to form novel Ag NPs/GN composite. The thickness of Ag NPs is ~ 4 nm and the length is 18–66 nm. Transmission electron microscopy (TEM) image shows that the plates are f-c-c crystals containing {111} facets on their two planar surfaces. Zeta potential indicated that the surface of Ag NPs/GN is negatively charged while vanillin is positively charged. Thus Ag NPs/GN modified on glass carbon electrodes (GCE) allowed abundant adsorption for vanillin and electron transfer between vanillin and Ag NPs/GN/GCE. Square wave voltammetry (SWV) results indicated that the over potential on Ag NPs/GN/GCE negatively shifts 52 mV than that on Ag NPs/GCE. Ag NPs/GN with enhanced surface area and good conductivity exhibited an excellent electrocatalytic activity toward the oxidation of vanillin. The corresponding linear range was estimated to be from 2 to 100 μM (R2 = 0.998), and the detection limit is 3.32 × 10− 7 M (S/N = 3). The as-prepared vanillin sensor exhibits good selectivity and potential application in practical vanillin determination.

•Flower Au@Pd nanoparticles -TiO2 nanotubes (NTs) hybrid nanostructures were prepared by a self-assembled technique.•(004) plane of TiO2NTs and (111) one of Au@Pd nanoparticles at the interface are compatible.•The electrochemical sensor exhibits high activity toward hydrazine (N2H4).In this paper, we reported a simple strategy for synthesizing well-defined TiO2NTs–Au@Pd hybrid nanostructures with prior TiO2 nanotube functionalization (F-TiO2NTs). TiO2NTs with larger surface area (BET surface area is 184.9 m2 g− 1) were synthesized by hydrothermal method, and the NTs are anatase phase with a range of 2–3 μm in length and 30–50 nm in diameter after calcined at 400 °C for 3 h. 3-Aminopropyl-trimethoxysilane (APTMS) as a coupling agent was reacted with the surface hydroxyl groups as anchoring sites for flower-shaped bimetallic Au@Pd nanostructures, self-assembling amine functionality on the surface of TiO2NTs. Note that two faces at the interface between F-TiO2NTs with (004) plane and Au@Pd nanostructures with (111) one of cubic Au and Pd nanoparticles are compatible, benefiting to the charge transfer between two components due to their crystalline coordination. The results showed that as-prepared F-TiO2NTs–Au@Pd hybrid nanostructures modified glassy carbon electrode (GCE) exhibits high electrocatalytic activity toward hydrazine (N2H4) at low potential and a linear response from 0.06 to 700 μM with the detection limit for N2H4 was found to be 1.2 × 10− 8 M (S/N = 3). Based on scan rate effect during the hydrazine oxidation, it indicates that the number of electrons transferred in the rate-limiting step is 1, and a transfer coefficient (α) is estimated as 0.73. The self-assembled F-TiO2NTs–Au@Pd hybrid nanostructures as enhanced materials present excellent electrocatalytic activity, fast response, highly sensitive and have a promising application potential in nonenzymatic sensing.

•A layer-by-layer assembly amperometric penicillin biosensor was proposed.•Graphene nanosheets, hematein, ionic liquids and penicillinase are modified on GCE.•Single graphene nanosheets with the presence of carboxylic acid groups were prepared.•A wide range from 1.25 × 10− 13 to 7.5 × 10− 3 M and low detection limit of 10− 13 M•The electrochemical mechanism is discussed and it was used in the detection of milk samples.In this study, we reported on a low detection limit penicillin biosensor with layer-by-layer (LbL) film containing single-graphene nanosheets (SGNs) preadsorbed with hematein, ionic liquids (ILs) and penicillinase. The penicillinase catalyzes the hydrolysis of penicillin to penicilloic acid, where H+ is liberated and monitored amperometrically with hematein as a pH indicator. The SGN-hematein/ILs/penicillinase biosensor exhibited excellent performance for penicillin in PBS with a wide range from 1.25 × 10− 13 to 7.5 × 10− 3 M, and a low detection limit of 10− 13 M (0.04 ppt, S/N ≥ 3). Furthermore, the detection of penicillin concentration in real sample (milk) had acceptable accuracy with the assay system.

The large bandgap of ZnO limits its application in photovoltaic devices, thus the semiconductor quantum dots (QDs), such as CdSe, is utilized to improve light-harvesting efficiency of solar cells. The CdSe@ZnO flower-rod core–shell nanocable arrays (CSZFRs) are prepared with a simple ion exchange method from aqueous solutions. The optical absorptions of the nanocable arrays can be controllably tuned to cover almost the entire visible spectrum (>750 nm) via quantum dots (QDs) sensitized attributed to the smaller band gap of CdSe. Moreover, a typical type II band alignment enhance the separation of photogenerated charge carriers, and reduce the electron–hole recombination within CSZFRs, demonstrated by the photoluminescence (PL) quenching after the formation of CSZFR hybrid structures. In addition, the CdSe-sensitized ZnO nanostructures demonstrate broad external quantum efficiency (EQE) in the spectrum from 300 to 740 nm. Therefore, the CSZFRs nanocable heterostruture exhibits a photovoltaic performance with a higher open-circuit photovoltage (−0.93 VAg/AgCl) and short-circuit photocurrent (1.00 mA cm−2).Graphical abstractHighlights► The CdSe@ZnO flower-rod core–shell nanocable arrays are used as photoanode. ► The photoanode of CdSe@ZnO nanocable exhibits higher photovoltaic performance. ► Ion exchange is a facile method to prepare the CdSe@ZnO nanocable. ► The CdSe-sensitized ZnO nanocables demonstrate a broad EQE in visible spectrum.

A novel nonenzymatic glucose sensor based on flower-shaped (FS) Au@Pd core–shell nanoparticles–ionic liquids (ILs i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide, [P(C6)3C14][Tf2N]) composite film modified glassy carbon electrodes (GCE) was reported. The Au@Pd nanocatalysts were prepared by seed-mediated growth method, forming the three-dimensional FS nanoparticles, where tens of small Pd nanoparticles (∼3 nm) aggregated on gold seeds (∼20 nm). The FS Au@Pd nanoparticle was a good candidate for the catalytic efficiency of nanometallic surfaces because of its flower-shaped nature, which has greater adsorption capacity. XPS analysis and zeta potential indicated that the surface of Pd atoms is positively charged, profiting the oxidation process of glucose. And ILs acted as bridge connecting Au@Pd one another and bucky gel as platform within the whole nanocomposite. So the modified electrode has higher sensitivity and selectivity owing to intrinsic synergistic effects of this nanocomposite. Amperometric measurements allow observation of the electrochemical oxidation of glucose at 0.0 V (vs. Ag/AgCl), the glucose oxidation current is linear to its concentration in the range of 5 nM–0.5 μM, and the detection limit was found to be 1.0 nM (S/N = 3). The as-prepared nonenzyme glucose sensor exhibited excellent stability, repeatability, and selectivity.

Stable Nafion–Au colloids were immobilized on a glassy carbon electrode (GCE) for detection of β-agonist clenbuterol by electroanalysis. The Au colloids were prepared by a one-step electrodeposition onto GCE, with obvious electrocatalytic activity present. The negatively charged Nafion film was an efficient barrier to negatively charged interfering compounds, resulting in accumulation of positively charged clenbuterol at the Nafion film. The electrochemical characters of the electrode during various modified steps in a redox probe system of K4[Fe(CN)6]/K3[Fe(CN)6] were confirmed by cyclic voltammetry (CV) and AC-impedance. In Britton–Robinson (B–R) buffer solution (pH = 2.0) and the potential range of −0.2 to 1.2 V, the Nafion–Au colloid modified electrode, compared to a bare GCE, exhibits obvious electrocatalytic activity towards the redox of clenbuterol by greatly enhancing the peak current with a linear calibration curve from 8.0 × 10−7 to 1.0 × 10−5 mol/L and a detection limit of (1.0 × 10−7 mol/L) (R = 0.996). The modified electrode shows high sensitivity, selectivity and reproducibility. The recovery for detecting clenbuterol (∼10−6 mol/L) in human serum is up to 98.19%.

Cobalt phthalocyanine (CoPc) was synthesized and self-assembled on the surface of nanoscale tin dioxide (SnO2) by in-situ process, marked as i, and Co–O interaction was verified to conjugate axially between macromolecule (CoPc) and SnO2 in CoPc/SnO2(i). The results indicated that the binding constant of CoPc/SnO2(i) was two-order higher than that of CoPc/SnO2(d) synthesized by dipping process, marked as d, while the numbers of binding sites were comparable in both samples. The degradation rate in the photocatalytic activity of CoPc/SnO2(i) was 32.5% higher than that of CoPc/SnO2(d) under visible-light irradiation for 150 min due to the effective electron separation and energy injection from LUMO of CoPc to conduction band of SnO2 for CoPc/SnO2(i) based on the strong interaction between CoPc and SnO2. The degradation recyclability of CoPc/SnO2(i) retained 48.8% in 10 times under the same circular photocatalytic process.

Nanoscale In2O3 powders doped with titanium were prepared by using InCl3·4H2O as a source matter. The materials doped with Ti4+ ions obviously showed the enhanced selectivity to ammonia sensor, compared with two reducing gases of H2 and CO, in the concentration range of 5–1000 ppm at a low operating current (165 mA, equal to 145 °C). Characterization of the materials was performed by thermal analysis, XRD, BET, FTIR, and magnetic susceptibility measurement. The mechanism of the selective gas sensing is proposed on the basis of the differences in gas molecular structure for adsorption and activation.