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Amino group functionalized hydrophobic ionic liquid, 1-ethylamine hydrobromide-3-methylimidazolium hexafluorophosphate (ILPF6) ionic liquid, was employed as the functional monomer to fabricate a carbon-based hole-conductor-free perovskite solar cells with high performances. The photoactive perovskite layer was facilely acquired by one-step spin-coating the precursor solution on a TiO2/FTO electrode surface, and subsequently annealed at an initial annealing at 60 °C for 3 min followed by annealing at 100 °C for 10 min to crystallize. The perovskite precursor solution was prepared by mixing ILPF6 ionic liquid and methylammonium iodide with an equal molar ratio of PbI2. In the optimized conditions, the power conversion efficiency (PCE) was enhanced from 10.08% to 13.01% by doping ILPF6 into the perovskite crystal film. This study demonstrates the multifaceted functions of ILPF6 ionic liquid in improving the efficiency and stability of PSCs. First, ILPF6 can react with PbI2 to form perovskite and can also play a role of the controlling and crosslinking reagent to obtain large grain size and minimize defects. Secondly, ILPF6 can improve the loading amount of perovskite crystals on the TiO2 film. Third, ILPF6 can promote the transport rate of the photogenerated carriers in the perovskite crystal layer. Lastly, ILPF6 ionic liquid with its high hydrophobicity creates a moisture barrier to improve the stability of PSCs effectively. The PSCs were stored under dark in a low relative humidity atmosphere (RH of 20%) at 25 °C without sealing. After 840 h, the PSC can maintain 94% of its initial PCE under the identical intensity illumination. This study demonstrates an excellent strategy to break through the bottleneck of the traditional PSCs and the enhanced effect of ionic liquid for carbon-based PSCs.

Synthesis and modification of salicylic acid (SA) adsorbed titanium dioxide (SA-TiO2) was proposed through a sol–gel reaction following annealing treatment. The prepared SA-TiO2 exhibited visible light absorption because of the formation of an intramolecular ligand to metal charge transfer transition. The photocatalytic activity of SA-TiO2 for the degradation of fast green FCF under visible light irradiation was evaluated. The experimental results suggest that the enhanced photocatalytic activity of SA-TiO2 is attributed to the visible light absorption ability. Moreover, •OH and •O2 − radicals are major active species involved in dye degradation. The practicality of SA-TiO2 was validated through the degradation of various dyestuff in environmental water samples under visible light irradiation.

A facile morphological specific precipitation method by volumetric control of the precursors has been demonstrated to achieve tetrapod-like and dodecahedron-like Ag3PO4 microparticles, which show superior visible-light responsive of photocatalytic activity when comparing to TiO2 (P25). This study also reveals that the tetrapod-like Ag3PO4 microparticles exhibit significantly higher photocatalytic activity (95.6% degradation within 20 min, k: 0.1937 min−1) than the dodecahedrons (78.9% degradation within 30 min, k: 0.0593 min−1) for the degradation of rhodamine B (RhB, 10 ppm) under low-power white light-emitting diode irradiation (300 mW cm−2), which may be attributed to the high reactivity of {110} facets. Moreover, holes and superoxide radicals were the main reactive species involved in RhB degradation.

Facile and template-free two-step synthesis of bismuth oxychloride/graphene oxide (BiOCl/GO) and bismuth oxychloride/reduced graphene oxide (BiOCl/rGO) photocatalysts for degradation of rhodamine B (RhB) under low-power white light–emitting diode (wLED) irradiation (1.6 W/cm2) and sunlight is demonstrated. These photocatalysts were characterized by transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, and micro-Raman, Fourier-transform infrared, X-ray photoelectron, and UV–Vis diffuse reflectance spectroscopy. Under wLED irradiation, the prepared BiOCl/rGO photocatalysts exhibited excellent photodegradation activity toward RhB through chromophore cleavage mechanism and toward phenol in the presence of RhB with notable dye-sensitized effect. Through scavenging experiments, superoxide radicals were notably involved in RhB degradation. With the highest charge separation efficiency and lowest recombination rate, the photocatalytic activity of BiOCl/rGO reached a maximum rate constant of 0.1899 min−1, 2.0 and 3.0 times higher than those of BiOCl/GO and BiOCl, respectively. In the stability study, only a slight loss (4.5%) in photodegradation was observed after BiOCl/rGO was used in five cycles of photodegradation runs. Compared with commonly used photocatalyst such as TiO2 (P25), BiOCl/rGO demonstrated superior photocatalytic activity and stability under wLED irradiation for various dyestuffs (rhodamine 6 G, methylene blue, and fast green FCF) in different environmental water samples (lake, pond, and sea water).

Facile synthesis of silver phosphate (Ag3PO4) microcrystals was developed for the novel application in the disinfection of pathogens with visible light. Ag3PO4 microcrystals from different synthesis routes were produced and characterised by scanning electron microscopy and UV–visible diffuse reflectance spectroscopy. The antibacterial activity of the Ag3PO4 microcrystals was also evaluated for its effectiveness in eradicating pathogens (Escherichia coli and Staphylococcus aureus) under white-light light-emitting-diode irradiation. The prepared Ag3PO4 microcrystals displayed higher and more stable photocatalytic antibacterial activity (>99% eradication rate within 10 min) comparing to Ag+ ions used only. This can be attributed to the oxidation of the photogenerated hole and the adsorption of Ag+ ions. This study demonstrated the strong photocatalytic activity of the as-prepared Ag3PO4 microcrystals, promising for industrial applications related to the eradication of pathogens from wastewater.

A serials of biomimetic photocatalyst zinc(II) meso-tetra(4-carboxyphenyl)porphyrinato (ZnTCP)-sensitized 3D hierarchical TiO2 hollow nanoboxes (TiO2-HNBs) assembled by six ordered nanosheets with dominant {001} facets exposure (ZnTCP@TiO2-HNBs) have been successfully synthesized by a facile one-pot solvothermal method via a topological transformation process with TiOF2 as template. Infrared spectra (IR), UV-vis spectroscopy, and X-ray photoelectron spectroscopy (XPS) confirmed that ZnTCP played a decisive role in constructing 3D hollow nanoboxes through the formation of ester bond combined to TiO2-HNBs, which also provided a transferring photo excited electrons bridge to sensitize TiO2-HNBs for enhancing visible-light response. Due to the superior sensitization and biomimetic activity of ZnTCP, the photodegradation rate of rhodamine B (RhB) of as-prepared ZnTCP@TiO2-HNBs with ZnTCP/TiOF2 mass ratio of 2% (T-2p) improves 3.6 times compared to that of TiO2-HNBs with a degradation yield of 99% for 2 h under simulated sunlight irradiation (> 420 nm). The enhanced photodegradation ability was attributed to synergistic visible photocatalytic mechanism of biomimetic catalyst, which can not only produce hydroxyl radical (•OH) and superoxide radical (•O2 −) coming from the excitation process of ZnTCP sensitized TiO2-HNBs, but also generate singlet oxygen (1O2) that was only provided by biomimetic enzyme porphyrins. Furthermore, the photocatalyst showed good recycling stability and dispersibility after five rounds, ascribed to ZnTCP strong chemical bonding to the support TiO2-HNBs. By means of electrochemical cyclic voltammetry analysis, the effect of central zinc ions and parent porphyrin rings on the redox property of biomimetic catalyst was studied.

A novel electropolymerizable material, 1-[3-(N-pyrrolyl) propyl]-3-butylimidazolium bromide (NPBimBr) ionic liquid, was synthesized and used as a modifier to functionalize graphene oxide nanosheets (GO) for fabricating an electrochemical sensor. X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy and electrochemical impedance spectroscopy were used to characterize both GO-NPBimBr and GO-poly(NPBimBr) film electrode. Electrochemical performance in the detection of bisphenol A at the GO-poly(NPBimBr) modified glassy carbon electrode (GCE) was investigated and optimized. Compared with the bare GCE, the oxidation peak current of bisphenol A at the nanocomposite film modified electrode was significantly increased. A good linear relationship between the oxidation peak current and the bisphenol A concentration was found in the range of 2.0 × 10−7 ∼ 1.0 × 10−5 mol L−1, with a detection limit of 1.7 × 10−8 mol L−1. The method was successfully applied to determine bisphenol A content in commercially available plastic drinking cups and the results are consistent with the ones from high performance liquid chromatography.

Effective surface-enhanced Raman scattering (SERS)-active substrates from gold nanoparticle and gold nanohole arrays were successfully fabricated through electron beam lithography with precise computer-aided control of the unit size and intergap distance. Their SERS performance was evaluated using 4-mercaptobenzoic acid (4-MBA). These gold arrays yielded strong SERS signals under 785 nm laser excitation. The enhancement factors for 4-MBA molecules on the prepared gold nanoparticle and nanohole arrays maxed at 1.08 × 107 and 8.61 × 106, respectively. The observed increase in SERS enhancement was attributed to the localized surface plasmon resonance (LSPR) wavelength shifting toward the near-infrared regime when the gold nanohole diameter increased, in agreement with the theoretical prediction in this study. The contribution of LSPR to the Raman enhancement from nanohole arrays deposited on fluorine-doped tin oxide glass was elucidated by comparing SERS and transmission spectra. This simple fabrication procedure, which entails employing electron beam lithography and the controllability of the intergap distance, suggests highly promising uses of nanohole arrays as functional components in sensing and photonic devices.

Various three-dimensional TiO2 hollow structures have attracted strong scientific and technological attention due to their excellent properties. 3D hierarchical TiO2 hollow nanocubes (TiO2-HNBs) are not good candidates for industrial photocatalytic applications due to their large energy gap which is only activated by UV light. Herein, visible-light-responsive carbon doped and coated TiO2-HNBs (C@TiO2-HNBs) with a dominant exposure of {001} facets have been prepared via a template-engaged topotactic transformation process using facile one-step solvothermal treatment and a solution containing ethanol, glucose and TiOF2. The effects of reaction time and glucose/TiOF2 mass ratio on the structure and performance of C@TiO2-HNBs were systematically studied. We found that glucose played an important role in providing H2O during the topological transformation from self-templated TiOF2 cubes into 3D hierarchical TiO2 hollow nanocubes versus dehydration reactions, where its main function was as a carbon source. Coated carbon was deposited predominantly on the surface as sp2 graphitic carbon in extended p conjugated graphite-like environments, and doped carbon mainly replaced Ti atoms in the surface lattice to form a carbonate structure. The results were confirmed using TEM SEM, EDS, XRD, FT-IR, XPS and Raman spectroscopic studies. The C@TiO2-HNBs achieved greatly improved RhB photodegradation activity under visible light irradiation. The catalyst prepared with glucose/TiOF2 at a mass ratio of 0.15 (T24-0.15) showed the highest photodegradation rate of 96% in 40 min, which is 7.0 times higher than those of the TiO2-HNBs and P25. This new synthetic approach proposes a novel way to construct carbon hybridized 3D hierarchical TiO2 hollow nanocubes by combining two modification methods, “element doped” and “surface sensitized”, at the same time.

In order to improve the photocatalytic activities of layered MOF bismuth terephthalate, five multiple halide anion doped bismuth terephthalate composites were prepared by doping three or four halide anions each with a molar ratio of X−/Bi3+ (X = F−, Cl−, Br−, I−) at 0.25. The F−, Cl−, Br− codoped and F−, Cl−, Br−, I− codoped bismuth terephthalate composites exhibit 41 and 35 times higher photocatalytic degradation activities for RhB, 7 and 6 times higher for salicylic acid than that of bismuth terephthalate. Excellent photocatalytic activities could be ascribed to the microstructure of multiple halide anion doped composites, large specific BET surface area and effective separation of photogenerated electron–hole pairs. Incorporating multiple negatively charged F−, Cl−, Br−, I− into layered bismuth terephthalate can improve the photocatalytic and electrochemical activities of bismuth terephthalate. The composites presented in this study can be potentially applied in photocatalysis and electrochemical fields as multifunctional materials.

In this study, a microwave-assisted synthesis of fluorescent egg-white-protected gold nanoclusters (ew–AuNCs) for sensing Hg2+ ions and melamine was developed, optimized, and evaluated. By conducting infrared spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we confirmed that clusters consisting of 22 Au atoms were successfully embedded in egg white. Transmission electron microscopy measurements revealed that the ew–AuNCs were well dispersed with an average diameter of 2.7 ± 0.7 nm. The ew–AuNCs exhibited red fluorescence emission (λem 648 nm) with high quantum yield (2.37%). In the presence of Hg2+ ions, the fluorescence of these ew–AuNCs was quenched because of the Hg2+–Au+ interaction. The relative change in fluorescence intensity at 648 nm was dependent on the concentration of Hg2+ ions. Detection of melamine was based on the diminished fluorescence quenching of ew–AuNCs by Hg2+ when melamine was added along with Hg2+. The limit of detection for Hg2+ ions and melamine was 0.89 nM and 0.46 μM, respectively. Determination of Hg2+ ions in a pond water sample and of melamine in milk and dog food samples was performed, and the recoveries from the developed method were >92.9%, confirming its potential for sensor applications.

Icosahedral gold nanocrystals (AuNCs) were synthesized by using the ionic liquid (IL) 1-(10-bromodecyl)-3-methyl-imidazolium bromide as a morphology-controlling reagent. The novel IL 1,3-di-(3-mercaptopropyl)-imidazolium bromide was employed as a bifunctional monomer to integrate the AuNCs onto the surface of a glassy carbon electrode (GCE) modified with gold nanoparticles. After interaction with thioglycolic acid (TGA) and activation of the carboxy groups, the antibody against squamous cell carcinoma antigen was immobilized on the modified GCE. Residual active sites were blocked with bovine serum albumin. The new materials and the steps for immunosensor fabrication were fully characterized. The reduction in peak current (using hexacyanoferrate as an electrochemical probe) due to the recognition of SCCA is linearly related to the SCCA concentration in the 0.02 to 10 ng mL−1 concentration range. The detection limit is as low as 12.6 pg mL−1 (at an S/N ratio of 3). The assay was applied to the quantitation of SCCA in human serum samples. The accuracy was validated by comparison with an ELISA method. The two methods displayed excellent consistency.

Dodecahedral gold nanocrystals (AuNCs) were synthesized by using a 1-(10-bromodecyl)-3-methylimidazolium bromide ionic liquid as functional monomer and protectant. AuNCs were self-assembled onto molybdenum disulfite (MoS2) nanosheets to fabricate AuNCs/MoS2 nanocomposite, which was drop-coated onto a glassy carbon electrode surface to generate an interface for transthyretin (TTR) immobilizing. With a similar chemical structure to thyroxine, tetrabromobisphenol A (TBBPA) was specifically recognized by transthyretin and the TTR/AuNCs/MoS2/GCE provides a sensing platform for TBBPA. Its sensing performance towards TBBPA was found significantly improved by the integration of AuNCs onto MoS2 nanosheets. Three conditions for assay development, such as incubation time, incubation temperature, and pH value, were investigated and found the optimum conditions were 200 s, 35 °C, and pH 7.0 respectively. Under these conditions, the ratio [Ri = (i0 − i)/i0] between the photocurrent variation (△i = i0 − i) and the original photocurrent (i0) is linearly related to the logarithm of TBBPA concentration (cTBBPA) from 0.1 nM to 1.0 μM. The linear relationship can be described by the following equation: Ri = 0.09092 log cTBBPA (M) + 0.8976 (R = 0.993). The detection limit is calculated to be 0.045 nM (S/N = 3). The photoelectrochemical immunosensor was used to accurately determine TBBPA concentration in South-Lake spiked water samples.

Monoclinic-phase bismuth vanadate (BiVO 4 ) with a 2.468 eV band gap exhibited enhanced synergic photodegradation activity toward methylene blue (MB) when combined with silver ions (Ag + ) in an aqueous solution under visible light irradiation. The mass ratio of AgNO 3 to BiVO 4 and the calcination temperature were discovered to considerably affect the degradation activity of BiVO 4 /Ag + . Superior photocatalytic performance was obtained when BiVO 4 was mixed with 0.01%(w/v) AgNO 3 solution, and complete degradation of MB was achieved after 25 min visible light irradiation, outperforming BiVO 4 or AgNO 3 solution alone. The enhanced photodegradation was investigated using systematic luminescence measurements, electrochemical impedance spectroscopy, and scavenger addition, after which a photocatalytic mechanism for MB degradation under visible light irradiation was identified that involved oxygen radicals and holes. This study also discovered the two dominating processes involved in enhancing the electron–hole separation efficiency and reducing their recombination rate, namely photoreduction of Ag + and the formation of a BiVO 4 /Ag heterojunction. The synergic effect between BiVO 4 and Ag + was discovered to be unique. BiVO 4 /Ag + was successfully used to degrade two other dyes and disinfect Escherichia Coli . A unique fluorescent technique using BiVO 4 and a R6G solution to detect Ag + ions in water was discovered.

AgX/MgBi2O6 composites (X = Cl, Br, and I), prepared from the hydrothermal procedure combined with a co-precipitation method, display unique visible light responsive photocatalytic activity. The catalytic performance of the AgX/MgBi2O6 composites were evaluated through the photodegradation of methylene blue (MB, 15 ppm) under white-light light-emitting diode irradiation (2.5 W, power density: 0.38 Wcm−2). Among the AgX/MgBi2O6 composites, the AgI/MgBi2O6 composite, with molar ratio of AgI to MgBi2O6 as 3:1, exhibited the highest photocatalytic performance within 20 min (degradation efficiency: 99.5 %) while MgBi2O6, AgCl/MgBi2O6, and AgBr/MgBi2O6 composites achieved degradation efficiency of 14.9 %, 24.9 % and 56.1 % respectively. The main reason of superior photocatalytic activity in AgI/MgBi2O6 composite attributes to the pn junction between AgI nanoparticles and MgBi2O6 effectively enhancing the charge separation efficiency and reducing the recombination rate of electron–hole pairs. This study revealed that hydroxyl and oxygen radicals are the major species involved in the degradation of MB from the photoactivated AgI/MgBi2O6 composite. To develop a practical application of this new material, the samples of AgI/MgBi2O6 composite have demonstrated excellent photocatalytic performance in degradation of various dyestuffs (92.3 %–99.5 % degradation within 10 min) under visible light irradiation and 99.8 % MB degradation under sunlight irradiation within 6 min.

Herein, a label-free colorimetric nanosensor for Hg(II) is developed utilizing the hindering effect of Hg(II) on the kinetic aspect of gold nanoparticle (AuNPs) growth on the surface of gold nanostars (AuNSs). H-AuNS probes are synthesized and modified by 2-[4-(2-hydroxyethel) piperazine-1-yl] ethanesulfonic acid (HEPES). After the formulation of the reagents and testing conditions are optimized, HEPES-capped AuNSs (H-AuNSs) demonstrates good selectivity and sensitivity towards Hg(II) determination. A H-AuNS probe, in the presence of HCl/Au(III)/H2O2, is capable of detecting a Hg(II) concentration range of 1.0 nM&ndash, 100 &micro, M, with a detection limit of 0.7 nM, at a signal-to-noise ratio of 3.0, and a visual detection limit of 10 nM with naked eyes. For practicality, the H-AuNS probe is evaluated by measuring Hg(II) in the environmental water matrices (lake water and seawater) by a standard addition and recovery study. The detection limits for environmental samples are found to be higher than the lab samples, but they are still within the maximum allowable Hg concentration in drinking water (10 nM) set by the US Environmental Protection Agency (EPA). To create a unique nanosensor, the competitive interaction between Hg(II) and Pt(IV) toward the H-AuNSs probe is developed into a logic gate, improving the specificity in the detection of Hg(II) ions in water samples.

This study demonstrated facile synthesis of silver phosphate (Ag3PO4) photocatalysts for the degradation of organic contaminants. Ag3PO4 microparticles from different concentrations of precursor, AgNO3, were produced and characterized by scanning electron microscopy, powder X-ray diffraction, and UV–visible diffuse reflectance spectroscopy. Degradation rates of methylene blue (MB) and phenol were measured in the presence of microparticles under low-power white-light light-emitting-diode (LED) irradiation and the reaction rate followed pseudo-first-order kinetics. The prepared Ag3PO4 microparticles displayed considerably high photocatalytic activity (>99.8% degradation within 10 min). This can be attributed to the microparticles’ large surface area, the low recombination rate of electron–hole pairs and the higher charge separation efficiency. The practicality of the Ag3PO4 microparticles was validated by the degradation of MB, methyl red, acid blue 1 and rhodamine B under sunlight in environmental water samples, demonstrating the benefit of the high photocatalytic activity from Ag3PO4 microparticles.

Ultrathin-layered carbon intercalated MoS2 hollow nanospheres (C/MoS2) were prepared with a hydrothermal method combined with high-temperature annealing using cetyltrimethylammonium bromide (CTAB) as the morphological control agent and ammonium molybdate as the molybdenum source. The ultrathin-layered C/MoS2, possessing a direct band-gap of ˜1.8 eV, can promote the visible light absorption and the charge-hole separation ideal for photoelectrochemical (PEC) sensing. Then, the gold nanoparticles (AuNPs) were integrated onto the C/MoS2 surface by in-situ reduction of chloroauric acid without adding any reductant to produce AuNPs/C/MoS2 nanocomposites. Subsequently, AuNPs/C/MoS2 nanocomposites and SCCA antibody (anti-SCCA) were sequentially modified on a glassy carbon electrode (GCE) surface to prepare a PEC immunosensing platform which was denoted as anti-SCCA(BSA)/AuNPs/C/MoS2/GCE. Under optimized conditions, the PEC immunosensor shows a broad linear range from 0.005 ng mL−1 to 8 ng mL−1 and a low detection limit of 1.8 pg mL−1 for determining SCCA. For the assay of SCCA in clinical serum samples, the results obtained from the PEC immunosensor are comparable to the generally accepted ELISA method from a commercial immunoassay kit.

Herein, cadmium sulfide–sensitized titanium dioxide (CdS/TiO2) deposited on a fluoride-doped tin oxide electrode is proposed for achieving the photoelectrocatalytic (PEC) degradation of methylene blue (MB). Under optimum conditions (six accumulative CdS depositions, 3.0-V DC applied biased potential, and 300-W Xe arc lamp irradiation), the prepared CdS/TiO2 films exhibited the highest PEC degradation of MB (82 ± 3%) compared with photocatalytic (70 ± 5%) or electrocatalytic (39 ± 5%) degradation. In addition, the higher current density (0.08425 mA/cm2) and the lower charge transfer resistance (78.5 Ω) of 6-CdS/TiO2 film were observed. These were attributable to the strong visible light absorption of CdS, the high charge separation efficiency in the CdS/TiO2 heterostructure , and the low electron–hole recombination rate from the applied biased potential. The feasibility of 6-CdS/TiO 2 film was evaluated by the MB degradation in environmental water samples, which demonstrated a high PEC activity (71 ± 3% degradation) of CdS/TiO2 film.