Utilizing Metal-Thiocatecholate Functionalized UiO-66 Framework for Photocatalytic Hydrogen Evolution Reaction.

Exploiting clean energy is essential for sustainable development and sunlight-driven photocatalytic water splitting represents one of the most promising approaches toward this goal. Metal-organic frameworks (MOFs) are competent photocatalysts owing to their tailorable functionality, well-defined structure, and high porosity. Yet, the introduction of the unambiguous metal-centered active site into MOFs is still challenging since framework motifs capable of anchoring metal ions firmly are lacking. Herein, the assembly using 1,4-dicarboxylbenzene-2,3-dithiol (H2 dcbdt) and Zr-Oxo clusters to give a thiol-functionalized UiO-66 type framework, UiO-66-dcbdt, is reported. The thiocatechols on the struts are allowed to capture transition metal (TM) ions to generate UiO-66-dcbdt-M (M  = Fe, Ni, Cu) with unambiguous metal-thiocatecholate moieties for photocatalytic hydrogen evolution reaction (HER). UiO-66-dcbdt-Cu is found the best catalyst exhibiting an HER rate of 4.18 mmol g-1  h-1  upon irradiation with photosensitizing Ru-polypyridyl complex. To skip the use of the external sensitizer, UiO-66-dcbdt-Cu is heterojunctioned with titanium dioxide (TiO2 ) and achieves an HER rate of 12.63 mmol g-1  h-1  (32.3 times that of primitive TiO2 ). This work represents the first example of MOF assembly employing H2 dcbdt as the mere linker followed by chelation with TM ions and undoubtedly fuels the rational design of MOF photocatalysts bearing well-defined active sites.

Plasmoelectric Potential in Plasmon-Mediated Electrochemistry.

Plasmon-mediated chemical reactions have attracted intensive research interest as a means of achieving desirable reaction yields and selectivity. The energetic charge carriers and elevated local temperature induced by the nonradiative decay of surface plasmons are thought to be responsible for improving reaction outcomes. This study reports that the plasmoelectric potential is another key contributor in plasmon-mediated electrochemistry. Additionally, we disclose a convenient and reliable method for quantifying the specific contributions of the plasmoelectric potential, hot electrons, and photothermal heating to the electroreduction of oxygen at the plasmonic Ag electrode, revealing that the plasmoelectric potential is the dominating nonthermal factor under short-wavelength illumination and moderate electrode bias. This work elucidates novel mechanistic understandings of plasmon-mediated electrochemistry, facilitating high-performance plasmonic electrocatalyst design optimization.

Thermal and Nonthermal Effects in Plasmon-Mediated Electrochemistry at Nanostructured Ag Electrodes.

Hot carriers (HCs) and thermal effects, stemming from plasmon decays, are crucial for most plasmonic applications. However, quantifying these two effects remains extremely challenging due to the experimental difficulty in accurately measuring the temperature at reaction sites. Herein, we provide a novel strategy to disentangle HCs from photothermal effects based on the different traits of heat dissipation (long range) and HCs transport (short range), and quantitatively uncover the dominant and potential-dependent role of photothermal effect by investigating the rapid- and slow-response currents in plasmon-mediated electrochemistry at nanostructured Ag electrode. Furthermore, the plasmoelectric surface potential is found to contribute to the rapid-response currents, which is absent in the previous studies.

Dispersive Plasmon Damping in Single Gold Nanorods by Platinum Adsorbates.

Surface modifications of plasmonic nanoparticles with metal adsorbates are essential in applications such as plasmonic sensing, plasmon-enhanced photocatalysis, etc., where spectral broadening is usually observed. A single particle study is presented on plasmon damping by adsorption of platinum (Pt) clusters. Single particle dark-field spectroscopy is employed to measure exactly the same gold nanorod before and after the Pt adsorption. The Pt-induced plasmon damping in terms of linewidth increase is found dependent on the resonance wavelength of the measured nanorod, which is dispersive in nature. The measured dispersion generally matches the theoretical prediction, and it basically exhibits a gradual increase with decreasing resonance energy. This increase can be attributed to the fact that the nanorod as a better resonator is more susceptible to the Pt adsorption than the spherical particles. Moreover, simulated results based on discrete dipole approximation method further indicate that the damping is mainly contributed from the adsorbates on the ends of the nanorod and independent on the type of the metal adsorbed. Knowledge and insights gained in this study can be very important for the design and fabrication of plasmonic heterostructures as functional nanomaterials.

Stereoisomeric profiling of pharmaceuticals ibuprofen and iopromide in wastewater and river water, China.

Stereoisomeric compositions can provide insights into sources, fate, and ecological risks of contaminants in the environment. In this study, stereoisomeric profiles of ibuprofen and iopromide were investigated in wastewater and receiving surface water of the Pearl River Delta, south China. The enantiomeric fraction (EF) of ibuprofen was 0.108-0.188 and 0.480, whereas the isomer ratio (IR) of iopromide was 1.426-1.673 and 1.737-1.898 in the influent and final effluent, respectively, suggesting stereoselective degradation occurred for both pharmaceuticals during wastewater treatment. Ibuprofen showed enantioselective degradation in the anaerobic, anoxic, and aerobic conditions, whereas iopromide displayed isomer-selective degradation only under the aerobic condition. In the river waters, the EF of ibuprofen was 0.130-0.327 and the IR of iopromide was 1.500-2.531. The results suggested that pharmaceuticals in the mainstream Pearl River were mainly from discharge of treated wastewater, whereas in the tributary rivers and urban canals, direct discharge of untreated wastewater represented a significant contribution. The IR of iopromide can be an applicable and efficient tracer for wastewater discharge in the environment.

Near-infrared-activated anticancer platinum(IV) complexes directly photooxidize biomolecules in an oxygen-independent manner.

Conventional light-driven cancer therapeutics require oxygen and visible light to indirectly damage biomolecules, limiting their efficacy in deep, hypoxic tumours. Here we report the use of near-infrared-activated small-molecule Pt(IV) photooxidants to directly oxidize intracellular biomolecules in an oxygen-independent manner, achieving controllable and effective elimination of cancer stem cells. These Pt(IV) complexes accumulate in the endoplasmic reticulum and show low toxicity in the dark. Upon irradiation, the resultant metal-enhanced photooxidation effect causes them to robustly photooxidize survival-related biomolecules, induce intense oxidative stress, disrupt intracellular pH (pHi) homeostasis and initiate nonclassical necrosis. In vivo experiments confirm that the lead photooxidant can effectively inhibit tumour growth, suppress metastasis and activate the immune system. Our study validates the concept of metal-enhanced photooxidation and the subsequent chemotherapeutic applications, supporting the development of such localized photooxidants to directly damage intracellular biomolecules and decrease pHi as a strategy for effective metal-based drugs.

Facile Surfactant-, Reductant-, and Ag Salt-free Growth of Ag Nanoparticles with Controllable Size from 35 to 660 nm on Bulk Ag Materials.

Morphologically and dimensionally controlled growth of Ag nanocrystals has long been plagued by surfactants or capping agents that complicate downstream applications, unstable Ag salts that impaired the reproducibility, and multistep seed injection that is troublesome and time-consuming. Here, we report a one-pot electro-chemical method to fast (∼2 min) produce Ag nanoparticles from commercial bulk Ag materials in a nitric acid solution, eliminating any need for surfactants or capping agents. Their size can be easily manipulated in an unprecedentedly wide range from 35 to 660 nm. Furthermore, the Ag nanoparticles are directly grown on the Ag substrate, highly desirable for promising applications such as catalysis and plasmonics. The mechanistic studies reveal that the concentration of Ag+ in the diffusion layer nearby the surface, controlled by the magnitude and duration of voltage, is critical in governing the nanoparticle formation (<1.3 mM) and its dimensional adjustability.

Plasmonic metal nanostructures: concepts, challenges and opportunities in photo-mediated chemical transformations.

Plasmonic metal nanostructures (PMNs) are characterized by the plasmon oscillation of conduction band electron in response to external radiation, enabling strong light absorption and scattering capacities and near-field amplification. Owing to these enhanced light-matter interactions, PMNs have garnered extensive research interest in the past decades. Notably, a growingly large number of reports show that the energetics and kinetics of chemical transformations on PMNs can be modified upon photoexcitation of their plasmons, giving rise to a new paradigm of manipulating the reaction rate and selectivity of chemical reactions. On the other hand, there is urgent need to achieve clear understanding of the mechanism underlying the photo-mediated chemical transformations on PMNs for unleashing their full potential in converting solar energy to chemicals. In this perspective, we review current fundamental concepts of photo-mediated chemical transformations executed at PMNs. Three pivotal mechanistic questions, i.e., thermal and nonthermal effects, direct and indirect charge transfer processes, and the specific impacts of plasmon-induced potentials, are explored based on recent studies. We highlight the critical aspects in which major advancements should be made to facilitate the rational design and optimization of photo-mediated chemical transformations on PMNs in the future.

Active Manipulation of NIR Plasmonics: the Case of Cu2-xSe through Electrochemistry.

Active control of nanocrystal optical and electrical properties is crucial for many of their applications. By electrochemical (de)lithiation of Cu2-xSe, a highly doped semiconductor, dynamic and reversible manipulation of its NIR plasmonics has been achieved. Spectroelectrochemistry results show that NIR plasmon red-shifted and reduced in intensity during lithiation, which can be reversed with perfect on-off switching over 100 cycles. Electrochemical impedance spectroscopy reveals that a Faradaic redox process during Cu2-xSe (de)lithiation is responsible for the optical modulation, rather than simple capacitive charging. XPS analysis identifies a reversible change in the redox state of selenide anion but not copper cation, consistent with DFT calculations. Our findings open up new possibilities for dynamical manipulation of vacancy-induced surface plasmon resonances and have important implications for their use in NIR optical switching and functional circuits.

Persistence, temporal and spatial profiles of ultraviolet absorbents and phenolic personal care products in riverine and estuarine sediment of the Pearl River catchment, China.

A variety of personal care products have been classified as emerging contaminants (ECs). Occurrence, fate, spatial and vertical profiles of 13 ultraviolet absorbents, triclocarban (TCC) and its dechlorinated products, triclosan (TCS), 2-phenylphenol and parabens were investigated in riverine and estuarine sediment of the Pearl River catchment, China. Bisphenol A (BPA), a widely applied plasticizer, was also investigated. The ECs were widely present in the bed sediment. TCC was the most abundant with a maximum concentration of 332ngg-1 dry weight. The other prominent ECs included BPA, TCS, octocrylene, and benzotriazole UV stabilizers UV326 and UV328. Treated wastewater effluent was the major source of the ECs in the riverine sediment. TCC, BPA, TCS, methyparaben, UV531, UV326, and UV328 were also detected throughout the estuarine sediment cores, indicating their persistence in the sediment. Temporal trends of the ECs in the sediment cores reflected a combined effect of industrial development, population growth, human life quality improvement, and waste treatment capacity in the Pearl River Delta over the last decades. TCC dechlorination products were frequently detected in the bed sediment with higher levels near treated effluent outlets but only occasionally observed in the sediment cores, suggesting insignificant in-situ TCC dechlorination in the sediment.

Rapid Seedless Synthesis of Gold Nanoplates with Microscaled Edge Length in a High Yield and Their Application in SERS.

We report a facile and reproducible approach toward rapid seedless synthesis of single crystalline gold nanoplates with edge length on the order of microns. The reaction is carried out by reducing gold ions with ascorbic acid in the presence of cetyltrimethylammonium bromide (CTAB). Reaction temperature and molar ratio of CTAB/Au are critical for the formation of gold nanoplates in a high yield, which are, respectively, optimized to be 85 °C and 6. The highest yield that can be achieved is 60 % at the optimized condition. The synthesis to achieve the microscaled gold nanoplates can be finished in less than 1 h under proper reaction conditions. Therefore, the reported synthesis approach is a time- and cost-effective one. The gold nanoplates were further employed as the surface-enhanced Raman scattering substrates and investigated individually. Interestingly, only those adsorbed with gold nanoparticles exhibit pronounced Raman signals of probe molecules, where a maximum enhancement factor of 1.7 × 107 was obtained. The obtained Raman enhancement can be ascribed to the plasmon coupling between the gold nanoplate and the nanoparticle adsorbed onto it.

Quasi-targeted analysis of hydroxylation-related metabolites of polycyclic aromatic hydrocarbons in human urine by liquid chromatography-mass spectrometry.

Metabolite identification is crucial for revealing metabolic pathways and comprehensive potential toxicities of polycyclic aromatic hydrocarbons (PAHs) in human body. In this work, a quasi-targeted analysis strategy was proposed for metabolite identification of monohydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) in human urine using liquid chromatography triple quadruple mass spectrometry (LC-QqQ-MS/MS) combined with liquid chromatography high resolution mass spectrometry (LC-HRMS). Potential metabolites of OH-PAHs were preliminarily screened out by LC-QqQ-MS/MS in association with filtering in a self-constructed information list of possible metabolites, followed by further identification and confirmation with LC-HRMS. The developed method can provide more reliable and systematic results compared with traditional untargeted analysis using LC-HRMS. In addition, data processing for LC-HRMS analysis were greatly simplified. This quasi-targeted analysis method was successfully applied to identifying phase I and phase II metabolites of OH-PAHs in human urine. Five metabolites of hydroxynaphthalene, seven of hydroxyfluorene, four of hydroxyphenanthrene, and three of hydroxypyrene were tentatively identified. Metabolic pathways of PAHs in human body were putatively revealed based on the identified metabolites. The experimental results will be valuable for investigating the metabolic processes of PAHs in human body, and the quasi-targeted analysis strategy can be expanded to the metabolite identification and profiling of other compounds in vivo.

Multi-target determination of organic ultraviolet absorbents in organism tissues by ultrasonic assisted extraction and ultra-high performance liquid chromatography-tandem mass spectrometry.

A sensitive and reliable method was developed for multi-target determination of 13 most widely used organic ultraviolet (UV) absorbents (including UV filters and UV stabilizers) in aquatic organism tissues. The organic UV absorbents were extracted using ultrasonic-assisted extraction, purified via gel permeation chromatography coupled with silica gel column chromatography, and determined by ultra-high performance liquid chromatography-tandem mass spectrometry. Recoveries of the UV absorbents from organism tissues mostly ranged from 70% to 120% from fish filet with satisfactory reproducibility. Method quantification limits were 0.003-1.0ngg(-1) dry weight (dw) except for 2-ethylhexyl 4-methoxycinnamate. This method has been applied to analysis of the UV absorbents in wild and farmed aquatic organisms collected from the Pearl River Estuary, South China. 2-Hydroxy-4-methoxybenzophenone and UV-P were frequently detected in both wild and farmed marine organisms at low ngg(-1)dw. 3-(4-Methylbenzylidene)camphor and most of the benzotriazole UV stabilizers were also frequently detected in maricultured fish. Octocrylene and 2-ethylhexyl 4-methoxycinnamate were not detected in any sample. This work lays basis for in-depth study about bioaccumulation and biomagnification of the UV absorbents in marine environment.

Profile and behavior of antiviral drugs in aquatic environments of the Pearl River Delta, China.

Occurrence and behavior of six antiviral pharmaceuticals (acyclovir, ganciclovir, oseltamivir, ribavirin, stavudine and zidovudine) and one active metabolite oseltamivir carboxylate were investigated in wastewater, landfill leachate, river water, reservoir and well water in the vicinity of municipal landfills in the Pearl River Delta, China. Acyclovir was the only antiviral detected in the wastewater at 177-406 (mean=238) and 114-205 (mean=154) ng L(-1) in the influent and final effluent, respectively. Aerobic biodegradation appeared to be the main process for the elimination of acyclovir in the wastewater. Acyclovir was also the only antiviral quantitatively detected in the Pearl River and its tributaries, with a maximum concentration up to 113 ng L(-1). Treated wastewater was a major source of acyclovir in the rivers. The highest concentration of acyclovir was observed in winter in the river water and the dilution effect by precipitation was suggested to be the dominant factor impacting the seasonal pattern of acyclovir in the rivers. No antivirals were quantitatively detected in the well water whereas acyclovir was frequently detected in the reservoirs at a maximal concentration of 33.6 ng L(-1) in the vicinity of the municipal landfills. However, source identification and fate of acyclovir in the reservoirs pend on further research.

Occurrence and ecological potential of pharmaceuticals and personal care products in groundwater and reservoirs in the vicinity of municipal landfills in China.

Pharmaceutical and personal care products (PPCPs), including antibiotics, azole anti-fungals, non-steroid anti-inflammatory drugs, lipid regulators, parabens, antiseptics, and bisphenol A, were investigated in groundwater and reservoirs in the vicinity of two municipal landfills in the metropolis of Guangzhou, South China. Dehydroerythromycin, sulfamethoxazole, fluconazole, salicylic acid, methylparaben, triclosan, and bisphenol A were the mostly frequently detected PPCPs in the groundwater at low ng L(-1) levels. In the reservoirs, the PPCPs were widely detected at higher frequencies and concentrations, especially sulfamethoxazole, propiconazole, and ibuprofen, with maximal concentrations above 1 µg L(-1). The PPCPs in the groundwater did not show significant seasonal differences or spatial trends. However, in the reservoirs, higher PPCP concentrations were observed in spring than in other seasons. The anti-bacterials in the groundwater posed medium risks to algae. In the reservoirs, the sulfonamides and macrolides posed low to high risks, while ibuprofen, salicylic acid, and clofibric acid presented low to medium risks to aquatic organisms. Overall, the results showed that the PPCP contaminants and subsequent ecological risks in the groundwater and surface water in the vicinity of the landfills may be of serious concern. More research is needed to better correlate the landfill leachates and PPCP contamination in the nearby aquatic environments.