The black TiO2–coated Cu nanoparticles with oxygen resistance were fabricated in this work. The activity of Cu@TiO2 for CO2 photoreduction under visible-light irradiation is markedly higher than that ...of bared black TiO2
Display omitted
•Fabrication of black TiO2–coated Cu nanoparticles with oxygen resistance of metallic Cu.•The metallic Cu nanoparticles promote the formation of oxygen vacancies in TiO2 through the metal-oxide interaction.•The metallic Cu nanoparticles facilitate the separation of photogenerated electron-hole pairs of TiO2.•black TiO2–coated Cu photocatalysts exhibit higher activity for the reduction of CO2 than that of TiO2.
Nanosized metallic copper could be a replacement of noble metals for improving photoactivity of TiO2-based photocatalysts, but it tends to be oxidized by oxygen in surroundings. To avoid this, black TiO2−coated Cu nanoparticles (denoted as Cu@TiO2) were constructed in the present work, and their photoactivity for the photoreaction of CO2 with H2O vapor under visible-light irradiation was explored. X-ray diffraction, transmission electron microscopy and selected area electron diffraction analysis for the used Cu@TiO2 confirm the hierarchical structure of Cu@TiO2 and oxygen resistance of metallic Cu. The photocatalytic activity for Cu@TiO2 (∼4%Cu) reaches 1.7 times of that for its counterpart, bared black TiO2. The improved photoactivity is attributed to the embedded metallic Cu, which promotes the formation of oxygen vacancies in TiO2 through the metal-oxide interaction, thus increasing the visible-light absorption of Cu@TiO2 and the adsorption of CO2 on their surface. Furthermore, the metallic Cu increases photoinduced charge-separation of TiO2 through trapping electrons as evidenced by transient photocurrent measurements. The present work sheds light on developing new type of metal-oxide based visible-light-driven photocatalysts.
Surface-Ti-rich SrTiO3 exhibits the highest activity for photocatalytic CO2 reduction, which can be ascribed to the enhanced harvesting to simulated solar light, high proportion of active species ...derived from CO2 adsorption on the surface, and Ti-ion exposure.
Display omitted
•SrTiO3, surface-Ti-rich SrTiO3 and Sr(OH)2-decorated SrTiO3 were prepared.•Surface-Ti-rich SrTiO3 exhibits the highest activity for photocatalytic CO2 reduction.•It is speculated that the only CO2 adsorbed on Ti ions has a higher reactivity under light irradiation.
Perovskite oxide SrTiO3 is a promising semiconductor photocatalyst for CO2 reduction, which has two possible chemical surfaces—TiO2-terminated and SrO-terminated surfaces. Up to now, the effect of chemical surface and its modification on CO2 adsorption, activation and sequential photocatalytic reduction is not established. In the work, SrTiO3, surface-Ti-rich SrTiO3 and Sr(OH)2-decorated SrTiO3 were prepared and their structural, surface, and optical properties and photocatalytic activity were explored. It is found that the absorption edge of surface-Ti-rich SrTiO3 shifted toward visible-light region as compared with that of the other two photocatalysts, which is attributed to the decreased Ti 3d ground-state level at the surface. Bicarbonate- (HCO3−) and bidentate carbonate-like (b-CO3=) species are the main species for CO2 adsorption on the surface-Ti-rich SrTiO3, whereas, besides HCO3− and b-CO3=, plenty of monodentate carbonate-like species (m-CO3=) that has relatively low reactivity is present on the SrTiO3 and Sr(OH)2-decorated photocatalysts. As a result, the surface-Ti-rich SrTiO3 exhibits the highest activity for CO2 reduction. Furthermore, although Sr(OH)2-decoration and SrO-terminated surfaces facilitate CO2 fixing, the produced surface species are attached to the weakly active Sr ions, giving rise to the lower reactivity. The present work might supply a guide for designing highly active perovskite–type semiconductors for photocatalysis.
A novel amino-functionalized magnetic adsorbent (Fe3O4@C@DETA) was developed for adsorption of Cr(III) and Cr(III)-EDTA from wastewater. Fe3O4@C@DETA were successfully prepared by modification of ...Fe3O4@C with diethylenediamine (DETA), which exhibits a core-shell structure and sufficient saturation magnetization. Fe3O4@C@DETA exhibits much better adsorption performance for Cr(III) and its chelates than the Fe3O4@C because of newly introduced amino active sites. The enhanced adsorption capacity of Fe3O4@C@DETA for Cr(III) is 44.74 mg g−1 (at 25 °C and pH 3.0), which is due to the surface coordination with the newly introduced amino functional sites. The Cr(III)-EDTA anions as a whole was adsorbed through the electrostatic interaction with protonated amino species of the Fe3O4@C@DETA and have maximum adsorption capacity of 47.27 mg g−1 (at 25 °C and pH 3.0). The adsorption data of free and EDTA coordinated Cr(III) were followed the Langmuir equation, while the adsorption dynamics was well explained by pseudo second order model indicating the chemical nature of adsorption process. The higher concentration of Ca2+ ions in the wastewater compete for adsorption sites and inhibit the Cr(III) removal, while on other hand Ca2+ ions promotes the adsorption of Cr(III)-EDTA, because of electrostatic interaction with adsorbent active sits. Furthermore, the adsorbent can be easily separated by external magnetic field and regenerated in acidic solution. The adsorbent is stable, recyclable and have more than 75% regeneration efficiency and can be repeatedly used in the adsorption process.
Display omitted
•DETA functionalized magnetic carbon-based adsorbent was developed.•Fe3O4@C@DETA exhibits higher adsorption capacity for Cr(III)-EDTA than Cr(III).•High salt reduced Cr(III) adsorption but improved Cr(III)-EDTA adsorption.•Ternary complex formation contributed to the enhanced Cr(III)-EDTA adsorption.•Fe3O4@C@DETA could be regenerated and the adsorbent can be reused.
The organic–inorganic hybrid lead trihalide perovskites have been emerging as the most attractive photovoltaic materials. As regulated by Shockley–Queisser theory, a formidable materials science ...challenge for improvement to the next level requires further band-gap narrowing for broader absorption in solar spectrum, while retaining or even synergistically prolonging the carrier lifetime, a critical factor responsible for attaining the near-band-gap photovoltage. Herein, by applying controllable hydrostatic pressure, we have achieved unprecedented simultaneous enhancement in both band-gap narrowing and carrier-lifetime prolongation (up to 70% to ∼100% increase) under mild pressures at ∼0.3 GPa. The pressure-induced modulation on pure hybrid perovskites without introducing any adverse chemical or thermal effect clearly demonstrates the importance of band edges on the photon–electron interaction and maps a pioneering route toward a further increase in their photovoltaic performance.
This paper presents the interaction of benzoapyrene (BaP) with Cu(II)-montmorillonite to investigate the formation, evolution and potential toxicity of environmentally persistent free radicals ...(EPFRs) under dark and visible light irradiation conditions. Degradation of BaP and the generated transformative products on clay mineral are monitored by gas chromatography–mass spectrometry (GC–MS) technique. Hydroxyl-BaP and BaP-diones are observed during the transformation of BaP under dark condition. BaP-3,6-dione and BaP-6,12-dione are the main products under visible light irradiation. BaP transformation is accompanied by the formation of EPFRs, which are quantified by electron paramagnetic resonance (EPR) spectroscopy. With increasing reaction time, the concentrations of the produced EPFRs are initially increased and then gradually decrease to an undetectable level. The deconvolution results of EPR spectra reveal formation of three types of organic radicals (carbon-centered radicals, oxygen-centered radicals, and carbon-centered radicals with a conjugated oxygen), which also co-exist. Correspondingly, visible-light irradiation promotes the formation and the decay of these EPFRs. The produced BaP-type EPFRs induce the generation of reactive oxygen species (ROS), such as superoxide (O2–) and hydroxide radicals (OH), which may cause oxidative stress to cells and tissues of organisms. The toxicity of degradation products is evaluated by the livability of human gastric epithelial GES-1cells. The toxicity is initially increased and then decreases with the elapsed reaction time, which correlates with the evolution of EPFRs concentrations. The present work provides direct evidence that the formation of EPFRs in interaction of PAHs with metal-contaminated clays may result in negative effects to human health.
Display omitted
•Cu-clay has great potential for catalytic BaP degradation in dark/light conditions.•The formation and decay of EPFR and ROS were monitored as a function of reaction time.•Potential evolution mechanism of BaP on Cu-smectite was systematically explored.•Toxicity of the generated radicals was examined against epithelial GES-1 cells.
In this work, Pt nanoflowers deposited on highly ordered TiO2 nanotube arrays (TNTs) by modification of reduced graphene oxide (RGO) nanostructures have been synthesized. The ternary complex ...(Pt-TNTs/RGO) displays efficient electrocatalytic performance toward methanol oxidation in alkaline medium. The electrochemical impedance spectroscopy (EIS) and responsive photocurrent results indicate that the presence of graphene could effectively promote charge separation during electrocatalytic process. Interestingly, with assistance of visible light illumination, the electrocatalytic activity and stability of the ternary complex electrode toward methanol oxidation are distinctly improved. Both electro- and photo-catalytic processes for methanol oxidation contribute to the enhanced catalytic performance and stability. Moreover, the ternary electrode also displays efficient photoelectrocatalytic degradation of methylene blue (MB) under visible light illumination. The present work sheds light on developing highly efficient and long-term stability catalysts for methanol oxidation with assistance of visible-light illumination.
In recent years, there has been a wide research in supported single-atom catalysts (SACs), which contain only isolated individual metal atoms dispersed on an appropriate support or coordinated with ...the surface atoms of the support. The SACs exhibit many fascinating characteristics including high activity, selectivity, and maximum atomic utilization. These characteristics arise from the low coordination status, quantum size effect, and the strong metal–support interaction, which have proved to be very powerful in many typical heterogeneous catalysis field including oxidation, hydrogenation, the water–gas shift reaction, methanol steam reforming, electrocatalysis, and photocatalysis. In this review, we summarized the recent progress in synthesis, characterizations, properties, and applications of SACs.
Amine groups play significant roles in polymeric composites for heavy metals removal. However, generating a composite with a large number of functional and stable amine groups based on clay is still ...a challenge. In this work, a new amine-functionalized adsorbent based on acid-activated vermiculite (a-Verm) was prepared by organic modification of silane coupling agent as bridge, followed by in situ polymerization of acrylamide (AM) and further grafting of triethylene tetramine (TETA). The obtained polymeric composite g-PAM/OVerm was characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Fourier transform infrared (FTIR), thermal analysis (TG/DTG), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyses, confirming that amine groups were successfully grafted onto the surface of Verm. The efficacy g-PAM/OVerm for removing Pb(II) was tested. The adsorption equilibrium data on g-PAM/OVerm was in good accordance with the Langmuir adsorption isotherms, and the adsorption maximal value of Pb(II) was 219.4 mg·g
. The adsorption kinetic data fit the pseudo-second-order kinetic model well. Additionally, g-PAM/OVerm has better selectivity for Pb(II) ion in comparison with Zn(II), Cd(II) and Cu(II) ions. The present work shows that g-PAM/OVerm holds great potential for removing Pb(II) from wastewater, and provides a new and efficient method for the removal of heavy metal ions from industrial wastewater.
•Low-molecular-weight organic acids have significant influence on PAHs photolysis.•Chelating ability of LMWOAs with Fe are critical to their roles in Phe photolysis.•Presence of oxalic and malic ...acids favor Phe photodegradation on Fe(III)–clay.•EDTA or nitrilotriacetic acid inhibits both Fe(II) formation and Phe photolysis.•Reductive CO2− radicals involved in Phe photodegradation are supported by EPR.
The photolysis of polycyclic aromatic hydrocarbons (PAHs) is potentially an important process for its transformation and fate on contaminated soil surfaces. In this study, phenanthrene is employed as a model to explore PAH photodegradation with the assistance of Fe(III)–smectite under visible-light while focusing on roles played by five low-molecular-weight organic acids (LMWOAs), i.e., malic acid, oxalic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), and nitrilotriacetic acid. Our results show that oxalic acid is most effective in promoting the photodegradation of phenanthrene, while only a slight increase in the rate of phenanthrene photodegradation is observed in the presence of malic acid. Electron paramagnetic resonance experiments confirm the formation of CO2− radicals in the presence of malic and oxalic acid, which provides strong evidence for generating OH and subsequent photoreaction pathways. The presence of EDTA or nitrilotriacetic acid significantly inhibits both Fe(II) formation and phenanthrene photodegradation because these organic anions tend to chelate with Fe(III), leading to decreases in the electron-accepting potential of Fe(III)–smectite and a weakened interaction between phenanthrene and Fe(III)–smectite. These observations provide valuable insights into the transformation and fate of PAHs in the natural soil environment and demonstrate the potential for using some LMWOAs as additives for the remediation of contaminated soil.
Excessive Cu2+ intake can cause neurological disorders (e.g. Wilson’s disease) and adversely affect the gastrointestinal, liver, and kidney organs. The presence of Cu2+ is strongly linked to the ...emergence and progression of Wilson's disease (WD), and accurately measuring the amount of copper is a crucial step in diagnosing WD at an early stage in a clinical setting. In this work, CQDs were fabricated through a facile technique as a novel fluorescence-based sensing platform for detecting Cu(II) in aqueous solutions, and in the serum samples of healthy and affected individuals by WD. The CQDs interact with Cu(II) ions to produce Turn-on and Turn-off states at nano-molar and micro-molar levels, respectively, with LODs of 0.001 µM and 1 µM. In fact, the Cu2+ ions can act like a bridge between two CQDs by which the charge and electron transfer between the CQDs may increase, possibly can have significant effects on the spectroscopic features of the CQDs. To the best of our knowledge, this is the first reported research that can detect Cu(II) at low levels using two different complexation states, with promising results in testing serum. The potential of the sensor to detect Cu(II) was tested on serum samples from healthy and affected individuals by WD, and compared to results obtained by ICP-OES. Astonishingly, the results showed an excellent correlation between the measured Cu(II) levels using the proposed technique and ICP-OES, indicating the high potential of the fluorimetric CQD-based probe for Cu(II) detection. The accuracy, sensitivity, selectivity, high precision, accuracy, and applicability of the probe toward Cu(II) ions make it a potential diagnostic tool for Wilson's disease in a clinical setting.
PDF
![Interaction of benzo[a]pyre...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/0160-4120_1873-6750/small "Interaction of benzo[a]pyrene with Cu(II)-montmorillonite: Generation and toxicity of environmentally persistent free radicals and reactive oxygen species")
