Changes in Novel Biomarkers for Protein Oxidation in Pork Patties under Different Cooking Methods.

The aim of this study was to assess the effectiveness of different biomarkers to identify the levels of protein oxidation in pork patties induced by assorted cooking methods. To achieve this purpose, pork patties prepared from longissimus dorsi were cooked using three methods (frying, steaming, and roasting) at different internal temperatures (60, 70, 80, and 90 °C). Traditional biomarkers including total carbonyl and total thiol and novel biomarkers including α-aminoadipic semialdehyde (AAS) and lysinonorleucine (LNL) were determined. Results demonstrated that total thiol and AAS were the most successful biomarkers in distinguishing the three cooking methods in relation to protein oxidation, with AAS being the most sensitive. Moreover, as indicated by the biomarkers of total thiol and AAS, frying caused the highest level of protein oxidation, while steaming resulted in the lowest level when pork patties were cooked to the internal temperatures of 70 or 80 °C.

Creation of Interfacial S4 -Sn-N2 Electron Pathways for Efficient Light-Driven Hydrogen Evolution.

Establishing effective charge transfer channels between two semiconductors is key to improving photocatalytic activity. However, controlling hetero-structures in situ and designing binding modes pose significant challenges. Herein, hydrolytic SnCl2 ·2H2 O is selected as the metal source and loaded in situ onto a layered carbon nitriden supramolecular precursor. A composite photocatalyst, S4 -Sn-N2 , with electron pathways of SnS2 and tubular carbon nitriden (TCN) is prepared through pyrolysis and vulcanization processes. The contact interface of SnS2 -TCN is increased significantly, promoting the formation of S4 -Sn-N2 micro-structure in a Z-scheme charge transfer channel. This structure accelerates the separation and transport of photogenerated carriers, maintains the stronger redox ability, and improves the stability of SnS2 in this series of heterojunctions. Therefore, the catalyst demonstrated exceptional photocatalytic hydrogen production efficiency, achieving a reaction rate of 86.4 µmol h-1 , which is 3.15 times greater than that of bare TCN.

Pathologic vs. protective roles of hypoxia-inducible factor 1 in RPE and photoreceptors in wet vs. dry age-related macular degeneration.

It has previously been reported that antioxidant vitamins can help reduce the risk of vision loss associated with progression to advanced age-related macular degeneration (AMD), a leading cause of visual impairment among the elderly. Nonetheless, how oxidative stress contributes to the development of choroidal neovascularization (CNV) in some AMD patients and geographic atrophy (GA) in others is poorly understood. Here, we provide evidence demonstrating that oxidative stress cooperates with hypoxia to synergistically stimulate the accumulation of hypoxia-inducible factor (HIF)-1α in the retinal pigment epithelium (RPE), resulting in increased expression of the HIF-1-dependent angiogenic mediators that promote CNV. HIF-1 inhibition blocked the expression of these angiogenic mediators and prevented CNV development in an animal model of ocular oxidative stress, demonstrating the pathological role of HIF-1 in response to oxidative stress stimulation in neovascular AMD. While human-induced pluripotent stem cell (hiPSC)-derived RPE monolayers exposed to chemical oxidants resulted in disorganization and disruption of their normal architecture, RPE cells proved remarkably resistant to oxidative stress. Conversely, equivalent doses of chemical oxidants resulted in apoptosis of hiPSC-derived retinal photoreceptors. Pharmacologic inhibition of HIF-1 in the mouse retina enhanced-while HIF-1 augmentation reduced-photoreceptor apoptosis in two mouse models for oxidative stress, consistent with a protective role for HIF-1 in photoreceptors in patients with advanced dry AMD. Collectively, these results suggest that in patients with AMD, increased expression of HIF-1α in RPE exposed to oxidative stress promotes the development of CNV, but inadequate HIF-1α expression in photoreceptors contributes to the development of GA.

Protein carbonylation and structural changes in porcine myofibrillar protein exposed to metal ion-H2O2-ascorbate and linoleic acid-lipoxidase oxidizing systems.

The present study aimed to compare two oxidizing systems commonly present in meat for their influence on protein oxidation patterns, with emphasis on the specific lysine-derived markers for protein carbonylation (α-aminoadipic semialdehyde, AAS; lysinonorlucine, LNL) and their relationships with the common markers for protein oxidation. For this purpose, pork myofibrillar proteins (MFP, 5 mg/mL) were suspended in 0.6 M NaCl (pH 7.5) and incubated at 4 ℃ for 24 h with two oxidizing systems: (1) a metal-catalyzed oxidizing system (MOS: 10 µM FeCl3, 100 µM ascorbic acid, and 0-10 mmol/L H2O2), (2) a linoleic acid - lipoxidase oxidizing system (LOS: 7500 units of lipoxidase/mL, and 0-10 mM linoleic acid). Results showed that the amounts of AAS and LNL in both MOS- and LOS-oxidized MFP was proportional to the oxidant concentrations (H2O2 or linoleic acid), while the formation of total carbonyl and total thiol also exhibited similar oxidant-dose-dependent patterns. Meanwhile, the α-helix contents of MFP declined with oxidant concentrations irrespective of the oxidizing systems. The reducing SDS-PAGE revealed that the myosin heavy chain band started to diminish at high H2O2 concentration (5 and 10 mM) in MOS whereas at low level of linoleic acid (0.5 mM) in LOS. Overall, these results demonstrated both oxidizing systems could be involved in the formation of AAS and LNL, and that the generation of AAS and LNL can be used as reliable markers for protein oxidation, but also might be directly involved in protein structural changes and then contribute to the alternations of protein functionality.

Targeting hypoxia-inducible factors with 32-134D safely and effectively treats diabetic eye disease in mice.

Many patients with diabetic eye disease respond inadequately to anti-VEGF therapies, implicating additional vasoactive mediators in its pathogenesis. We demonstrate that levels of angiogenic proteins regulated by HIF-1 and -2 remain elevated in the eyes of people with diabetes despite treatment with anti-VEGF therapy. Conversely, by inhibiting HIFs, we normalized the expression of multiple vasoactive mediators in mouse models of diabetic eye disease. Accumulation of HIFs and HIF-regulated vasoactive mediators in hyperglycemic animals was observed in the absence of tissue hypoxia, suggesting that targeting HIFs may be an effective early treatment for diabetic retinopathy. However, while the HIF inhibitor acriflavine prevented retinal vascular hyperpermeability in diabetic mice for several months following a single intraocular injection, accumulation of acriflavine in the retina resulted in retinal toxicity over time, raising concerns for its use in patients. Conversely, 32-134D, a recently developed HIF inhibitor structurally unrelated to acriflavine, was not toxic to the retina, yet effectively inhibited HIF accumulation and normalized HIF-regulated gene expression in mice and in human retinal organoids. Intraocular administration of 32-134D prevented retinal neovascularization and vascular hyperpermeability in mice. These results provide the foundation for clinical studies assessing 32-134D for the treatment of patients with diabetic eye disease.

HIF-1α accumulation in response to transient hypoglycemia may worsen diabetic eye disease.

Tight glycemic control (TGC), the cornerstone of diabetic management, reduces the incidence and progression of diabetic microvascular disease. However, TGC can also lead to transient episodes of hypoglycemia, which have been associated with adverse outcomes in patients with diabetes. Here, we demonstrate that low glucose levels result in hypoxia-inducible factor (HIF)-1-dependent expression of the glucose transporter, Glut1, in retinal cells. Enhanced nuclear accumulation of HIF-1α was independent of its canonical post-translational stabilization but instead dependent on stimulation of its translation and nuclear localization. In the presence of hypoxia, this physiologic response to low glucose resulted in a marked increase in the secretion of the HIF-dependent vasoactive mediators that promote diabetic retinopathy. Our results provide a molecular explanation for how early glucose control, as well as glycemic variability (i.e., oscillating serum glucose levels), contributes to diabetic eye disease. These observations have important implications for optimizing glucose management in patients with diabetes.

Aflibercept more effectively weans patients with neovascular age-related macular degeneration off therapy compared with bevacizumab.

BACKGROUNDStudies assessing the efficacy of therapies for neovascular age-related macular degeneration (nvAMD) have demonstrated that aflibercept may have a longer treatment interval than its less-expensive alternative, bevacizumab. However, whether this benefit justifies the additional cost of aflibercept remains under debate. We have recently reported that a treat-and-extend-pause/monitor approach can be used to successfully wean 31% of patients with nvAMD off anti-VEGF therapy. Here, we examined whether the choice of therapy influences the outcomes of this approach.METHODSIn this retrospective analysis, 122 eyes of 106 patients with nvAMD underwent 3 consecutive monthly injections with either aflibercept (n = 70) or bevacizumab (n = 52), followed by a treat-and-extend protocol, in which the decision to extend the interval between treatments was based on visual acuity, clinical exam, and the presence or absence of fluid on optical coherence tomography. Eyes that remained stable 12 weeks from their prior treatment were given a 6-week trial of holding further treatment, followed by quarterly monitoring. Treatment was resumed for worsening vision, clinical exam, or optical coherence tomography findings.RESULTSAt the end of 1 year, eyes receiving bevacizumab had similar vision but required more injections (8.7 ± 0.3 treatments vs. 7.2 ± 0.3 treatments) compared with eyes receiving aflibercept. However, eyes treated with aflibercept were almost 3 times more likely to be weaned off treatment (43% vs. 15%) compared with eyes treated with bevacizumab at the end of 1 year.CONCLUSIONThese observations expose an advantage of aflibercept over bevacizumab and have important clinical implications for the selection of therapy for patients with nvAMD.FUNDINGThis work was supported by the National Eye Institute, NIH grants R01EY029750 and R01EY025705, Research to Prevent Blindness, the Alcon Young Investigator Award from the Alcon Research Institute, and the Branna and Irving Sisenwein Professorship in Ophthalmology.

Selective detection of trace carbon monoxide at room temperature based on CuO nanosheets exposed to (111) crystal facets.

In recent years, carbon monoxide (CO) intoxication incidents occur frequently, and the sensitive detection of CO is particularly significant. At present, most reported carbon monoxide (CO) sensors meet the disadvantage of high working temperature. It is always a challenge to realize the sensitive detection of carbon monoxide at room temperature. In this study, CuO nanosheets exposed more (111) active crystal facets and oxygen vacancy defects were synthesized by a simple and environmentally friendly one-step hydrothermal method. The sensor has good comprehensive gas sensing performance, compared with other sensors that can detect CO at room temperature. The response value to 100 ppm CO at room temperature is as high as 39.6. In addition, it also has excellent selectivity, low detection limit (100 ppb), good reproducibility, moisture resistance and long-term stability (60 days). This excellent gas sensing performance is attributed to the special structural characteristics of 2D materials and the synergistic effect of more active crystal facets exposed on the crystal surface and oxygen vacancy defects. Therefore, it is expected to become a promising sensitive material for rapid and accurate detection of trace CO gas under low energy consumption, reduce the risk of poisoning, and then effectively protect human life safety.

Characterization of core fucosylation via sequential enzymatic treatments of intact glycopeptides and mass spectrometry analysis.

Core fucosylation of N-linked glycoproteins has been linked to the functions of glycoproteins in physiological and pathological processes. However, quantitative characterization of core fucosylation remains challenging due to the complexity and heterogeneity of N-linked glycosylation. Here we report a mass spectrometry-based method that employs sequential treatment of intact glycopeptides with enzymes (STAGE) to analyze site-specific core fucosylation of glycoproteins. The STAGE method utilizes Endo F3 followed by PNGase F treatment to generate mass signatures for glycosites that are formerly modified by core fucosylated N-linked glycans. We benchmark the STAGE method and use it to characterize site specific core fucosylation of glycoproteins from human hepatocellular carcinoma and pancreatic ductal adenocarcinoma, resulting in the identification of 1130 and 782 core fucosylated glycosites, respectively. These results indicate that our STAGE method enables quantitative characterization of core fucosylation events from complex protein mixtures, which may benefit our understanding of core fucosylation functions in various diseases.

Achieving Electronic Engineering of Vanadium Oxide-Based 3D Lithiophilic Sandwiched-Aerogel Framework for Ultrastable Lithium Metal Batteries.

Lithium (Li) metal is one of the most promising anode materials for the next-generation batteries, which owns superior specific capacity and energy density. Unfortunately, lithium dendrites that is formed during the charging/discharging process tends to induce capacity degradation and thus short lifespan. In this study, the vanadium oxide (V2O5) and nitrogen-doped vanadium oxide (N-V2O3, N-VO0.9)-modified three-dimensional (3D) reduced graphene oxide ((N)-VOx@rGO) with tunable electronic properties are demonstrated to enable the dendrite-free Li deposition. The soft lithiophilic rGO as the scaffold can provide sufficient void space for Li storage. Meanwhile, the rigid (N)-VOx uniformly anchored on rGO can perfectly maintain the 3D structure, which is crucial for Li to enter the inner space of the 3D framework. Consequently, the (N)-VOx@rGO electrodes achieve dendrite-free electrodeposition under the multifarious deposition capacity and current densities. Compared with the bare lithium electrodes, the asymmetrical cells of (N)-VOx@rGO anode can cycle stably up to 400 h at 2 mA cm-2 current density, together with a low nucleation overpotential of ∼20 mV.

ANGPTL4 influences the therapeutic response of patients with neovascular age-related macular degeneration by promoting choroidal neovascularization.

Most patients with neovascular age-related macular degeneration (nvAMD), the leading cause of severe vision loss in elderly US citizens, respond inadequately to current therapies targeting a single angiogenic mediator, vascular endothelial growth factor (VEGF). Here, we report that aqueous fluid levels of a second vasoactive mediator, angiopoietin-like 4 (ANGPTL4), can help predict the response of patients with nvAMD to anti-VEGF therapies. ANGPTL4 expression was higher in patients who required monthly treatment with anti-VEGF therapies compared with patients who could be effectively treated with less-frequent injections. We further demonstrate that ANGPTL4 acts synergistically with VEGF to promote the growth and leakage of choroidal neovascular (CNV) lesions in mice. Targeting ANGPTL4 expression was as effective as targeting VEGF expression for treating CNV in mice, while simultaneously targeting both was more effective than targeting either factor alone. To help translate these findings to patients, we used a soluble receptor that binds to both VEGF and ANGPTL4 and effectively inhibited the development of CNV lesions in mice. Our findings provide an assay that can help predict the response of patients with nvAMD to anti-VEGF monotherapy and suggest that therapies targeting both ANGPTL4 and VEGF will be a more effective approach for the treatment of this blinding disease.

Controllable construction of ZnFe2O4-based micro-nano heterostructure for the rapid detection and degradation of VOCs.

Micro-nano heterogeneous oxides have received extensive attention due to their distinctive physicochemical properties. However, it is a challenge to prepare the hierarchical multicomponent metal oxide nanomaterials with abundant heterogeneous interfaces in a controllable way. In this work, the effective construction of the heterogeneous structure of the material is achieved by regulating the ratio of metal salts under thermal solvent condition. Three-dimensional spheres (ZnFe2O4) constructed by zero-dimensional ultra-small nanoparticles, in particular three-dimensional hollow sea urchin spheres (ZnO/ZnFe2O4) constructed by one-dimensional nanorods and three-dimensional hydrangeas (α-Fe2O3/ZnFe2O4) assembled by two-dimensional nanosheets were obtained. The two composite materials contain a large number of heterojunctions, which enhances the sensitivity of material to volatile organic compounds gas. Among them, the α-Fe2O3/ZnFe2O4 composite shows the best sensing performance for VOCs. For example, its response to 100 ppm acetone reaches 142 at 170 °C with the response time shortened to 3 s and the detection limit falling to 10 ppb. Meanwhile, the composite material presents a degradation rate of more than 90% for VOCs at a flow rate of 20 mL/min at 170 °C. In addition, the sensing and sensitivity mechanism of the composite material are studied in detail by combining GC-MS, XPS with UV diffuse reflectance tests.

A Unique Fe-N4 Coordination System Enabling Transformation of Oxygen into Superoxide for Photocatalytic CH Activation with High Efficiency and Selectivity.

Selective oxidation of CH bonds is one of the most important reactions in organic synthesis. However, activation of the α-CH bond of ethylbenzene by use of photocatalysis-generated superoxide anions (O2 •- ) remains a challenge. Herein, the formation of individual Fe atoms on polymeric carbon nitride (CN), that activates O2  to create O2 •- for facilitating the reaction of ethylbenzene to form acetophenone, is demonstrated. By utilizing density functional theory and materials characterization techniques, it is shown that individual Fe atoms are coordinated to four N atoms of CN and the resultant low-spin Fe-N4  system (t2g 6 eg 0 ) is not only a great adsorption site for oxygen molecules, but also allows for fast transfer of electrons generated in the CN framework to adsorbed O2 , producing O2 •- . The oxidation reaction of ethylbenzene triggered by O2 •- ions turns out to have a high conversion rate of 99% as well as an acetophenone selectivity of 99%, which can be ascribed to a novel reaction pathway that is different from the conventional route involving hydroxyl radicals and the production of phenethyl alcohol. Furthermore, it possesses great potential for other CH activation reactions besides ethylbenzene oxidation.

Aqueous proteins help predict the response of patients with neovascular age-related macular degeneration to anti-VEGF therapy.

BackgroundTo reduce the treatment burden for patients with neovascular age-related macular degeneration (nvAMD), emerging therapies targeting vascular endothelial growth factor (VEGF) are being designed to extend the interval between treatments, thereby minimizing the number of intraocular injections. However, which patients will benefit from longer-acting agents is not clear.MethodsEyes with nvAMD (n = 122) underwent 3 consecutive monthly injections with currently available anti-VEGF therapies, followed by a treat-and-extend protocol. Patients who remained quiescent 12 weeks from their prior treatment entered a treatment pause and were switched to pro re nata (PRN) treatment (based on vision, clinical exam, and/or imaging studies). Proteomic analysis was performed on aqueous fluid to identify proteins that correlate with patients' response to treatment.ResultsAt the end of 1 year, 38 of 122 eyes (31%) entered a treatment pause (≥30 weeks). Conversely, 21 of 122 eyes (17%) failed extension and required monthly treatment at the end of year 1. Proteomic analysis of aqueous fluid identified proteins that correlated with patients' response to treatment, including proteins previously implicated in AMD pathogenesis. Interestingly, apolipoprotein-B100 (ApoB100), a principal component of drusen implicated in the progression of nonneovascular AMD, was increased in treated patients who required less frequent injections. ApoB100 expression was higher in AMD eyes compared with controls but was lower in eyes that develop choroidal neovascularization (CNV), consistent with a protective role. Accordingly, mice overexpressing ApoB100 were partially protected from laser-induced CNV.FundingThis work was supported by the National Eye Institute, National Institutes of Health grants R01EY029750, R01EY025705, and R01 EY27961; the Research to Prevent Blindness, Inc.; the Alcon Research Institute; and Johns Hopkins University through the Robert Bond Welch and Branna and Irving Sisenwein professorships in ophthalmology.ConclusionAqueous biomarkers could help identify patients with nvAMD who may not require or benefit from long-term treatment with anti-VEGF therapy.

Fast detection of NO2 by porous SnO2 nanotoast sensor at low temperature.

In order to challenge high working temperature, low response and low selectivity of present NO2 sensor, porous SnO2 nanotoasts with a large surface area (79.94 m2/g) were synthesized. Thick film sensors fabricated by the SnO2 nanotoasts exhibited a high response to NO2 gas operating at room temperature. Excellent performance for NO2 sensing gas at 50 °C, included the high response of 105.2 (10 ppm), low detection limitation of 0.1 ppm, fast response within 10 s, and wide range of 0.1-10 ppm (R2 = 0.9931). These sensors also demonstrated perfect selectivity, moisture resistance and 90 days of long-term stability. SnO2 nanotoasts sensor has excellent detection ability in actual detection. The superior response of porous SnO2 nanotoasts towards NO2 was attributed to the special porous structure with large specific surface area and oxygen vacancies in sensing material, which helped adsorption of the target gas molecules onto the sensing surfaces and transfer of the charge.

Ionic liquid([C12mim][PF6])-assisted synthesis of TiO2 /Ti2O (PO4)2 nanosheets and the chemoresistive gas sensing of trimethylamine.

The architecture of PO43- modified 2D TiO2 nanosheets was constructed by ionic liquids (ILs)-assisted hydrothermal method. The nanosheet structure can be regulated by the addition of different amount of ionic liquid. Using the composite nanosheets  a chemoresistive gas sensor was prepared for trimethylamine (TMA) detection. Most reported TMA sensors need to be operated at a relatively high operating temperature, but in this paper, the as-synthesized PO43--modified 2D TiO2/Ti2O(PO4)2 nanosheet sensor has high response (S = 87.46), short response time (14.6 s), and good reproducibility to 100 ppm TMA gas, when the temperature is 170 °C. In contrast to the single-phase TiO2 sensor, the gas-sensing property of the composite one is obviously enhanced. Moreover, its response shows excellent linear relationship with TMA concentration from 0.2 to 500 ppm, and a detection limit of 0.2 ppm. The TMA detection mechanism was investigated by analyzing the changes of the surface adsorption oxygen content by XPS and gaseous products using gas chromatography after the sensor was in contact with TMA.

Novel Two-Dimensional WO3/Bi2W2O9 Nanocomposites for Rapid H2S Detection at Low Temperatures.

Compared with single-component metal oxides, multicomponent metal oxides show good gas sensing performance in the field of gas sensing, but they still need to be further improved in terms of rapid response. In this paper, a two-dimensional flaky WO3/Bi2W2O9 composite material with a thickness of about 32.3 nm was synthesized by a simple solvothermal method. The composite has good sensing performance and selectivity toward H2S. When the operating temperature is as low as 92 °C, the response to 100 ppm H2S reaches 84.18, and the response time is 2 s, which is extremely fast due to the open system of the two-dimensional nanosheet. A combination of gas chromatography-mass spectrometry (GC-MS) and X-ray photoelectron spectroscopy (XPS) is used to analyze the changes of H2S and the surface chemistry of WO3/Bi2W2O9 composite materials; the sensing mechanism of H2S was studied by a Kelvin probe and UV diffuse reflection. Compared with the pure phase WO3 and Bi2W2O9, good gas sensing properties of the WO3/Bi2W2O9 composite may be due to its unique heterostructure. This is the first application of WO3/Bi2W2O9 in the field of gas sensing and is of great significance for the rapid detection of H2S at low temperatures for multicomponent metal oxides.

Zebrafish Crb1, Localizing Uniquely to the Cell Membranes around Cone Photoreceptor Axonemes, Alleviates Light Damage to Photoreceptors and Modulates Cones' Light Responsiveness.

The crumbs (crb) apical polarity genes are essential for the development and functions of epithelia. Adult zebrafish retinal neuroepithelium expresses three crb genes (crb1, crb2a, and crb2b); however, it is unknown whether and how Crb1 differs from other Crb proteins in expression, localization, and functions. Here, we show that, unlike zebrafish Crb2a and Crb2b as well as mammalian Crb1 and Crb2, zebrafish Crb1 does not localize to the subapical regions of photoreceptors and Müller glial cells; rather, it localizes to a small region of cone outer segments: the cell membranes surrounding the axonemes. Moreover, zebrafish Crb1 is not required for retinal morphogenesis and photoreceptor patterning. Interestingly, Crb1 promotes rod survival under strong white light irradiation in a previously unreported non--cell-autonomous fashion; in addition, Crb1 delays UV and blue cones' chromatin condensation caused by UV light irradiation. Finally, Crb1 plays a role in cones' responsiveness to light through an arrestin-translocation-independent mechanism. The localization of Crb1 and its functions do not differ between male and female fish. We conclude that zebrafish Crb1 has diverged from other vertebrate Crb proteins, representing a neofunctionalization in Crb biology during evolution.SIGNIFICANCE STATEMENT Apicobasal polarity of epithelia is an important property that underlies the morphogenesis and functions of epithelial tissues. Epithelial apicobasal polarity is controlled by many polarity genes, including the crb genes. In vertebrates, multiple crb genes have been identified, but the differences in their expression patterns and functions are not fully understood. Here, we report a novel subcellular localization of zebrafish Crb1 in retinal cone photoreceptors and evidence for its new functions in photoreceptor maintenance and light responsiveness. This study expands our understanding of the biology of the crb genes in epithelia, including retinal neuroepithelium.

TiO2-on-C3N4 double-shell microtubes: In-situ fabricated heterostructures toward enhanced photocatalytic hydrogen evolution.

Structural design, doping, and construction of heterojunctions are effective strategies for producing highly efficient photocatalytic materials. Herein, N-doped TiO2 was formed on hexagonal C3N4 tube through in-situ hydrolysis of a Ti source on a supramolecular precursor, followed by thermal treatment. As a result, a double-shell microtube, C3N4@TiO2 heterostructure was fabricated. It was worth noting that the supramolecular precursor was prepared from melamine and cyanuric acid, which not only served as a template for the double-shell tubular structure, but also provided nitrogen for the doping of TiO2. The photocatalytic efficiency of C3N4@TiO2 was investigated by conducting hydrogen production experiments. The hydrogen production rate of C3N4@TiO2 was measured to be 10.1 mmol h-1 g-1, which is 4 times and 15 times that of C3N4 and TiO2, respectively. The improved photocatalytic activity of C3N4@TiO2 can be ascribed to (1) the tubular structure that provides a large number of reaction sites and enhances mass transport, (2) the heterojunction that is beneficial to charge separation, and (3) doping of TiO2 with nitrogen which extends its optical absorption range to visible light. This work demonstrates a facile method for synthesizing a highly efficient photocatalyst towards hydrogen evolution by modifying its structure and chemical composition as well as forming a heterojunction.

Promoting the spatial charge separation by building porous ZrO2@TiO2 heterostructure toward photocatalytic hydrogen evolution.

The robust photocatalytic hydrogen evolution (PHE) from water needs an effective photogenerated charge spatial separation and enough contact between reactant and catalyst, but the synthesis of catalysts with the characteristics remains a challenge. Herein, we report the design of core-shell heterostructure consisted of thin TiO2 layer uniformly coated on porous ZrO2 polyhedron for effective PHE. In this system, UiO-66-NH2, one of popular MOF with Zr as metal node, has been chosen as the precursor template due to its plentiful pores, uniform morphology, as well as the rich NH2 groups. Our results show that Ti precursor can uniformly coat on UiO-66-NH2, by means of interaction of tetrabutyl titanate (TBT) with -NH3 in UiO-66-NH2. Followed by the calcination, the Ti precursor and UiO-66-NH2 can be converted into ZrO2 and TiO2, respectively, thus leading to the formation of ZrO2@TiO2 core-shell heterostructure. The ZrO2@TiO2-500 has the high specific surface area of 52.4 m2 g-1. Besides, the intimate contact of TiO2 shell with ZrO2 core facilitates the separation and migration of photoinduced carriers, exposing more active sites for the surface photocatalytic hydrogen evolution reaction. The spectrum and electrochemical characterization further exhibit the extended life of photon-generated carrier and easy mass transfer. The optimized ZrO2@TiO2-500 shows enhanced photocatalytic rate of 39.7 mmol h-1 g-1, much higher than those of ZrO2 (0.8 mmol h-1 g-1) and TiO2 (7.6 mmol h-1 g-1).