Enhanced photodegradation of tetracycline in wastewater and conversion of CO2 by solar light assisted ZnO/g-C3N4.

Synthesized graphitic carbon nitride-based (CN) heterojunction photocatalysts are considered as a promising material for photodegradation of organic compounds and CO2 conversion. In this work, ZnO-loaded g-C3N4 (ZnO/CN) heterojunction photocatalyst was investigated for the enhanced photooxidation of tetracycline (TC) and CO2 conversion . After modification, the photocatalysts showed an improvement in the light absorption range and the photogenerated separation rate of electron/hole due to the heterojunction structure of ZnO/CN. The degradation rate of TC was found to be 92.6% within 60 min, while CO production rate was 7.68 µmol/g/h. The rate constants of TC by using ZnO/CN were 0.0812, 0.0539, 0.0336, 0.0249, and 0.0185 min-1, corresponding to the TC level of 1, 10, 30, 50, and 100 mg/L, respectively. The photodegradation rate of TC by ZnO/CN was 5 times higher than that of CN, demonstrating the advantage of heterojunction photocatalyst. The modified ZnO/CN exhibited superior degradation performance of TC and higher CO2 conversion rate than those of unmodified CN. It also exhibited high stability with 82% removal efficiency of TC at the 6th run and the CO2 conversion rate of 71% after reused 5 times. The heterojunction ZnO/CN can be utilized as an efficient material for various photocatalytic applications.

Enhanced Room-Temperature Ethanol Detection by Quasi 2D Nanosheets of an Exfoliated Polymeric Graphitized Carbon Nitride Composite-Based Patterned Sensor.

A novel room-temperature gas sensor composed of polymeric graphitic carbon nitride composite was fabricated and used for the detection of ethanol vapor under ambient conditions. Polymeric carbon nitride (PCN) microstructures composed of fluffy nanosheets were synthesized via a thermal polycondensation mechanism using melamine as the precursor, followed by vigorous chemical exfoliation. These sheet-like microstructures were employed as active materials in the form of composites, along with carbon paste consisting of graphite nanoplatelets and carbon black. The active sensing layer was fabricated on a PET sheet and assembled on an interdigitated gold electrode. The as-fabricated sensor exhibited excellent sensing efficiency (>100% response at 10 ppm) along with high selectivity and stability. In particular, for ultralow concentrations such as 1 ppm (>10% response), this resistive-based sensor exhibited a swift response time provided under ambient conditions. The exfoliated PCN composite sensor was found to be working with appreciable efficiency at moderate relative humidity (%) with the least fluctuation in response signals also demonstrating long-term stability for 30 days with consistent response signals.

Visible-light photocatalysis of Ag-doped graphitic carbon nitride for photodegradation of micropollutants in wastewater.

This work reports on graphitic carbon nitride (C3N4) modified with silver to investigate its visible-light-driven photocatalysis for decomposition of micropollutants in wastewater. Various characterization methods were conducted to examine the physico-chemical properties of Ag-doped C3N4 (Ag-C3N4) photocatalyst. The results from structural, morphological, and surface chemical analysis indicated that C3N4 was successfully doped with Ag. Photoluminescence and transient photocurrent density studies revealed that the recombination rate of electron-hole pairs was reduced, leading to the enhancement of photocatalytic activities of the photocatalyst. Ag-C3N4 showed high photocatalytic performance for photodegradation of our target micropollutant, bisphenol A (BA). It could completely remove BA in 1 h with kinetic constant 6.2 times higher than that of the undoped C3N4 photocatalyst. Recycling test and the assessment of the photocatalyst in wastewater further confirmed the excellent stability and applicability of the Ag-C3N4 photocatalyst. This work could provide a new solution to the practical application of photocatalyts for the degradation of micropollutants in wastewater.

Activated Biomass-derived Graphene-based Carbons for Supercapacitors with High Energy and Power Density.

Here, we present a facile and low-cost method to produce hierarchically porous graphene-based carbons from a biomass source. Three-dimensional (3D) graphene-based carbons were produced through continuous sequential steps such as the formation and transformation of glucose-based polymers into 3D foam-like structures and their subsequent carbonization to form the corresponding macroporous carbons with thin graphene-based carbon walls of macropores and intersectional carbon skeletons. Physical and chemical activation was then performed on this carbon to create micro- and meso-pores, thereby producing hierarchically porous biomass-derived graphene-based carbons with a high Brunauer-Emmett-Teller specific surface area of 3,657 m2 g-1. Owing to its exceptionally high surface area, interconnected hierarchical pore networks, and a high degree of graphitization, this carbon exhibited a high specific capacitance of 175 F g-1 in ionic liquid electrolyte. A supercapacitor constructed with this carbon yielded a maximum energy density of 74 Wh kg-1 and a maximum power density of 408 kW kg-1, based on the total mass of electrodes, which is comparable to those of the state-of-the-art graphene-based carbons. This approach holds promise for the low-cost and readily scalable production of high performance electrode materials for supercapacitors.

The correlation of carotid artery stiffness with heart function in hypertensive patients.

BACKGROUND: The strength of each heart beat and the stiffness of large arteries contribute to blood pressure (BP). When the large arteries are stiff and their resistance greater, the afterload increases and this may change the function of the heart. However, the relation between common carotid artery stiffness and heart function in hypertensive patients has not been clarified. METHODS: Two hundred and twenty hypertensive patients underwent transthoracic and carotid echocardiography. Measurements of local arterial stiffness were taken at the right common carotid artery level and stiffness parameter (ß), pressure-strain elasticity modulus and intima-media thickness were calculated. Brachial cuff BP was measured just before starting the carotid study. The patients with any cardiovascular disease, diabetes mellitus, stroke, transient ischemic attack, or carotid stenosis were excluded. RESULTS: Carotid artery stiffness parameter (ß) was correlated with age and left ventricular mass index (p < 0.005). Even though ß was not correlated with LV systolic function, it was inversely correlated with diastolic function as measured by early mitral annular velocity. When the artery was stiffer, early mitral annular velocity (e') decreased (p < 0.001) and the index of left atrial (LA) pressure (early diastolic mitral inflow E velocity/e') increased (p = 0.001). In logistic regression, diastolic dysfunction was affected by age (beta -0.385, p = 0.001), LA volume index (beta 0.175, p = 0.013) and ß (beta -0.273, p = 0.019). CONCLUSION: In hypertensive patients, changes in carotid artery stiffness can affect the diastolic function, independent of age and LA volume index. Therefore, measurements and control of carotid stiffness can play an important role in the prevention of diastolic heart failure.