Showing papers in "Journal of Photochemistry and Photobiology A-chemistry in 2018"

Concurrent synthesis of nitrogen-doped carbon dots for cell imaging and ZnO@nitrogen-doped carbon sheets for photocatalytic degradation of methylene blue

Abstract: The hybrid composite of ZnO nanoparticles decorated nitrogen-doped graphitic carbon sheets (ZnO@N-C) alongside nitrogen-doped carbon dots (N-CDs) were synthesized by the direct hydrothermal method of peach fruit juice and ZnO nanoparticles (ZnO NPs). The synthesized ZnO@N-C hybrid composite and N-CDs were thoroughly characterized by various physicochemical techniques including powder X-ray diffraction (PXRD), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray (EDX) spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and fluorescence spectroscopy. The ZnO NPs were dispersed in the graphitic carbon structure with an average size of 25 ± 5 nm. The chemical composition of C, O, N, and Zn within the ZnO@N-C hybrid composite exhibits enough graphitization. Methylene blue (MB)-degradation was estimated utilizing the ZnO@N-C hybrid composite, a maximum degradation efficiency of >95% was achieved in a neutral aqueous medium within 60 min under UV-light irradiation. This maximum efficiency allows estimating the contribution of the heterogeneous and homogeneity of ZnO@N-C hybrid composite which is responsible for the MB-degradation. Moreover, the economic natural biosource or bio-waste was employed for the synthesis of ZnO@N-C hybrid composite and displays an excellent photocatalytic degradation under UV-light irradiation which is an alternate for other carbon-based metal oxides. In addition, the resulting N-CDs were utilized as a fluorescence probe for cellular imaging, owing to their tremendous properties such as bright fluorescence with high quantum yield, excellent water solubility, and good biocompatibility. The N-CDs displays a multicolour fluorescence based on their changing of excitation wavelength and these multicolour fluorescence emissions offered a multicolour cellular imaging which could be applicable for real biological system in the near future.

ZnO nanoparticles decorated multi-walled carbon nanotubes for enhanced photocatalytic and photoelectrochemical water splitting

Abstract: This paper describes the synthesis of ZnO/MWCNT nanocomposite, and their potential application in photoelectrochemical (PEC) water splitting for hydrogen generation and photocatalytic degradation of methylene blue dye. For the synthesis of nanocomposite, ZnO nanoparticles were grown on the MWCNT surface by a simple chemical route. Microscopic studies showed that ZnO nanoparticles were well dispersed on the MWCNT surface and Raman study confirmed the intimate integration between ZnO and MWCNT. The nanocomposite exhibit higher photocatalytic degradation of methylene blue dye as compared to bare ZnO. The ZnO/MWCNT photoanode shows ∼5 times increase in photocurrent density in comparison to pure ZnO, at an applied potential of +1 V vs. Ag/AgCl. The enhanced photocurrent density of ZnO/MWCNT photoanode is attributed to the decrease in band-bending and effective interfacial electron transfer due to the conducting CNT scaffold, which facilitates the charge collection and charge transport in the ZnO/MWCNT nanocomposite. The Electrochemical impedance spectroscopy measurements confirmed the faster charge transfer at the interface in the case of nanocomposite. These results suggest substantial potential of ZnO/MWCNT nanocomposite in dye degradation and PEC water splitting applications.

Facile synthesis of CdS/TiO2 nanocomposite and their catalytic activity for ofloxacin degradation under visible illumination

Abstract: In this paper, CdS/TiO2 nanoparticles were hydrothermally synthesized and characterized in detail to understand its crystalline, structural, morphological, thermal and optical properties using various spectroscopic and analytical techniques. The characterization results confirmed that the prepared nanoparticles exhibited high purity, crystallinity and excellent optical properties. The photocatalytic activity of as-synthesized CdS/TiO2 nanoparticles was evaluated for the degradation of ofloxacin under visible light irradiation. The CdS/TiO2 nanoparticles exhibited superior photocatalytic activity, and about 86% of ofloxacin was degraded in 180 min of visible illumination which was higher than bare TiO2. The enhanced photocatalytic activity of nanocomposite was attributed to the availability of more active sites for the drug molecules and effective response in visible region. Active species trapping experiments and photoluminescence terephthalic acid technique confirmed that hydroxyl radicals ( OH) are the prominent group for the photodegradation of fluoroquinolone drug, ofloxacin. Based on the scavenger study, photodegradation mechanism was proposed. Further, the CdS/TiO2 was used as a photocatalyst for simulated hospital wastewater and about 48.5% TOC reduction was observed with CdS/TiO2 (0.45 g/L) in 270 min under visible light.

Facile fabrication of novel ZnO/CoMoO4 nanocomposites: Highly efficient visible-light-responsive photocatalysts in degradations of different contaminants

Abstract: A facile route was adopted to fabricate p-n heterojunction ZnO/CoMoO4 photocatalysts through a refluxing method followed by calcination process. The resulting ZnO/CoMoO4 nanocomposites were characterized by means of XRD, EDX, FESEM, HRTEM, XPS, UV–vis DRS, FT-IR, BET, and PL techniques. The photocatalytic degradation of rhodamine B was chosen to investigate photocatalytic performances. Compared to the reference materials of ZnO and CoMoO4, the ZnO/CoMoO4 nanocomposites showed much higher photocatalytic activity and the ZnO/CoMoO4 (30%) sample possessed the highest efficiency, which is 19.6 and 6.26 folds greater relative to the ZnO and CoMoO4, respectively. The results demonstrated that the p-n heterojunction between ZnO and CoMoO4 could significantly boost the photocatalytic efficiency through highly promoted separation of electron/hole pairs as well as extended absorption to visible light. Finally, the highly enhanced performances of the ZnO/CoMoO4 (30%) nanocomposite in removal of three more organic pollutants including methylene blue, methyl orange, and fuchsine were confirmed, which indicates the potential of this nanocomposite for practical applications.

Silver nanoparticle loaded TiO2 nanotubes with high photocatalytic and antibacterial activity synthesized by photoreduction method

Abstract: Silver nanoparticles (Ag NPs) were loaded on TiO2 nanotubes (TNTs) via photoreduction method at room temperature without any additional reducing agent. The morphology and crystal structure were examined by transmission electron microscopy, X–ray diffraction pattern, and Raman spectroscopy. Chemical states of silver, titanium, and oxygen were analyzed by X–ray photoelectron spectroscopy. The results showed that Ag NPs with an average diameter of 5 nm were uniformly distributed on TNTs surface. Ag NPs improved both photocatalytic and the antibacterial activity of TNTs under sunlight irradiation. Ag/TNTs decomposed 81.2% of methylene blue and 75.8% of methylene orange after 150 min under sunlight irradiation. In addition, Ag/TNTs at 20 ppm concentration eliminated 99.99% of Staphylococcus aureus after 60 min under sunlight irradiation. This research demonstrated that Ag/TNTs can be synthesized at industrial scale by the photoreduction method and are effective antibacterial materials.

Engineering highly effective and stable nanocomposite photocatalyst based on NH2-MIL-125 encirclement with Ag3PO4 nanoparticles

Abstract: The development of highly efficient photocatalyst under visible light still a challenge. Herein we present band gap modification of NH2-MIL-125 by encirclement with suitable semiconductor that possesses a narrow band gap Ag3PO4 nanoparticles (NPs). The band gap of NH2-MIL-125 was decreased from 2.51 to 2.39 eV, making them potential candidates for photocatalytic applications. Our prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). TEM characterizations indicated that NH2-MIL-125 MOFs are coated with Ag3PO4 NPs. The photocatalytic activity (PCA) was evaluated in the liquid-solid phase, by monitoring the degradation of an organic dye (methylene blue (MB) and rhodamine-B (RhB)) under visible-light irradiation. Furthermore, the Ag3PO4@NH2-MIL-125 nanocomposites shown themselves to be the most active with the reaction rate being 39 and 35 times higher than the well known Degussa P25 TiO2 toward photocatalytic degradation of MB and RhB.

Mechanistic investigation of visible light responsive Ag/ZnO micro/nanoflowers for enhanced photocatalytic performance and antibacterial activity

Abstract: Visible light responsive Ag-doped flower-like ZnO (Ag/ZnO) micro/nanostructure photocatalysts with different loadings of Ag were successfully fabricated through surfactant-free co-precipitation and photodeposition routes. The as-prepared samples have been characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence spectroscopy (PL). The photocatalytic tests demonstrated that the Ag/ZnO micro/nanoflowers enhanced visible light responsive photoactivity towards the degradation of Fast Green dye and inactivation of Escherichia coli. Particularly, the 5 wt% Ag/ZnO samples showed excellent photoactivity in comparison with those of pure ZnO and commercial TiO2. The PL spectra showed that the Ag incorporation could effectively stimulate the separation efficiency of photogenerated charge carrier in Ag/ZnO. The trapping experiments indicated that superoxide anion ( O2−) radicals and hole (h+) were the major reactive oxygen species for the Ag/ZnO photocatalytic system. Much effort was also focused on the visible light photocatalytic antibacterial activity using Escherichia coli by observing the antibacterial response, minimum inhibitory concentration (MIC) and membrane integrity assay. The results showed that the Ag/ZnO can be used as photocatalysts and antibacterial agents for potential practical applications in the wastewater treatment.

Synthesis of mesoporous core-shell CdS@TiO 2 (0D and 1D) photocatalysts for solar-driven hydrogen fuel production

Abstract: The hydrogen production from photocatalytic water splitting has attracted extensive attention, as a direct way to convert solar energy into a chemical fuel. Herein, we report straightforward a simple method to synthesize a mesoporous core-shell CdS@TiO 2 (0D and 1D) photocatalysts with Pt NPs as a cocatalyst for H 2 fuel evolution under solar irradiation and presence of a sacrificial agent. The thickness of the TiO 2 shell is conveniently controlled from 10 to 30 nm by simply using sol-gel chemistry. Tiny Pt NPs about 0.1, 0.5 and 1 wt.% were photodeposited on CdS@TiO 2 nanocomposite during the photoreaction of hydrogen production. The effect of core-shell nanostructures on the photocatalytic activity was investigated, including the size, shape, and BET surface area of the CdS (0D and ID), and the thickness, surface area and porosity of the TiO 2 shell. The prepared CdS@TiO 2 /Pt photocatalysts absorb in the visible region of the solar spectrum and exhibit an excellent photocatalytic activity, compared with those reported in the literature. The 0D-CdS@TiO 2 /Pt photocatalysts achieve H 2 -evolution rate up to 4080 μmol during 6 h of sunlight irradiation. The mesoporous structure and large specific surface area of the prepared photocatalysts can accommodate more surface-active sites and facilitate the transport of charge carriers in visible light.

Facile fabrication of NiTiO3/graphene nanocomposites for photocatalytic hydrogen generation

Abstract: Nickel titanate on reduced graphene oxide (NiTiO3/rGO) were elaborated by facile microwave ignition method. The prepared nanomaterials were controlled using different ratios of GO to NiTiO3. The synthesized photocatalysts were characterized by X-Ray Diffraction (XRD), Raman Spectroscopy, Infrared Spectroscopy, Transmission Electron Microscopy (TEM), and UV-Reflectance Spectroscopy. The results demonstrate that photocatalytic performance of the photocatalysts for hydrogen generation increases up to 8383 μmol/(h.g) with increasing graphene content up to 5%). However, further increase in graphene content above this optimum level has decreased the performance of photocatalyst. The enhanced photocatalytic performance for hydrogen evolution is attributed to extension of its absorption edge to the visible light region, directly related to retard recombination of electron-hole pairs due to synergistic effects of NiTiO3 and graphene which leads to more efficient utilization of the solar energy.

Preparation, evaluations and operating conditions optimization of nano TiO2 over graphene based materials as the photocatalyst for degradation of phenol

Abstract: The preparation of the TiO2@graphene nanocomposites is significant due to its applications in the various industries such as sensor and catalytic purposes. In this study, the TiO2 and graphene-based nanocomposites have been synthesized via a simple one-step hydrothermal procedure by use of two precursors for graphene in water and ethanol as the solvents. Our fabricated photocatalysts are eco-friendly and can be recovered easily. Besides, a comparative study between graphene (GR) and graphene oxide (GO) as the graphene precursors for the photocatalytic degradation of phenol was performed. The obtained TiO2 and graphene-based nanocomposites were characterized by XRD, FESEM, EDX, FTIR, BET, NH3-TPD, PL, Raman, EDS and TGA techniques. In addition, the central composite design coupled with the response surface methodology by the Design Expert software was employed to design the experiments, optimization, and modeling of phenol decomposition. The influences of the process variables including the; solution pH, initial phenol concentration and photocatalyst amount on phenol degradation were investigated by the response surface method. In order to examine the provided model, an analysis of variance was performed for linear and quadratic equations for GO and GR-based photocatalysts in which satisfy the statistical criteria. The titanium-graphene nanocomposites has been demonstrated more photocatalytic performance than bare TiO2. It was found that a strong coupling between TiO2 nanoparticles and graphene sheets was formed. As compared with the pristine TiO2, the photocatalytic performance of the selected GO-based catalyst improved about 28% and GR-based photocatalyst increased about 15% for degradation of phenol. The empirical model and optimum conditions for the phenol degradation were obtained. Moreover, the as-synthesized photocatalysts can be recovered easily and reuse several times through the phenol degradation.

TiO2 nanoparticles and TiO2@graphene quantum dots nancomposites as effective visible/solar light photocatalysts

Abstract: In this paper, the photocatalytic activity of TiO2 NPs was improved twice: the first by engineering its morphology to narrow the band gap and to increase the surface area and the second by incorporating the modified TiO2 NPs with graphene quantum dots (GQDs) to reduce electron-hole ( e − h + ) recombination rate. Three visible/solar light responsive photocatalysts including TiO2 nanoparticles (NPs) and two nanocomposites of TiO2 @ GQDs were prepared. The photocatalytic activity of the prepared photocatalysts, GQDs, and P25 against Rhodamine B (RhB) under visible light or sunlight radiation was investigated. The prepared TiO2 NPs possessed very small particle size of 7.62 nm, large surface area of 236 m2 g−1, and narrow band gap of 2.41 eV. TiO2 NPs could harvest the visible/solar light for degrading RhB. The photocatalytic activity of TiO2 @ GQDs nanocomposites prepared by hydrothermal and ultrasound methods under visible light radiation are much better than that of TiO2 NPs. Using PL spectra, it was found that GQDs in the nanocomposites can hinder (or delay) e − h + recombination and hence improve the photocatlytic performance of TiO2 NPs. The photocatalytic degradation of RhB over TiO2 NPs and TiO2 @ GQDs nanocomposites prepared by hydrothermal and ultrasound methods under visible light radiation followed the pseudo-first-order kinetics with the rate coefficients of 0.126, 0.170, and 0.149 min−1, respectively.

Line defect Ce3+ induced Ag/CeO2/ZnO nanostructure for visible-light photocatalytic activity

Abstract: This article reports, synthesis and characterization of the ternary Ag/CeO2/ZnO nanostructure which was tested for visible light photocatalytic degradation of industrial textile effluent. The HR-TEM and XPS results confirms the presence of line dislocation linear defect induced oxygen vacancy in the ternary Ag/CeO2/ZnO nanostructure. The oxygen vacancy creates narrow band gap (2.66 eV) was confirmed by DRS. The ternary Ag/CeO2/ZnO nanostructure showed superior photocatalytic activity compared with pure ZnO, ZnO/Ag and ZnO/CeO2 results because of the narrow band gap, surface plasmon resonance (SPR) of Ag nanoparticles, synergistic effects, and defects (Ce3+ and oxygen vacancy) in CeO2 and ZnO.

Integration of carbon dots and polyaniline with TiO2 nanoparticles: Substantially enhanced photocatalytic activity to removal various pollutants under visible light

Abstract: In this study, ternary photocatalysts were fabricated through integration of carbon dots (CDs) and polyaniline (PANI) with TiO2 nanoparticles by a facile route. The photocatalysts were characterized by XRD, SEM, HRTEM, EDX, BET, XPS, FT-IR, UV–vis DRS, and PL instruments. Among the photocatalysts, the TiO2/CDs/PANI (20%) nanocomposite exhibited much higher photocatalytic performance for removal of RhB, MO, MB, and fuchsine in comparison with the TiO2, TiO2/CDs, and TiO2/PANI (20%) photocatalysts under visible light. The degradation rate constant of RhB by TiO2/CDs/PANI (20%) nanocomposite was 481 × 10−4 min−1, which is almost 36.5 and 2.6 times more than those of the TiO2 and TiO2/CDs photocatalysts, respectively. It was confirmed that O2− played predominant role in RhB degradation. Finally, the mechanism for enhanced photocatalytic activity was also discussed. The improved visible-light photocatalytic performance was related to substantial absorption of visible light, diminished recombination of the charge carriers, and enhanced specific surface area.

A comparative study on mesoporous and commercial TiO2 photocatalysts for photodegradation of organic pollutants

Abstract: The photocatalytic activity of the mesoporous TiO2 nanoparticles for the photooxidation of different pollutants molecules such as methylene blue dye (MB), methanol, imazapyr, and phenol were evaluated and compared to that of the commercial photocatalysts either Aeroxide TiO2 P-25 or Hombikat UV-100. The XRD and nitrogen isotherm results of mesoporous TiO2 confirmed that TiO2 nanocrystals with anatase phase were obtained and they possess large pore volume and high surface area of 0.29 cm3 g−1 and of 162 m2 g−1, respectively. The photocatalytic efficiency of mesoporous TiO2 is 100% for all employed pollutants molecules, however it reduced to 60–80% and 40–60% using Aeroxide TiO2 P-25 and Hombikat UV-100, respectively. The initial photodegradation rate of the pollutants molecules over mesoporous TiO2 is higher 2 and 3–6 times than that Aeroxide TiO2 P-25 and Hombikat UV-100, respectively. The enhancement of mesoporous TiO2 is explained by easy diffusion of pollutants molecules into TiO2 pores, minimize light scattering and excess •OH accumulated concentration into pores. The mesoporous TiO2 nanoparticles possesses the transport characteristics of pollutants molecules involved in the photocatalytic reaction and, thus, promote the comprehensive photocatalytic activity.

A visible light FeS/Fe2S3/zeolite photocatalyst towards photodegradation of ciprofloxacin

Abstract: FeS and Fe2S3 semiconductors were coupled and supported onto clinoptilolite nanoparticles (CN) via sulfidizing of Fe(II) and Fe(III) exchanged CN. The composite was characterized by X-ray diffraction (XRD), scanning electron microscope-energy dispersive x-ray (SEM-EDX), transmission electron microscopy (TEM) and diffuse reflectance spectroscopy (DRS) techniques. To study of the synergistic effects of supporting and coupling, the photocatalytic activities of FeS-CN, Fe2S3-CN and FeS-Fe2S3-CN catalysts were evaluated in the photodegradation of ciprofloxacin (CIP) aqueous solution. The ratio of FeS/Fe2S3 played an important role in the photocatalytic activity of the coupled systems, so the catalyst FF1 which ion exchanged in a solution containing 0.1 mol L−1 Fe(II) and 0.15 mol L−1 Fe(III) showed the best activity in the degradation of CIP. To study the interactions of the experimental variables on the photocatalytic activity of the FeS-Fe2S3-CN catalyst, experiments were designed using response surface methodology (RSM) approach. The best results were obtained in the run with the following conditions: pH 3.7, catalyst dose of 2.8 g L−1, 3.8 mg L−1 of CIP during 102 min irradiation of the suspension. The satisfactory correlation coefficient (R2 = 0.9480) for the second order polynomial model, confirmed that the predicted data by RSM well agree with the experimental results.

CeO2/TiO2 nanostructures enhance adsorption and photocatalytic degradation of organic compounds in aqueous suspension

Abstract: Mixed oxide interfaces are critical in the delivery of active components in photocatalytic processes. Cerium doped TiO2 photocatalysts were prepared using a hydrothermal route to manipulate the morphology of the photocatalyst and improve the interaction between CeO2 and TiO2 nanoparticles. These changes were compared with the photocatalytic activity and adsorption capacity of the solids. The photocatalysts were used to degrade polyvinylpyrrolidone (PVP) and methylene blue (MB) as test compounds. A low photodegradation rate of PVP (0.0001 min−1 and 0.0005 min−1 under visible and UV light, respectively) was observed using Ce-doped photocatalysts, with no adsorption. The high adsorption capacity of MB (34.46 mg g−1) proved that the local morphology of the nanostructured CeO2/TiO2 photocatalysts is more important than the amount of CeO2 in the sample, and the main role of the CeO2 on mixed photocatalysts is to improve thermal stability during the synthesis. XRD, XPS, BET surface area, UV–vis and TEM techniques confirmed this conclusion. The rate of degradation of MB by the Ce-doped photocatalyst decreased dramatically when using the singlet oxygen scavenger L-Histidine (0.0214 min−1 to 0.0001 min−1), indicating a photocatalysis sensitized by the dye, under visible and UV light.

Visible light photocatalytic activity of macro-mesoporous TiO2-CeO2 inverse opals

Abstract: Macro-mesoporous TiO2 inverse opal materials were synthesized and they were tested as photocatalysts under visible light irradiation. The influence of cerium oxide addition towards the Rhodamine B (RhB) photodegradation activity was evaluated. Structural, textural, spectral and surface properties of the TiO2-CeO2 inverse opal nanocomposites were studied by XRD, XPS, SEM, TEM, N2 adsorption-desorption, Diffuse Reflectance UV–vis and Photoluminescence spectroscopies. Compared to commercial TiO2 anatase, the macro-mesoporous TiO2 inverse opal exhibited six times higher kinetic rate constant in the RhB degradation under visible light irradiation. The good photocatalytic activity was related to the peculiar structure of this material, providing higher active surface area and enhancement of the mass transfer phenomena due to a very significant porosity. A positive effect of ceria addition was observed in terms of increased photocatalytic activity (73% of RhB degradation after 120 min of irradiation) when the amount of the CeO2 was low (up to 3% wt). Moreover the TiO2-3%CeO2 exhibited the lowest photoluminescence band intensity among all samples, indicating that the best efficiency in the charge carriers separation occurs in this catalyst. The presence of Ce3+ species was favoured for small amounts of cerium oxide, resulting in a positive effect on the photoactivity. The mutual interaction between Ti and Ce metal cations promotes an easier charge transfer on the surface, accelerating in particular the Ce4+/Ce3+ redox process that is beneficial for the oxidation reactions. On the contrary the use of high amounts of cerium oxide (>5% wt) led to a progressive agglomeration of CeO2, thus increasing the crystal size of TiO2-CeO2 particles (from 27 to 33 nm) and favouring the coverage of TiO2 active sites. This work reports the preparation and some photoactivity tests of some visible light responsive nanomaterials for an efficient solar energy utilization.

Combined use of spectrophotometer and smartphone for the optical detection of Fe3+ using a vitamin B6 cofactor conjugated pyrene derivative and its application in live cells imaging

Abstract: Synthetically easy, a new chemodosimeter-type chromogenic and fluorogenic chemosensor L was developed by condensing 1-aminopyrene with the vitamin B6 cofactor pyridoxal for the selective detection of Fe3+. Receptor L exhibits a rapid colorimetric response from yellow to colourless and a distinct fluorescence enhancement at 441 nm with Fe3+ due to the cleavage of imine linkage. The optical responses from L in the presence of Fe3+ ions are highly specific, interference-free, can be monitored by smartphone and also observed within the live HeLa cells.

Fabrication of the metal-free biochar-based graphitic carbon nitride for improved 2-Mercaptobenzothiazole degradation activity

Abstract: The present study describes a metal-free biochar-based photocatalyst of g-C3N4-C, in presence of an abundant fade magnolia as carbon precursor via facial in-situ together growth method. As a consequence, the g-C3N4-C shows a better degradation efficiency to 2-Mercaptobenzothiazole (90%) than pure g-C3N4 (49%) under the visible light. The improved photocatalytic performance of g-C3N4 is attributed to the biochar can significantly against the g-C3N4 reunion and stacking during high temperature treatment, because the biochar can act as the attachments that make the g-C3N4 flat and no accumulation, which will further increase the active sites. Additionally, photo-electrochemical measurements proved the separation efficiency of electron-holes of g-C3N4 is enhanced by introduced of biochar, due to its good electron transmission ability. Moreover, the ESR measurement and capture experiment further confirmed the active radicals on degradation of MBT are h+ and O2−. This work may provide a promising approach for wastewater treatment by waste utilization of solid biomass and increasing the photocatalytic performance of g-C3N4.

N, S co-doped carbon dots for temperature probe and the detection of tetracycline based on the inner filter effect

Abstract: Nitrogen and sulfur co-doped carbon dots (N, S co-doped CDs) were prepared from glutathione with a hydrothermal method and developed for temperature probe as well as fluorescent sensor of tetracycline. The as-prepared N, S co-doped CDs exhibited good optical properties, stability, water solubility and high fluorescence quantum yield(17.5%). The fluorescence intensity of the N, S co-doped CDs varied with temperature in the range of 10–70 °C. Moreover, based on the inner filter effect (IFE), the nanoparticle-based sensor displayed a wide linear range of 0.1–65 μM (R2 = 0.9916) and provided an exciting detection limit of 0.04 μM (signal-to-noise ratio of 3) for quantifying tetracycline. More strikingly, the N, S co-doped CDs sensing system could commendably resist the interference from potential foreign substances, and achieved satisfactory recoveries, which indicated the excellent selectivity and sufficient accuracy of the sensor for real milk samples analyses. As a simple and effective optical nanosensor, the proposed N, S co-doped CDs hold admirable promise to broaden the applications in food analysis and others fields.

Solvent and substituent effect on the photophysical properties of pyrazoline derivatives: A spectroscopic study

Abstract: Pyrazoline derivatives are among solvatochromic dyes and they are the most widely used in many fields such as sensors, labeling agent and optoelectronic devices. Therefore, synthesis of new pyrazoline derivatives and determination of their optical behavior in different solvents are a very important research area. In this study, the solvatochromic behaviors of seven new synthetic pyrazoline derivatives, (4-[3-(4-Hydroxyphenyl)-5-aryl-4,5-dihydro-pyrazol-1-yl]benzenesulfonamides, compound 1-7), were determined in different solvents. As a result of the measurements, a large red shifts in the fluorescence spectra of the compounds studied were observed for each compound, when the polarity of the solvent increased. Kamlet-Taft and Catalan parameters were used to describe the solvent-soluble interactions. The obtained results showed that the solvatochromic behavior of the compounds is dependent on their solvent polarity as well as the effect of the hydrogen-bonding properties of the solvents. It was also found that the increases in the polarity of the solvent was facilitated the non-radiative transition. Furthermore, the changes in the dipole moments of compounds 1-7 in different solvents at room temperature were calculated by using the Lippert–Mataga equation. It was very impressive that calculated fluorescence quantum yield values of the compounds studied here by using different solvents were remarkably high than the ones reported in the literatures for pyrazolines. In addition, the effect of substituent on the photo-physical properties of the compounds was also investigated. It was observed that the fluorescence intensity of the substituted compounds 2-6 increased comparing to the compound 1, which is a non-substituted derivative. These changes were not dependent on electronic nature of the substituent on phenyl ring (i.e. electron donating and electron withdrawing substituent). According to data obtained it can be stated that these novel solvatochromic dyes studied here can be find application in pharmaceutical industry, as labeling agent, sensor applications as biosensors or analytical sensors and/or optoelectronic devices.

Inactivation of Staphylococcus aureus in visible light by morphology tuned α-NiMoO4

Abstract: α-NiMoO4 has been successfully implemented in different morphologies via microwave hydrothermal technique in presence of surfactants (Polyethylene Glycol, Sodium Citrate, and Sodium Dodecyl Sulfate) The inactivation of multidrug-resistant pathogens, Staphylococcus aureus (S aureus) has been investigated in the presence of visible light as well as in dark S aureus was inactivated in 6 h under visible light irradiation A slight inactivation of S aureus was observed in dark The generation of intracellular reactive oxygen species, ROS (O2 −, OH , and H2O2) in visible light was observed by using 2, 7-dichloro-dihydro-fluorescein diacetate (DCFA-DA) and nitro blue tetrazolium (NBT), which suggests the bacterial inactivation by ROS Nanowires morphology of α-NiMoO4 exhibited effective bactericidal efficiency in visible light as compared to small bundle of needles, nanorod, large bundle of needles because of small size/diameter, toxicity, enhancement of ROS generation, and high BET surface area The damages in the phospholipid layer present in the cell membrane of S aureus were observed by FESEM analysis Furthermore, the observation of DNA damages and protein degradation percentage give the evidence of ROS effect for deactivating the bacteria So, this study offers new insight into the photocatalytic inactivation of multidrug-resistant microorganisms by morphology modulated visible light driven α-NiMoO4 photocatalyst

Boron doped graphene oxide with enhanced photocatalytic activity for organic pollutants

Abstract: In present study, boron doped reduced graphene oxide (BR-GO) is synthesized by reducing graphene oxide (GO) in the presence of boric acid, and employed as a photocatalyst for the degradation of organic pollutants methyl orange (MO) and methylene blue (MB). GO and BR-GO are systematically characterized by X-ray diffraction, Raman spectroscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis spectroscopy. The modifications in the structure of GO are confirmed. The BR-GO has sheet structure with various graphene islands and disordered regions. The electrical conductivity has been measured using two-probe method. The conductance is explained by two-dimensional variable range hopping model. The photocatalytic activity of GO is enhanced on doping with boron due to increase in the density of states value near Fermi level. The adsorption mechanism and kinetic studies for the degradation of MB and MO dyes suggest that the photocatalytic degradation follows a pseudo-second order mechanism.

Feasibility of using combined TiO2 photocatalysis and RBC process for the treatment of real pharmaceutical wastewater

Abstract: The present study deals with the treatment of real pharmaceutical wastewater using photocatalysis followed by biological process. Actually feasibility studies in terms of Biodegradability Index (B.I.) were undertaken to see the efficacy of biological treatment, subsequent to photocatalytic treatment. The B.I. of the studied effluent came out to be 0.178 which was subsequently raised to 0.510 using photocatalysis as a primary treatment. Optimization for the photocatalytic process was conducted using BBD. The optimum values of parameters were found to be TiO2 dose = 0.6 g/L, pH = 3.20, t = 455 min. Experimentally% degradation at optimum conditions was found to be 63.7% which was very close to the suggested value of 67.02%.Analysis by GC–MS suggested the formation of short chained compounds after the photocatalytic treatment. Toxicity assay and B.I. confirmed the non toxicity and biodegradability of wastewater after photocatalytic treatment, respectively. The experimental data showed a reasonably good expression of second order kinetics. Biological treatment was followed by using Rotating Biological Contractor (RBC) for further degrading the COD, BOD to the limits according to standards suggested by concerned authorities. Overall% degradation efficiency of combined photocatalysis and biological process was 96.5% of which 67% corresponded to the photocatalysis and remaining 30% to the biological RBC.

Visible-light-driven photocatalytic degradation of pollutants over Cu-doped NH2-MIL-125(Ti)

Abstract: In our study, we carried out the first synthesis of new copper-doped titanium-based amine-functionalized metal-organic frameworks (Cu-NH2-MIL-125(Ti)) via an in situ doping method. The as-acquired materials were well distinguished by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP) emission spectroscopy, N2 adsorption-desorption measurements, UV–vis diffuse reflectance spectroscopy, photoluminescence (PL) spectroscopy, and photoelectrochemical experiments. The Cu-doped NH2-MIL-125(Ti) exhibited a significant improvement in photocatalytic activity compared to undoped NH2-MIL-125(Ti). When Cu was 1.5 wt%, the Cu-doped NH2-MIL-125(Ti) exhibited the greatest photocatalytic activity. The rate constants of the 1.5 wt% Cu-NH2-MIL-125(Ti) to degrade methyl orange (MO) and phenol were determined as 10.4 and 3.4 times as great as those of undoped NH2-MIL-125(Ti), respectively. The improved photocatalytic activity of Cu-NH2-MIL-125(Ti) could be ascribed to the elevated light absorption ability and additional effective charge transportations and separations. Further, the Cu-NH2-MIL-125(Ti) photocatalysts stayed steady following four consecutive cycles. Additional research proved that the holes and hydroxyl radicals were the primary active species in the degradation procedure.

UV-LED radiation modeling and its applications in UV dose determination for water treatment

Abstract: With the growing application of the ultraviolet light emitting diodes (UV-LED) for water treatment purposes, the significance of modeling their output for designing UV reactors becomes crucial. In this study, the radiation distributions of two UV-LEDs with different radiation profiles are modeled. These UV-LEDs represent the two most common radiation profiles of UV-LEDs – balloon shape and heart shape. Irradiance and fluence rate distribution were predicted and experimentally validated by measuring irradiance through an accurate radiometry setup and determining fluence rate by iodide-iodate actinometry. The consistency of the results among the actinometry, radiometry, and the model proves the reliability of the model. The model helps demonstrate the extend to which the irradiance distribution and average fluence rate are affected as a function of distance and how they are affected by the UV-LED’s radiation profile. For UV-LEDs with any radiation profiles, higher average fluence rate occurs at closer distances to the UV-LED; however, to study the microbiological inactivation kinetics, uniformity of the radiation distribution on the surface of the petri dish has to be taken into account. Using the validated model, common radiation modeling presumptions such as the point source assumption and symmetry assumption for radiation profile of UV-LEDs are evaluated.

Pt/TiO2 photocatalysts deposited on commercial support for photocatalytic reduction of CO2

Abstract: Pt/TiO2 (PC500) photocatalysts with different amount of Pt (0.5–3.0 wt.%) deposited on commercial support (Al2O3 foam) were characterized in detail by X-ray powder diffraction, nitrogen physisorption measurement, UV–vis diffuse reflectance spectroscopy, inductively coupled plasma optical emission spectrometry (ICP-OES), photoelectrochemical measurements and tested for CO2 photocatalytic reduction and compared with commercial anatase TiO2 PC500. The main reaction product was methane; however, hydrogen and carbon monoxide were also detected. The highest yields of CH4, H2 and CO were achieved in the presence of 1.5 wt.% Pt/TiO2. Base on the performed experiments, it was suggested that the key role in the CO2 photocatalytic reduction plays the potentials of electrons and holes within the electronic structure of photocatalyst, which were markedly affected by the Pt loading in such a way that it improved the transformation efficiency of CO2 to methane. Significantly higher yields of CO2 photocatalytic reduction were achieved in the presence of photocatalysts deposited on the commercial support compared to the powder photocatalysts. These findings confirmed the great importance of the supports surface areas on photocatalyst activity in photocatalytic reaction.

Determination of the crystallinity of TiO2 photocatalysts

Abstract: This study reports a new simple method to determine the crystallinity of anatase and rutile TiO2 photocatalysts. The crystallinity degree of various anatase and rutile samples was estimated by XRD analysis from the ratio among the full width at half maximum intensities of the main diffraction peaks of anatase or rutile and the (111) peak of CaF2 as internal standard. The photocatalytic activity of selected powders was tested employing the photodegradation of 4-nitrophenol in aqueous solution as probe reaction. The results showed that the photoactivity of the investigated samples increased with increasing crystallinity and crystallite size.

Visible-light photocatalytic activity of zinc ferrites

Abstract: Zinc ferrite samples were prepared at temperatures between 75 °C and 1100 °C employing published synthetic methods Phase pure zinc ferrites were, however, only obtained through high-temperature methods (more than 800 °C) as revealed by XRD and Raman analysis. Photocatalytic experiments under UV and visible light irradiation as well as a series of detailed wavelength dependent measurements applying monochromatic light sources emitting at wavelengths of 365, 455, 505, and 660 nm were performed. Visible light-induced bleaching of methylene blue in aqueous suspensions of zinc ferrites was observed. However, no photocatalytic formation of OH radicals was detected. The results of flat band potential measurements revealed the interfacial electron transfer from an excited methylene blue molecule into the conduction band of zinc ferrite to be thermodynamically possible. The bleaching of methylene blue containing suspensions under visible light irradiation is, therefore, assumed to be initiated by an interfacial electron transfer from photo-excited methylene blue molecules adsorbed on the ferrite surface into the conduction band of the semiconducting zinc ferrite.

Photocatalytic oxidation of six pesticides listed as endocrine disruptor chemicals from wastewater using two different TiO2 samples at pilot plant scale under sunlight irradiation

Abstract: The photocatalyzed degradation of a mixture of six pesticides (malathion, fenotrothion, quinalphos, vinclozoline, dimethoate and fenarimol) with endocrine disrupting activity has been studied in sewage wastewater effluent under natural sunlight at pilot plant scale. The initial level of each pesticide was 0.30 mg L−1. For this, two commercial TiO2 nanopowders (Degussa P25 and Kronos vlp 7000) were used as photocatalysts. The operational conditions (catalyst loading, effect of electron acceptor and pH) were previously optimized under laboratory conditions using a photoreactor. The results show that the use of TiO2 alongside an electron acceptor like Na2S2O8 strongly enhances the degradation rate of the studied pesticides compared with photolytic tests, especially Degussa P25. The photodegradation process followed pseudo-first order kinetics in all cases. In our experimental conditions, the necessary time necessary for 90% degradation (DT90) varied from 79 to 1270 min (6–108 min as normalized illumination time, t30W) for malathion and fenarimol, respectively for TiO2 vlp 7000 and 32–817 min (t30W = 3–69 min) for the same pesticides, in the case of TiO2 P25. The results confirm the efficacy of the treatment to remove recalcitrant pollutants from wastewater using natural sunlight as renewable source.