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A new strategy regarding the fabrication of chitosan (CS) or ethylene diamine tetraacetic acid (EDTA) on graphene oxide (GO) was performed. The nematocidal potential against Meloidogyne incognita causing root-knot infection in eggplant was tested. The plant immune response was investigated through measuring the photosynthetic pigments, phenols and proline contents, oxidative stress, and antioxidant enzymes activity. Results indicating that, the treatment by pure GO recorded the most mortality percentages of M. incognita 2nd juveniles followed by GO-CS then GO-EDTA. In vivo greenhouse experiments reveals that, the most potent treatment in reducing nematodes was GO-CS which recorded 85.42%, 75.3%, 55.5%, 87.81%, and 81.32% in numbers of 2nd juveniles, galls, females, egg masses and the developmental stage, respectively. The highest chlorophyll a (104%), chlorophyll b (46%), total phenols (137.5%), and free proline (145.2%) were recorded in GO-CS. The highest malondialdehyde (MDA) value was achieved by GO-EDTA (7.22%), and hydrogen peroxide (H2O2) content by 47.51% after the treatment with pure GO. Treatment with GO-CS increased the activities of catalase (CAT) by 98.3%, peroxidase (POD) by 97.52%, polyphenol oxidase (PPO) by 113.8%, and superoxide dismutase (SOD) by 42.43%. The synthesized nanocomposites increases not only the nematocidal activity but also the plant systematic immune response.

To obtain the synergistic antimicrobial potential of nano-composites conjugated with graphene oxide (GO), an alternative approach was developed throughout the hybridization of chitosan (CS) or ethylene diamine tetraacetic acid (EDTA) with GO. The synthesized GO-nanocomposites were identified by XRD, HRTEM, SEM, FTIR, Zeta potential, and Raman spectroscopy. The antimicrobial activity of GO, GO-CS, and GO-EDTA was investigated against some pathogenic bacteria and Candida sp. Results showed that nano-composites looked flattened and clear, with some lines and folds on the exterior part. SEM images show the basic morphology of GO which owns remarkable holes, crevasses, and indeclinable internal structure. GO-EDTA and GO-CS possess a promising antimicrobial activity against all pathogenic microbes. In-vitro ZOI result verified that they exhibited activity against Escherichia coli (22.0 mm for GO-EDTA and 11.0 mm for GO-CS), Staphylococcus aureus (15.0 mm for GO-EDTA and 10.0 mm for GO-CS) and Candida albicans (22.0 mm for GO-EDTA and 16.0 mm for GO-CS). Microbial cells may be ultimately-damaged when they interact with GO-based nanocomposites due to different mechanisms such as oxidative and membrane stress and wrapping isolation. This work provides revolutionary GO-nanocomposites for increasing the antimicrobial activity against some pathogenic microbes with a cost-effective and eco-friendly approach.

Photoelectrochemical (PEC) water splitting has emerged as a promising technology for the storage of renewable energy sources, via the production of hydrogen, a clean and multi-purpose chemical energy vector. The key component in a PEC cell is the photoanode where light energy is absorbed and transformed into electron-hole pairs of appropriate energy for water photo-oxidation. We report on the synthesis of g-C3N4 materials, with an elongated nano-structure, fabricated by the direct pyrolysis of supramolecular melamine used as a chemical precursor. The as-prepared material was used to host specific amounts of bismuth, a doping element used to adjust the band gap of the hosting matrix. The presence of Bi in the photoanodes was confirmed by energy dispersive x-ray analysis (EDX) analysis. Powder X-ray (p-XRD) and Fourier transform infrared (FT-IR) measurements performed on the photoanodes confirmed the absence of Bi-based oxides, and showed that bismuth may bonded to nitrogen atoms inside the voids of the g-C3N4 skeleton. Differential reflective spectroscopy (DRS) measurements revealed that the band gap energy was reduced upon introduction of Bi into g-C3N4. From photoluminescence (PL) plots, it was observed that the 2.5% Bi doping induced a 6-fold electron-hole separation, compared to the pristine g-C3N4. PEC water splitting measurements showed that 2.5% Bi doping approximately doubled the activity of g-C3N4 towards water oxidation. Electrochemical impedance spectroscopy (EIS) measurements showed that Bi doping was an effective method for decreasing the charge transfer across the electrode/electrolyte interface; 2.5% Bi-g-C3N4 was reduced by around 2.4 times compared to that of pristine g-C3N4. Bode-phase plots accompanied EIS spectra revealed that the lifetime of the photo-generated electrons in neat g-C3N4 was improved as a result of Bi doping. The band gaps and the positions of the valence and conduction bands were determined from Mott–Schottky plots.

Electrooxidation of urea is an efficient methodology for the production of hydrogen with a simultaneous treatment of urea-containing wastewaters. In this study, tungsten was suggested as a co-catalyst to foster the activity of Ni/C nanostructures in the process of urea electro-oxidation. Beside optimization of the co-catalyst content, influences of the nano-morphology and the synthesis temperature have been investigated. The results indicated that WNi nanoparticles-incorporated carbon nanofibers can be produced from calcination of electrospun mats composed of nickel acetate, tungsten chloride, and ploy (vinyl alcohol). Compared to the nanoparticles, the morphology of nanofibrous was strongly foster the electrocatalytic activity. The W-free and the prepared, from calcination of an electrospun solution containing 10 wt% WCl2 at 850 °C, nanofibers give better performance compared to the nanoparticles having similar compositions. Compared to the nanoparticles, the nanofibrous morphology results in increasing the current density from 11.5 to 16 mA/cm2 (28% increase) and from 22 to 37.75 mA/cm2 (42% increase) for the pristine and W- containing catalyst, respectively. Studying the influence of the metallic nanoparticles composition indicated that the tungsten content strongly affects the electrocatalytic activity; the nanofibers prepared from electrospun solution containing 35 wt% tungsten precursor reveal the best performance. Investigating the effect of the calcination temperature indicated that 1000 °C is the optimum temperature compared to 700 and 850 °C. Numerically, for 10 wt% co-catalyst sample, the current density was duplicated four times when the calcination temperature increased from 850 to 1000 °C. Studying the kinetic of urea oxidation reaction concluded that the activation energy is ~17 kJ/mol.

The development of new sources of renewable energy fuels like hydrogen remains challenging considering the nowadays society energy needs on a day-to-day basis. In this context, hybrid nanostructures conformed by TiO2 nanoparticles sensitized with bundles of rod-like Sb2S3 (stibnite) on the surface of reduced graphene oxide (TiO2/Sb2S3/RGO), can pave the way in this direction, as offering heterostructures that can be employed as the active phase in photo-anodes for photoelectrochemical water oxidation. For that, these TiO2/Sb2S3/RGO heterostructures are able to extend the light absorption to the visible range, enhance the charge separation and transportation, and improve the conductivity of the catalyst. Furthermore, the method of synthesis, though simple, implies a one-pot strategy by which the TiO2 nanoparticles and the Sb2S3 rod-like particles are independently produced at the surface of RGO sheets, warranties the proper improved function of the hybrids and offers the engineering of future chalcogenide-based catalysts with promising water splitting photoelectrochemical properties. Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG Agencia Estatal de Investigación | Ref. CTM2017-84050-R Agencia Estatal de Investigación | Ref. PID2020-113704RB-I00 Xunta de Galicia | Ref. IN607A 2018/5 Xunta de Galicia | Ref. ED431G 2019/06

A composite of tubular g-C3N4 with α-Fe2O3 has been synthesized to improve the photocatalytic performance of tubular g-C3N4 by the formation of a Z-scheme heterostructure. The composites were fabricated by the combination of varying amounts of hydrothermally synthesized α-Fe2O3 nanotubes (NTs) and protonated ruptured tubular (RT) g-C3N4, by the electrostatic self-assembly method. The obtained composites were characterized by zeta potential, powdered-X-ray diffraction (p-XRD), scanning/transmission electron microscopy (S/TEM), photoluminescence (PL), and Fourier transform infrared spectroscopy (FTIR). PL and photocurrent measurements indicates a higher charge separation of the photo-generated electron-hole pair for Fe2O3 NTs/RT g-C3N4 composite with higher concentration of α-Fe2O3 NTs. UV–Vis diffuse reflectance spectroscopy (UV–Vis/DRS) shows the band gaps of pristine α-Fe2O3 NTs and RT g-C3N4 to be 1.86 eV and 2.72 eV respectively, while the band structures were determined by Mott-Schottky measurements. I-V curves obtained from photoelectrochemical water splitting shows that the formation of the composite decreased the oxidation overpotential as compared to pristine α-Fe2O3 NTs and pristine RT g-C3N4. Bode plots showed that the composite was able to increase the lifetime of the photo-generated electrons as compared to both RT g-C3N4 and α-Fe2O3 NTs.

Nowadays, development of highly efficient potentiometric sensors attracts the attention of many researchers over the world; due to the great expansion of portable analytical devices. This study aims to apply a current development to the construction and sense of carbon paste sensors based on flowered-like Mg-Al layered double hydroxides/multiwalled carbon nanotubes (FLLDH/MWCNTs) (sensor І), FLLDH/titanate nanotubes (TNTs) (sensor ІІ) and MWCNTs/TNTs (sensor ІІІ) nanocomposites for bambuterol hydrochloride analysis; to enhance the potentiometric response towards determination of the drug. The sensors exhibited excellent Nernstian slopes 58.8 ± 0.5, 58.5 ± 0.8 and 57.4 ± 0.7 mV/decade with linear working ranges of 1.0 × 10−7–1.0 × 10−2, 1.0 × 10−6–1.0 × 10−2 and 1.0 × 10−7–1.0 × 10−2 mol L−1, detection limits 2.3 × 10−8, 2.5 × 10−7and 7.5 × 10−8 mol L−1 and quantification limits of 7.6 × 10−8, 8.3 × 10−7and 2.5 × 10−7 mol L−1 for sensor І, ІІ and ІІІ, respectively. The selectivity behaviour of the investigated sensors was tested against biologically important blood electrolytes (Na+, K+, Mg2+, Ca2+). The proposed analytical method was successfully applied for BAM determination in pure drug, pharmaceutical products, surface water, human plasma and urine samples with excellent recovery data (99.62, 99.10 and 98.95%) for the three sensors, respectively.

A series of nanosized CeO2–Fe2O3 mixed-oxide nanocomposites with different Ce4+/Fe3+ molar ratios were successfully prepared by a co-precipitation technique. The surface area increased with Fe2O3 content increasing up to 60 wt% in the composite. However, with further increase in Fe2O3 content, the surface area began to decrease. The reduction processes of the CeO2–Fe2O3 nanocomposites were studied in a hydrogen atmosphere at 300–600 °C. The reduction rates increased by increasing both the temperature and Fe2O3 content in the nanocomposites. The microstructure of the reduced composites at 500 °C illustrated the presence of a considerable number of macro- and micro-pores. The activation energy values were calculated which were in the range of 3.56–5.37 kJ·mol−1 at the initial stages (up to 35% reduction) and 5.21–10.2 kJ·mol−1 at the final stages (up to 80% reduction) of reduction. The rate-controlling mechanisms in both the initial and final reduction stages were determined, and the initial reaction stage was controlled by combined gaseous diffusion and interfacial chemical reaction mechanisms for all the composites except for pure CeO2, which was controlled by a chemical reaction mechanism. The final reaction stage was controlled by a gaseous diffusion mechanism for some composites, while for the others it was controlled by combined gaseous diffusion and interfacial chemical reaction mechanisms. The hydrogen sorption properties of the nanocomposites were studied by pressure composition isotherms using a volumetric method. Hydrogen storage in the nanocomposites increased by increasing the temperature because of the formation of oxygen vacancies which enhance atomic H adsorption and function as strong adsorption sites forming more metal hydride covalent bonds.

Photoelectrochemical water splitting can be regarded as a promising technology for renewable hydrogen production. In the current work, a facile hydrothermal synthesis method was used to directly grow TiO2 flower-like structures/TiO2 nanorods on a conductive glass substrate. Moreover, three different gold deposition methods, namely, a photoreduction method (PR), the Turkevich method (TK) and a combination of both methods (CM), were applied to decorate the formed flower-like structures with gold nanoparticles (GNPs). The type of deposition technique affected the size, size distribution, loading, surface coverage and shape of the obtained GNPs. With the PR technique, the photocurrent increased 3.5-fold compared to that of the bare flower-like structures. With the TK method, a narrow GNP distribution was obtained, yielding a 6.15-fold increase in photocurrent. Using the CM approach, a 1.21-, 26.86- and 12.79-fold increase was observed for current density compared to that of the corresponding bare samples. All samples showed stable chronoamperometric performance under illumination without any signs of photocorrosion or performance deterioration. Electrochemical impedance spectroscopy showed that the CM approach decreased the semiconductor/electrolyte interfacial resistance to 37, 2.5 and 3.1% of the values for the bare samples. Bode phase plots showed that the stacked flower-like structures can be considered electron-hole recombination centres, leading to an observable broadening of the maximum-frequency peak.

The preparation of magnetic nanotubes opens new avenues in nanobiotechnology as a consequence of their multiple properties embedded within the same moiety. Here, we report on synthesis and characterization of titanate nanotubes and their Fe-/Co-doped by means of X-ray diffraction, high-resolution transmission electron microscopy, and magnetic studies. Although the absence of 3d elements in Na2Ti3O7 nanotubes, our data for the first time, exhibits room temperature M−H hysteresis. Furthermore, our results show that the magnetization increased with Fe doping, while Co doping enhanced the coercivity. This behaviour was expected from the magnetic character of Fe and the positive magnetocrystalline anisotropy of Co. These results give access to the doping effect on tuning the properties of Na2Ti3O7 nanotubes.

In this work, efficient methanol oxidation fuel cell catalysts with excellent stability in alkaline media have been synthesized by including transition metals to the layered double hydroxide (LDH) nanohybrids. The nanohybrids CoCr-LDH, NiCoCr-LDH and NiCr-LDH were prepared by co-precipitation and their physicochemical characteristics were investigated using TEM, XRD, IR and BET analyses. The nanohybrid CoCr-LDH is found to have the highest surface area of 179.87 m2 g−1. The electrocatalytic activity measurements showed that the current density was increased by increasing the methanol concentration (from 0.1 to 3 M) as a result of its increased oxidation at the surface. The nanohybrid NiCr-LDH, showing the highest pore size (55.5 A) showed the highest performance for methanol oxidation, with a current density of 7.02 mA cm−2 at 60 mV s−1 using 3 M methanol. In addition, the corresponding onset potential was 0.35 V (at 60 mV s−1 using 3 M methanol) which is the lowest value among all other used LDH nanohybrids. Overall, we observed the following reactivity order: NiCr-LDH > NiCoCr-LDH > CoCr-LDH, as derived from the impedance spectroscopy analysis.

In the last decade, nanosized metal organic frameworks (NMOFs) have gained an increasing applicability as multifunctional nanocarriers for drug delivery in cancer therapy. However, only a limited number of platforms have been reported that can serve as an effective targeted drug delivery system (DDSs). Herein, we report rational design and construction of doxorubicin (DOX)-loaded nanoscale Zr (IV)-based NMOF (NH2-UiO-66) decorated with active tumor targeting moieties; folic acid (FA), lactobionic acid (LA), glycyrrhetinic acid (GA), and dual ligands of LA and GA, as efficient multifunctional DDSs for hepatocellular carcinoma (HCC) therapy. The success of modification was exhaustively validated by various structural, thermal and microscopic techniques. Biocompatibility studies indicated the safety of pristine NH2-UiO-66 against HSF cells whereas DOX-loaded dual-ligated NMOF was found to possess superior cytotoxicity against HepG2 cells which was further confirmed by flow cytometry. Moreover, fluorescence microscopy was used for monitoring cellular uptake in comparison to the non-ligated and mono-ligated NMOF. Additionally, the newly developed dual-ligated NMOF depicted a pH-responsiveness towards the DOX release. These findings open new avenues in designing various NMOF-based DDSs that actively target hepatic cancer to achieve precise therapy.

International audience; Fast and efficient identification of bacterial pathogens in water and biological fluids is an important issue in medical, food safety, and public health concerns that requires low-cost and efficient sensing strategies. Impedimetric sensors are promising tools for monitoring bacteria detection because of their reliability and ease-of-use. We herein report a study on new biointerface-based amphiphilic poly(3-hexylthiophene)-b-poly(3-triethylene-glycol-thiophene), P3HT-b-P3TEGT, for label-free impedimetric detection of Escherichia coli (E. coli). This biointerface is fabricated by the self-assembly of P3HT-b-P3TEGT into core–shell nanoparticles, which was further decorated with mannose, leading to an easy-to-use solution-processable nanoparticle material for biosensing. The hydrophilic block P3TEGT promotes antifouling and prevents nonspecific interactions, while improving the ionic and electronic transport properties, thus enhancing the electrochemical-sensing capability in aqueous solution. Self-assembly and micelle formation of P3HT-b-P3TEGT were analyzed by 2D-NMR, Fourier transform infrared, dynamic light scattering, contact angle, and microscopy characterizations. Detection of E. coli was characterized and evaluated using electrochemical impedance spectroscopy and optical and scanning electron microscopy techniques. The sensing layer based on the mannose-functionalized P3HT-b-P3TEGT nanoparticles demonstrates targeting ability toward E. coli pili protein with a detection range from 103 to 107 cfu/mL, and its selectivity was studied with Gram(+) bacteria. Application to real samples was performed by detection of bacteria in tap and the Nile water. The approach developed here shows that water/alcohol-processable-functionalized conjugated polymer nanoparticles are suitable for use as electrode materials, which have potential application in fabrication of a low-cost, label-free impedimetric biosensor for the detection of bacteria in water.

International audience; AbstractMainconclusion WeobservedaclosecorrelationbetweentheinhibitionofphotosystemIIandtheoxidationofpoly- phenols during an acute oxidative stress in sunflower leaf discs.Abstract To assess the physiological significance of polyphenols as antioxidants in planta, we compared the kinetics of polyphenols oxidation with the inhibition of the photosynthetic apparatus in sunflower leaf discs exposed to an acute pho- tooxidative stress. Illumination of leaf discs in the presence of methyl viologen induced a rapid and large non-photochemical quenching of chlorophyll-a fluorescence, which was reversed after 4 h of treatment as indicated by the ≈ 30% increases of the steady-state (Fs) and maximal (Fm′) levels of chlorophyll-a fluorescence relative to the first hour of treatment. This event coincided with the accelerated decreases of the maximum (Fv/Fm) and effective (∆F/Fm′) quantum yields of photosystem II, and also with the beginning of polyphenols oxidation, estimated by the UV absorbance of methanolic leaf extracts, and supported by the Folin–Ciocalteu method and cyclic voltammetry. The decreases of Fv/Fm and the concentrations of reduc- ing polyphenols were highly correlated (R2 = 0.877) during the experiment. Coherent with the decrease of UV absorbance of methanolic extracts, polyphenol oxidation resulted in a marked decrease of UV absorbance of leaf epidermis. Also, polymerization of oxidized polyphenols caused the accumulation of brown pigments in the MV-treated leaf discs, decreas- ing leaf reflectance, especially at 550 and 740 nm. Fluorescence intensities were also decreased during the MV treatment. Interestingly, the emission fluorescence ratio F740/F684 (excitation at 550 nm) decreased similarly to Fv/Fm (R2 = 0.981) due to the brown pigments. Moreover, the excitation fluorescence ratio F484/F680 (emission at 740 nm) was linearly correlated (R2 = 0.957) to ∆F/Fm′, indicating a decrease of efficiency of energy transfer between the antenna pigments to the photosystem II reaction center during the oxidative stress. These results support the view that polyphenols can be effective antioxidants protecting the plants against reactive oxygen species.

A main challenge hindering the development of efficient solar fuel cell systems is the identification of robust, cost-effective, and abundant catalysts. Herein, we demonstrate the ability to synthesize photoactive, relatively cheap and abundant catalyst for the solar-assisted water splitting. The proposed catalyst is a composite of Co Cu/graphene immobilized on hierarchical hollow mesoporous Titania. Diffuse Reflectance analysis showed visible light absorption for (Co Cu) 2% TiO2/RGO with an estimated band gap of 2.41 eV, as compared to 3.13 eV for Titania. Photoluminescence spectra showed a significant decreasing in recombination rate of photogenerated electron-hole pair for (Co Cu) 2% TiO2/RGO nanocomposites. Upon their use as photoanodes in solar fuel cells, the fabricated nanocomposites show 14-fold increase in photocurrent density compared to Titania. This enhancement was confirmed via the measurement of electron and phonon life times. The results attained in this study demonstrate a step toward using non-precious co-catalysts to boost the performance of photocatalysts in solar fuel cells.

Ni-Al-CO3-layered double hydroxide (LDH) with Ni:Al ratio (3:1) and their nanocomposites with alginate and chitosan beads were prepared and examined for their efficiency in removal of Cd2+ and Cu2+ ions from wastewater. Different parameters such as contact time, pH value, adsorbent weight, and heavy metal ion concentration on the removal efficiency were examined and reported. The prepared beads were examined using X-ray diffraction (XRD), TEM, SEM, and FTIR. Our results revealed a successful preparation of the LDH in rhombohedral hexognal crystal form and the alginate-LDH-chitosan beads. The optimized batch experiment conditions in ambient room temperature were found to be 2 g/L adsorbent dose, 50 mg/L initial concentration of meal, contact time of 2 h, and pH ~ 5 and 6 for removal of Cu2+ and Cd2+, respectively. The adsorption process was well fitted with Langmuir and Freundlich isotherm models (higher R2), with trivial advantage for Freundlich approach. Kinetic studies showed that the adsorption of both Cd2+ and Cu2+ followed the pseudo-second-order. The current study demonstrated that the Ni-Al-CO3 LDH and their novel alginate-chitosan-based nanocomposite could be further tailored and used as efficient adsorbents for the uptake of heavy metals from wastewater.

The current study tested the antibacterial activity of layered double hydroxide (LDH), LDH-Doxycycline nanohybrid, Cobalt ferrite nanoparticles (NPs) and Cobalt ferrite-Chitosan nanohybrid against Gram-negative bacteria Escherichia coli. In addition, the study investigated the Cobalt ferrite NPs and Cobalt ferrite-Chitosan nanohybrids against Gram-positive bacteria Staphylococcus aureus. The nanoparticles and nanohybrids were synthesized by a chemical method and characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), and Fourier transformation Infra-red Spectroscopy (FTIR). Multi-point Brunauer-Emmet-Teller (BET) method determined the specific surface area while Barrett-Joyner-Halenda for (BJH) figured the corresponding specific pore volume and pore size and Zetasizer ranked the particle size distribution. Minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) measurements besides agar well diffusion method showed the antimicrobial activity of the nanoparticles. The results revealed no antibacterial activity of the LDH and Cobalt ferrite NPs alone. Meanwhile, the Cobalt ferrite-Chitosan nanohybrid and LDH-Doxycycline showed a high activity antibacterial effect.

Different morphologies of titania with different dimensions (0, 1 and 2 D) were prepared using hydrothermal technique and Au nanoparticles were deposited on its surface using photoreduction method. The obtained materials were characterized using X-ray diffraction, HRTEM and FESEM. The optical properties were studied for all morphologies before and after depositing of Au nanoparticles, a clear shift toward visible light absorption was confirmed after Au loading. Moreover, the surface area, pore size and pore volume were discussed and revealed that BET surface area was decreased after Au nanoparticles deposition on all morphologies. The prepared materials were applied as a photoanode for water splitting in alkaline media and the effect of titania dimension and Au deposition on the photocurrent were investigated. Au deposition on the surfaceof titania dramatically improves the performance of photocurrent generation during photoelectochemical electrolysis of water under simulated solar light irradiation. The titania dimension played a significant role on the value of photocurrent. Au modified nanotubes (1D) exhibit the highest photocurrent with high stability. The maximum photocurrent densities were 1.16, 0.63, 1.45, 2.97, 3.28, and 5.23 mA cm−2 at an applied potential of 1 V with 4.98, 2.01, 2.50, 3.47, 4.05, and 5.19 times increment for particles (0D), sheets (2D), tubes (1D), particles@Au, sheets@Au, and tubes@Au compared to its corresponding current density in dark respectively. Depositing of Au nanoparticles on titania, decreases the charge transfer resistance due to the surface plasmon resonance effect of Au nanoparticles leading to enhancement in the photoelectrochemical activity. TNT@Au photoanode had the longest electron pass due to the tubular form (1D) which help in charge separation.

Au decorated Co doped titanate nanotubes (TNT) was prepared for selective removal of methylene blue (MB) dye followed by selective photocatalytic degradation under solar light in presence of another highly concentrated dyes. The adsorption capacity of Co doped TNT was found to be increased with increasing Co content due to the increase in the number of pores and thus increase in surface area. Due to the high concentration of MB, Co doped TNT was completely covered by MB molecules and become difficult for light to Path though or absorbed by the Co doped TNT catalyst. In order to provide some photocatalytic characteristics for the catalyst, the doped TNTs were calcined to enhance the crystallinity and thus enhancing the photocatalytic activity, but the degradation rate was very low. Thus, another direction was started by reducing the adsorption ability of Co doped TNT through coating its surface by poly(allylamine hydrochloride), which changed the surface charge of the tubes to be positive and facilitate the electrostatic attachment of Au nanoparticles (15 nm). The synergetic effect of plasmonic Au nanoparticles in addition to adsorption and catalytic properties of Co doped TNT make the new composite promising catalyst for degradation of organic pollutants. It shows a good selectivity for adsorption and photocatalytic degradation of MB dye from dyes mixture. The obtained results indicate that Au decorated Co doped TNT will have a great effect on the development of selective environmental water treatment technologies specifically on flow challenges confronted by the wastewater treatment area.

Improved Hummer's method is widely used to prepare graphene oxide (GO), which is a precursor of graphene. Purification of as-prepared GO is challenging due to the used corrosive acidic media, large amounts of impurities are formed as byproducts during GO production, and the long time required for purification process. GO purification with traditional methods is difficult and time consuming. Novel methods for fast purification of as-prepared GO without pre-treatment was developed using commercially available hollow-fibre dialyzer (Phylther-1.7 m2). The dialyzer can be used several times in a crossflow filtration or dialysis process in the designed systems without deteriorating. The concentrations of impurities in GO suspension were monitored during purification process by measuring the ionic conductivity of the GO suspension. For process optimization, the factors affecting the purification methods were studied. The results showed that exfoliated GO can be purified in

Graphene oxide is a unique material that can be used for adsorption of radioactive waste because it contains various function groups such as epoxide, carbonyl, carboxyl and hydroxyl in addition to its high specific surface area. The as-prepared GO and the modified one (GO-chitosan composite) have been prepared then characterized and used as adsorbent for radioactive metal ions [Strontium, Sr(II)]. The results showed that the prepared materials are efficient adsorbents for removal of Sr(II) from water. The effect of contact time, pH and temperature on adsorption have been studied. The results indicated that the maximum adsorption capacity was about 140 and 179.6 mg/g for GO and GO-chitosan composite respectively. It was found that pH ~ 6 and temperature ~ 40 °C are the best condition for removal of Sr(II) from water. Two isotherm models (Langmuir and Freundlich) and three kinetic models (Pseudo-first-order, pseudo-second-order, and intra-particle particle diffusion model) have been applied. Based on the calculated isotherm parameters (R2), it can be concluded that Langmuir model fits the adsorption equilibrium data better than Freundlich model, the results also indicated that the second order kinetic model is the best representative for adsorption of Sr(II) on GO, Chitosan and GO-Chitosan. Based on the regressions of intraparticle diffusion model, experimental data showed that the adsorption process involved intraparticle diffusion, which was not the only rate-controlling step.

In this approach, two novel modified carbon paste sensors were assembled for potentiometric assay of sulpiride (SLP). One sensor is based on the ion pair of SLP–phosphotungstic acid and incorporation with multiwalled carbon nanotubes (MWCNTs) called MWCPE and the second sensor based on $\beta $ -cyclodextrin ( $\beta $ -CD) ionophore and sodium tetraphenylborate as anionic site additive called $\beta $ -CDCPE. Dibutyl phthalate was added as plasticizer. The characteristics of the suggested sensors showed responses in terms of Nernstian slopes 59 ± 0.7 and 59.5 ± 0.3 mV decade–1 in wide linear ranges from $1\times 10^{-6}$ to $-1 \times 10^{-2}$ mol·L–1 and from $1\times 10^{-5}$ to $- 1\times 10^{-2}$ mol·L–1 with low detection limits $3.5\times 10^{-7}$ and $5\times 10^{-6}$ mol·L–1 with very short response time 5 and 10 s and exhibit adequate operational long lifetime (22 and 17 weeks) for MWCPE and $\beta $ -CDCPE, respectively. Both sensors response were pH independent in the range of 2–8 at 25 °C. For studying the ion-to-electron transducing ability of MWCNTs and $\beta $ -CD on the sensor surface, the electrochemical impedance spectroscopy measurements were done. Scanning electron microscope and transmission electron microscope were used for studying the surface morphology of MWCPE sensor. The sensors showed adequate selectivity for SLP with respect to a large number of interfering species. Moreover, SLP ions were successfully determined in pure state, pharmaceutical preparations, and human urine with high accuracy and precision using these sensors.

In the present work, the study of semiconducting pure and Gd-doped cerium oxide (CeO2) nanostructures with application to gas sensors is addressed. Nanostructured powders were prepared by means of the co-precipitation technique. The powder has been examined using X-ray diffraction, transmission electron microscope and Raman spectroscopy to estimate the effect of Gd-doping on the properties of ceria. The particle size has been decreased by doping which indicates that the growth restriction rule of Gd in the ceria matrix. Also, a small shift in the peak position accompanied with more broadening in Raman analysis. Finally, the gas response of all powders has been tested for CO2 gas in temperature range from 200 to 400 °C. The Gd-doped CeO2 gas sensor has better sensitivity, good stability and lower operating temperature, with a detection fixed concentration of 800 ppm CO2 gas. The powder sensitivity was found to be maximum at 250 °C for Gd-doped ceria where the pure powder maximum response is predicted to be beyond 400 °C. Keywords: CeO2, Gd, Co-precipitation, CO2 gas sensor

Asymmetric supercapacitor (ASC) technique is introduced as promising and efficient energy storage devices due to their fast charging process and high-power density. A simple and green approach was introduced to fabricate mixed Co3O4/NiO intercalated reduced graphene oxide (rGO) nanosheets as ternary nanocomposite electrode materials for ASC applications. Herein, a Co3O4/NiO/rGO ternary nanocomposite was successfully fabricated using a hydrothermal method. The field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were utilized to elucidate the morphological shape and chemical surface analysis for the fabricated materials. Comparing the prepared samples, the ternary nanocomposite demonstrated a good capacitance value of 485.6 F/g at a current density of 2 A/g, good cycling stability, and low equivalent series resistance. The ASC was assembled using the Co3O4/NiO/rGO electrode as positive electrode and Fe2O3/rGO binary composite as the negative electrode. The proposed configuration design of ASC achieved a high energy density (37.83 W h /kg) at a high-power density of (750 W/kg) and a long life-time (86.9%) of over 6000 cycles. The ASC configuration design of Co3O4/NiO/rGO nanocomposites//Fe2O3/rGO opens new doors for promising green, economic, and efficient material-based supercapacitors.

The production of molecular hydrogen by photoelectrochemical dissociation (PEC) of water is a promising technique, which allows the direct transformation of solar energy into hydrogen, an energy vector acclaimed by the scientific community and policymakers. Hydrogen stores solar energy and will help overcome the energy crisis and associated environmental problems. Currently, the design and development of innovative photocatalysts with strong photoelectrochemical activity remain a major challenge, and the subject of intense research activity within the international scientific community. Here we describe the synthesis and photoelectrochemical properties of one-dimensional nanostructures of graphitic carbon nitride (1D-gC3N4) doped with phosphorus or sulfur (1D-P-gC3N4 &1D-S-gC3N4, respectively). A new synthesis method using supramolecular melamine, ammonium dihydrogen phosphate, and tri-thiocyanuric acid as precursors has been developed. The samples were characterized by powder-X Ray diffraction (p-XRD), X-Ray spectroscopy (EDS), transmission electron microscopy (TEM), Ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared spectra (FT-IR) and photoluminescence (PL) analysis. The activity towards the photo-oxidation of water was studied by linear scanning voltammetry (LSV). Compared to 3D material, the activity was found to be significantly improved, thanks in particular to the 1D morphology of gC3N4. It was further strengthened by doping with phosphorus and sulfur. The photo-oxidation mechanism of water was analyzed by photoelectrochemical impedance spectroscopy (PEIS). The measurements show that the resistance to charge transfer at the electrode/electrolyte interface can be greatly reduced by controlling the morphology of gC3N4, and that doping with phosphorus and sulfur also plays a positive role. The PEIS analysis makes it possible to demonstrate that the lifetime of the photo-generated electrons in 1D-gC3N4 is increased compared to 3D-gC3N4, and that doping with phosphorus or sulfur further improves it. The width of the forbidden bands and the position of the valence and conduction bands of the different materials were determined by Mott - Schottky type measurements.

The generation of renewable solar fuel through photoelectrochemical water splitting is hindered by the inability to identify the right material with the optimum optical, electrical and chemical characteristics. Herein, we demonstrate the ability to fabricate TiO2 hollow porous spheres (HPS)/graphene (Gr) hybrid composite photoanodes for use in solar fuel generation cells. The fabricated materials were characterized by X-ray diffraction, Raman spectroscopy, UV–Vis diffuse reflectance spectroscopy, photoluminescence (PL), scanning electron microscopy and electrochemical techniques. Upon the use of the TiO2 HPS/Gr photoanodes to split water photoelectrochemically under AM 1.5 illumination in 1.0 M KOH aqueous electrolyte, the performance increased with increasing the Gr content, showing a ten-fold increase in the photocurrent for the photoanode containing 5% Gr (1.449 mA cm−2) as compared to bare TiO2 HPS (0.143 mA cm−2). This enhancement is attributed to the effect of Gr in suppressing the recombination of charge carriers, as supported by the PL measurements and the decrease in the dark current upon the addition of Gr, which acts as an electron acceptor and transports electrons more efficiently. Moreover, the transient photocurrent (J–t) tests confirm the stability of the hybrid photoanodes.

Graphene oxide (GO) with high specific surface area was prepared and functionalized with ethylene diamine tetra-acetic acid (EDTA). The as-prepared GO and the functionalized one (GO-EDTA) were characterized using high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Raman spectroscopy. The as-prepared and EDTA funcationalized GO were applied as adsorbent to remove strontium(II) and cobalt(II) from water. The results indicated that the prepared materials are efficient adsorbents for strontium(II) and cobalt(II) removal. The adsorption of CoII and SrII under effects of contact time, temperature, and pH was investigated It is concluded that the maximum adsorption capacities of GO for CoII and SrII were about 168 and 140 mg·g–1, whereas of GO-EDTA the values were about 197 and 158 mg·g–1, respectively. It is indicated that pH 6 and temperature 40 °C are the best condition for CoII and SrII removal from water. The application of Langmuir and Freundlich isotherms indicated that Langmuir isotherm is best fit for CoII and SrII equilibrium adsorption. Adsorption kinetics were studied by applying pseudo first-order, pseudo second-order, and intraparticle diffusion models on the experimental data. The results proved that pseudo second-order model is the best represented adsorption kinetics. Appling the intraparticle diffusion regressions on the experimental data indicated that intraparticle diffusion involved in adsorption process, which was not the only rate-controlling step.

CeO2, Sm and Gd doped CeO2 were synthesized using the hydrothermal route. The influence of synthesis conditions on the crystal structure, particle size and microstructure was investigated. The prepared nanoparticles were characterized using X-ray powder diffraction, FT-Raman spectroscopy, transmission electron microscopy and scanning electron microscopy. The photo-catalytic degradation of methylene blue was examined under UV light using the prepared nanoparticles at different conditions (pH, dye concentration, catalyst dosage). The photo-catalytic activity of CeO2 was kinetically enhanced by trivalent cations (Gd+3 and Sm+3) doping. The results displayed the excellent catalytic activity of the Gd doped CeO2 as compared to that Sm doped CeO2 and the undoped one. The degradation pathways of MB were followed using liquid chromatography/mass spectroscopy (LC/MS), it was found that MB was degraded completely into safe byproducts. The total organic carbon content measurements confirmed the results obtained by LC/MS.

A new fundamental mechanism for reliable engineering of zinc oxide (ZnO) nanorods to nanoplatelets grafted Mo8O23-MoO2 mixed oxide with controlled morphology, composition and precise understanding of the nanoscale reaction mechanism was developed. These hybrid nanomaterials are gaining interest due to their potential use for energy, catalysis, biomedical and other applications. As an introductory section, we demonstrate a new expansion for the concept ‘materials engineering’ by discussing the fabrication of metal oxides nanostructures by bottom-up approach and carbon nanoparticles by top-down approach. Moreover, we propose a detailed mechanism for the novel phenomenon that was experienced by ZnO nanorods when treated with phosphomolybdic acid (PMA) under ultra-sonication stimulus. This approach is expected to be the basis of a competitive fabrication approach to 2D hybrid nanostructures. We will also discuss a proposed mechanism for the catalytic deposition of Mo8O23-MoO2 mixed oxide over ZnO nanoplatelets. A series of selection rules (SRs) which applied to ZnO to experience morphology transition and constitute theory for morphology transition engineering (TMTE) will be demonstrated through the article, besides a brief discussion about possibility of other oxides to obey this theory.

The lack of cost-effective techniques for harvesting microalgae is a major challenge for microalgal application in wastewater treatment plants as well as large-scale production of microalgae. Here, a novel approach for the recovery of Chlorella vulgaris biomass using zinc aluminum-layered double hydroxide (ZnAl-LDH) nanosheets is introduced. ZnAl-LDHs are a green “eco-friendly” and efficient flocculent with capacity up to 0.521 g g−1. The adsorption and agglomeration of microalgal cells onto LDH layers were elucidated and confirmed. Different factors affecting flocculation efficiency including LDH concentration, algae concentration, pH, temperature, and time were studied and statistically optimized using the Plackett–Burman design. The best flocculation efficiency (96%) was obtained at the following conditions: pH 6, 35 °C temperature, and microalgae concentration range from 4.8 to 8.7 mg L−1 based on chlorophyll a content, 1 g L−1 LDH dosage and sedimentation time of 1 min. LDH concentrations higher than 1 g L−1 had no positive effect on the efficiency of the flocculation process.

Novel multiwalled carbon nanotubes/ Fe-Co doped titanate nanotubes nanocomposite (MWCNTs/Fe-Co doped TNTs) facilitated the charge transfer and enhanced sensitivity and selectivity. Herein, three novel modified carbon paste sensors (CPSs) based on MWCNTs (sensor I), Fe-Co doped TNTs (sensor II) and MWCNTs/Fe-Co doped TNTs composite (sensor III) were fabricated for a simple, low cost and high accuracy electrochemical method for the potentiometric determination of sulpiride (SLP). The sensors exhibited excellent Nernstian slopes 57.1 ± 0.4, 56 ± 0.5 and 58.8 ± 0.2 mV decade−1 with detection limits (DL) 7.6 × 10−7, 1.58 × 10−6 and 8.7 × 10−8 mol L−1, quantification limits (QL) 2.5 × 10−6, 5.2 × 10−6 and 2.9 × 10−7 mol L−1 for a long lifetime 20, 18, and 25 weeks for sensors (I), (II), and (III), respectively. The modified sensor (III) was applicable by measuring the concentration of spiked SLP in pure solutions, pharmaceutical products, human urine, and real water samples. The proposed method can be used as an important analytical tool in the quality control of the pharmaceutical industry.

A key challenge in photoelectrochemical water splitting is to fabricate nanostructured photoelectrodes with desirable properties. Herein, Ni doped BaTiO3 hollow spheres (HS) supported on reduced graphene oxide (RGO) nanocomposite were successfully synthesized by aerosol spray drying method. Former spheres consisted of small nanoparticles with size 5–20 nm possessing high porosity and large area. Characterizations were done by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). Ni doped BaTiO3 HS/RGO nanocomposites as photoanodes exhibited an enhanced photoelectrochemical performance and long-term stability compared to BaTiO3 HS and BaTiO3 HS/RGO. The photocurrent density of Ni doped BaTiO3 HS/RGO photoanode revealed 8.14 μA cm−2 which is 37% more than BaTiO3 HS. From electrochemical impedance spectroscopy (EIS) analysis, Ni doped BaTiO3 HS/RGO exhibited the lowest charge transfer resistance in comparison with BaTiO3 HS and BaTiO3 HS/RGO which leads to enhancement in the electrocatalytic activity. The successful doping of BaTiO3 HS by Ni and its loading over RGO increases the separation rate of photogenerated electrons and holes and improved the light harvesting. Ni doped BaTiO3 HS/RGO as photo-electrocatalyst exhibits excellent activity toward water oxidation capability and presents a new approach for high-efficient future photo-electrocatalysis.

Manganite containing La is a promising perovskite material as it has wide range of applications. In this piece of work, nanoparticles of La1−xAgxMnO3 samples (0.00 ≤ x ≤ 0.09) were synthesized using wet chemical method. The samples were characterized by thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), differential thermal analysis (DTA), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), infrared spectroscopic (FT-IR), and differential scanning calorimetry (DSC). The XRD study showed that all samples adopted the rhombohedral hexagonal structure with a space group of R 3 c. The HR-TEM/FE-SEM images showed that the perovskite structure were successfully obtained. Investigation of the magnetic properties was conducted in a wide range of temperature to confirm the ferromagnetic-paramagnetic (FM-PM) presence around Curie temperature (Tc ≈ 270 K). The shift of the Curie point to larger values was clearly observed for the samples by increasing the silver contents.

There are two main industrial techniques of water electrolysis operating under near-ambient temperature and pressure conditions: alkaline water electrolysis which uses a liquid electrolyte based on an aqueous solution of potassium hydroxide [1] and PEM water electrolysis [2] which uses a solid electrolyte made of a proton-conducting polymer. Both technologies present a set of strengths and weaknesses in view of practical application in the industry sector. The objective of this communication is to highlight the differences and similarities in terms of design (cell and stack) and balance-of-plant, and to present in a critical way what are these advantages and disadvantages, from a scientific viewpoint (that of materials science, especially for the selection of electrocatalysts), from a technological viewpoint (stack design and balance-of-plant) and from an economic viewpoint (comparative analysis of capex and opex). The discussion will take into account the situation which prevails on machines at the MW-scale. Particular attention will be paid to the ability of these machines to operate under transient conditions, in particular with a view to providing services to the electricity network. Several performance indicators such as the flexibility and reactivity of machines to the demands of network operators will be used to carry out this comparison. A detailed analysis of the existing limitations will make it possible to define a set of development perspectives highlighting possible complementarities. [1] N. Guillet and P. Millet, in : Hydrogen Production: by Water Electrolysis’, chapter 4, Alkaline Water electrolysis, A. Godula-Jopek, D. Stolten Editors, Wiley-VCH (2015). [2] D. Bessarabov and P. Millet in: PEM water electrolysis, “Hydrogen and Fuel Cells Primers”, B.G. Pollet Editor, 1st Edition, Elsevier (2018).

To find proper non-expensive electrocatalyst materials for ethanol oxidation is a big challenge. Transition metals catalysts are considered as the ideal solution for the electro-oxidation of ethanol. Nickel demonstrates high electrocatalytic activity that makes it the predominant candidate for ethanol electro-oxidation. In this study, the electrocatalytic activity of nickel was improved by the synergetic effect of a co-catalyst (Tungsten based nanomaterial) and a proper support (carbon nanofibers). Due to its high adsorption capacity, a nanomaterial of carbonaceous fibers has been used as support for Ni -based electrocatalysts. Different contents of tungsten incorporated in Ni-doped carbon nanofibers (Ni/C) were prepared and the effect of different parameters such as morphology, W content, calcination temperature, ethanol concentration and reaction temperature on the electro-oxidation performance of ethanol have been studied. At 2.0 M ethanol concentration and 25 wt% tungsten content, the electro-oxidation current density of nanoparticles and nanofibers morphologies were 28.23 and 99 mA.cm−2, respectively. The nanofibers calcinated at 1000 °C shows the highest electrocatalytic activity compared to the samples calcinated at 700 and 850 °C. The sample containing 10 wt% tungsten and calcinated at 1000 °C gives a current density of 2.5 times higher than of the sample prepared at 850 °C. The sample of 25 wt% tungsten incorporated in Ni-doped carbon nanofibers shows the best performance towards electro-oxidation of ethanol in basic medium where a current density of 99.3 ± 0.02 mA.cm−2 was obtained. This work will open the window towards a new non-expensive electrocatalyst in the ethanol electro-oxidation process.

Three-dimensional (3D) structures are currently a topic of considerable interest due to their extraordinary properties. In this work, a 3D hybrid nanocomposite nickel-chromium layered double hydroxide (NiCr-LDH) was in-situ synthesized on different concentrations of reduced graphene oxide (rGO) using a microwave-assisted method. The structural and morpholological analysis of the as-prepared nanocomposites were characterized by XRD, SEM, TEM, FTIR and BET. The nanocomposite contains the highest amount of rGO (200 mg) shows a 3D sand rose-like structure which considered as a benifit for electrocatalytic reactions. The 3D structure of the hybrid NiCr-LDH⁄rGO nanocomposites exhibited much higher performance for methanol oxidation than the pure NiCr-LDH catalyst where the nanocomposites surface became more open, thus providing minor resistance for mass transport. Thus, an electron pathway can be easily formed and a network of stress transfer can be also presented. Using 3 M methanol at scan rate of 60 mVs−1, the obtained current density was found to be 0.54, 0.97, 1.39 and 2.22 mA/cm2 for G0-LDH, G50-LDH, G100-LDH and G200-LDH, respectively. These enhancements confirmed that the 3D structure of the NiCr-LDH with rGO can guarantee an efficient use of the catalyst. Furthermore, the sand rose-like structure of G200-LDH sample exhibited the lowest onset potential 0.3 V. This work will open the door toward fabrication of 3D sand rode-like structure to be used in different electrocatalytic reactions.

Photoelectrochemical (PEC) water splitting is a promising strategy to improve the efficiency of oxygen evolution reactions (OERs). However, the efficient adsorption of visible light as well as long-term stability of light-harvesting electrocatalysis is the crucial issue in PEC cells. Metal&ndash, organic framework (MOF)-derived bimetallic electrocatalysis with its superior performance has wide application prospects in OER and PEC applications. Herein, we have fabricated a nickel and iron bimetallic organic framework (FeNi-MOF) deposited on top of anodized TiO2 nanotube arrays (TNTA) for PEC and OER applications. The FeNi-MOF/TNTA was incorporated through the electrochemical deposition of Ni2+ and Fe3+ onto the surface of TNTA and then connected with organic ligands by the hydrothermal transformation. Therefore, FeNi-MOF/TNTA demonstrates abundant photoelectrocatalytic active sites that can enhance the photocurrent up to 1.91 mA/cm2 under 100 mW/cm2 and a negligible loss in activity after 180 min of photoreaction. The FeNi-MOF-doped photoanode shows predominant photoelectrochemical performance due to the boosted excellent light-harvesting ability, rapid photoresponse, and stimulated interfacial energy of charge separation under the UV-visible light irradiation conditions. The results of this study give deep insight into MOF-derived bimetallic nanomaterial synthesis for photoelectrochemical OER and provide guidance on future electrocatalysis design.

Ruptured tubular structured graphitic-carbon nitride (RT g-C3N4) was prepared, followed by in-situ growth of carbonate-intercalated ZnCr layered double hydroxide (LDH) on its surface by the co-precipitation method. The fabricated composites contain varying amounts of the LDH. An increase in the specific surface area of the g-C3N4/LDH3 composite (103.74 m2/g) was observed as compared to RT g-C3N4 (7.55 m2/g) and pristine LDH (11.26 m2/g). The formation, morphology and chemical composition of the pristine RT g-C3N4, pristine LDH and composites were examined by powdered-X-ray diffraction (p-XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) techniques. Optical measurements by ultraviolet-visible (UV) diffuse reflectance spectroscopy revealed that the band gap of the composites can be tuned by varying the LDH concentration in the composite. The ability towards the separation of photo-generated electron-hole pairs was examined by photoluminescence (PL) and the curves of transient photo-current with time. Mott-Schottky measurements were carried out to determine the flat band potential. Finally, the photoelectrocatalytic activity represented by measurements of transient photo-current with time (i-t curve), electrochemical impedance spectroscopy, and linear sweep voltammetry (i-v curve) was examined.

Results reported in this research paper are related to the photo-oxidation of water into molecular oxygen, using n-type photoelectrodes operated with the support of an external electric bias. These photoanodes are made of 1 cm2 rectangular glass substrates, surface-covered by thin films of conductive fluorine-doped tin oxide (FTO). Thin mats of titanium dioxide nanorods (TDNRs) have been deposited over the FTO surfaces. The TDNRs have then been sensitized by surface deposition of cobalt dodecahedral Zeolitic Imidazolate Framework (ZIF-67) metal organic framwork (MOF). ZIF-67 has been deposited using a two-step process: (i) deposition of cobalt hydroxide by chronoamperometry; (ii) in-situ transformation of cobalt hydroxide into ZIF-67 by chemical reaction with a solution of 2-methylimidazol. The amount of ZIF-67 has been adjusted by monitoring the duration of the electro-reduction step. The photoanodes have been characterized by scanning electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and UV–Vis absorption spectroscopy. The photoelectrochemical responses of the different photoanodes have been measured under chopped illumination conditions. Dark currents as high as 100–150 μA/cm2 and photocurrents of only 10–15 μA/cm2 have been measured on fresh samples with large MOF contents, at an operating potential of +1.0 V vs. saturated calomel electrode, 25 °C, under UV–Vis irradiation. No dark current and photocurrents close to 40 μA/cm2 have been measured on samples with low MOF contents. The dynamics of charge transfer leading to the formation of molecular oxygen has been analyzed by photoelectrochemical impedance spectroscopy to understand the interplay between the OER electroactivity and photoelectroactivity. It is shown that large MOF contents induce two contradictory effects: the first one (faster charge transfer kinetics) is desirable while the second one (faster charge recombination kinetics) is not desirable. Only limited MOF contents are beneficial to maximize the photocurrent density.

International audience; In this work, we report a novel photocatalyst based on boron and nitrogen co-doped TiO2 rutile (1 1 0) honeycomb structures. The photocatalyst has been prepared by simultaneously oxidizing and doping a Ti-foil substrate at 750 degrees C. The unit cell volume and the crystallite size of grown TiO2 films were measured by Rietveld refinement analysis. The co-doping by boron and nitrogen was achieved simultaneously with the oxidation of the titanium, resulting in a rutile (1 1 0) textured TiO2 film. X-ray photoelectron spectroscopy analysis revealed the presence of Ti-O-N and Ti-O-B-N bonds, and the presence of crystal defects in the lattice was detected and displayed by Raman spectroscopy. The water photo-oxidation properties have been measured as well, and the photocurrent of the B/N co-doped rutile sample prepared reached 270 mu A/cm(2) at 1 V under visible light and was stable in time. The efficient visible light absorption properties of the fabricated nanomaterial were attributed to the presence of oxygen vacancies and the introduction of impurity levels, as well as to synergistic effects between the introduced boron and nitrogen elements. The results presented demonstrate a new route for the preparation of TiO2 based catalysts, and open prospects for the photocatalysis community.

Herein, we report sunlight-activated photo-catalysis response of direct current radio frequency (DC/RF)-sputtered Ag–CuO nanoparticles thin films. We have adopted this approach for facile removal and easy recovery of thin films after use. Ag was incorporated at 2.5 and 5.4 wt% with reference to pure CuO. Structural analysis through X-ray diffraction showed successful incorporation of Ag into the CuO lattice. Surface morphological observation was carried out using a field emission scanning electron microscope, which showed a uniform deposition of the subjected thin films. The surface composition and change in the chemical state of pure and incorporated thin films were studied by X-ray photoelectron spectroscopy. In addition to structural and surface analysis, optical band gap evolution was also studied through UV–visible spectroscopy. The obtained results reflected that optical band gap decreased from 1.84 to 1.77 and 1.61 eV for 0, 2.5 and 5.4 wt% Ag, respectively. Methylene blue dye was used to investigate the photo-catalytic degradation response of deposited thin films in sunlight. Furthermore, the effect of pH and dye concentration was also taken into account. The degradation results indicate the acceleration of degradation process with the Ag incorporation into CuO lattice. Moreover, the pH also contributes positively to the degradation progression. This research study could provide a platform to understand and develop metal oxide thin films with an efficient photo-catalytic response in sunlight.

A comprehensive overview and description of crumpled graphene explored in recent years for energy storage applications is presented. Although graphene is known as one of the best electronic materials, preparation of crumpled graphene has been less explored. This article selectively aims to present an overview of the advancement of research in crumpled graphene, in the areas of preparation and applications especially in energy storage, such as supercapacitors and lithium ion batteries. When graphene is transformed ino the crumpled form, the resulting material can give superior capacitance due to its unique properties like extremely high specific surface area, high conductivity and stability against graphitization (aggregation-resistant) compared to those of flat graphene sheets which tend to aggregate and thus lead to a dramatic decrease in the surface area, leading to poor capacitance.