Preparation and Photocatalytic Performance of TiO2 Nanowire-Based Self-Supported Hybrid Membranes.

Nowadays, the use of hybrid structures and multi-component materials is gaining ground in the fields of environmental protection, water treatment and removal of organic pollutants. This study describes promising, cheap and photoactive self-supported hybrid membranes as a possible solution for wastewater treatment applications. In the course of this research work, the photocatalytic performance of titania nanowire (TiO2 NW)-based hybrid membranes in the adsorption and degradation of methylene blue (MB) under UV irradiation was investigated. Characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffractometry (XRD) were used to study the morphology and surface of the as-prepared hybrid membranes. We tested the photocatalytic efficiency of the as-prepared membranes in decomposing methylene blue (MB) under UV light irradiation. The hybrid membranes achieved the removal of MB with a degradation efficiency of 90% in 60 min. The high efficiency can be attributed to the presence of binary components in the membrane that enhanced both the adsorption capability and the photocatalytic ability of the membranes. The results obtained suggest that multicomponent hybrid membranes could be promising candidates for future photocatalysis-based water treatment technologies that also take into account the principles of circular economy.

The Effect of the Reducing Sugars in the Synthesis of Visible-Light-Active Copper(I) Oxide Photocatalyst.

In the present work, shape tailored Cu2O microparticles were synthesized by changing the nature of the reducing agent and studied subsequently. d-(+)-glucose, d-(+)-fructose, d-(+)xylose, d-(+)-galactose, and d-(+)-arabinose were chosen as reducing agents due to their different reducing abilities. The morpho-structural characteristics were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS), while their photocatalytic activity was evaluated by methyl orange degradation under visible light (120 min). The results show that the number of carbon atoms in the sugars affect the morphology and particle size (from 250 nm to 1.2 µm), and differences in their degree of crystallinity and photocatalytic activity were also found. The highest activity was observed when glucose was used as the reducing agent.

Photocatalytic Crystalline and Amorphous TiO2 Nanotubes Prepared by Electrospinning and Atomic Layer Deposition.

In this work core/shell composite polymer/TiO2 nanofibers and from those TiO2 nanotubes were prepared. First, poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) fibers were synthetized by electrospinning. They were covered with a 100 nm thick amorphous TiO2 layer by atomic layer deposition at 50 °C. Later the polymer core was removed by two different methods: dissolution and annealing. In the case of dissolution in water, the as-prepared TiO2 nanotubes remained amorphous, while when annealing was used to remove the polymers, the TiO2 crystallized in anatase form. Due to this, the properties of amorphous and crystalline TiO2 nanotubes with exactly the same structure and morphology could be compared. The samples were investigated by SEM-EDX, ATR-IR, UV-Vis, XRD and TG/DTA-MS. Finally, the photocatalytic properties of the TiO2 nanotubes were studied by decomposing methyl-orange dye under UV light. According to the results, crystalline anatase TiO2 nanotubes reached the photocatalytic performance of P25, while amorphous TiO2 nanotubes had observable photocatalytic activity.

New Insights into The Photoactivity of Shape-Tailored BiVO4 Semiconductors via Photocatalytic Degradation Reactions and Classical Reduction Processes.

In the present study, additive-free, pH-driven, hydrothermal crystallization was used to obtain shape-tailored monoclinic BiVO4 photocatalysts. The as-prepared BiVO4 products were systematically characterized, uncovering their crystallographic, morphologic and optical properties, while their applicability was verified in the visible light-driven photodegradation of oxalic acid and rhodamine B. Monoclinic clinobisvanite was obtained in most cases, with their band gap values located between 2.1 and 2.4 eV. The morphology varied from large, aggregated crystals, individual microcrystals to hierarchical microstructures. It was found that the degradation efficiency values obtained in the case of oxalic acid were directly related to the presence of (040) crystallographic plane, while the degradation of rhodamine B was partially independent by the presence of this structural feature. The importance of (040) crystallographic plane was also demonstrated via the reduction of Cu2+ to Cu, by analyzing the Raman spectra of the Cu containing samples, the mean primary crystallite size of Cu and Cu content. Furthermore, the presence of (040) crystallographic plane was directly proportional with the hydrodynamic properties of the powders as well.

A Review on BiOX (X= Cl, Br and I) Nano-/Microstructures for Their Photocatalytic Applications.

In the recent past, bismuth oxyhalides (BiOX) have been widely used for the photocatalytic degradation of the organic pollutants and other environmental remediation because of their higher stability, economic viability, nontoxicity and effective charge separation. We begin with the review of the different approaches adopted so far for BiOX (X = Cl, Br, and I) synthesis and a study of their photocatalytic performances under UV and visible light towards the various organic as well as inorganic pollutants. Later on, a study on further enhancement of the efficiency of BiOX under UV and visible light irradiation using recent advancements would be presented. The new approaches involve controlled morphology by forming composite and hybrid materials with other semiconductors and also doping with other metals and nonmetals that would undoubtedly be beneficial in the interfacial charge transfer and efficient inhibition of the photo-generated species. Herein, we would also exploit the recent developments in the research strategies for enhancing photocatalytic activity of BiOX.

Preparing SnO2/MWCNT Nanocomposite Catalysts via High Energy Ball Milling.

Ball milling method was used to fabricate successfully tin dioxide (SnO2)/multi-walled carbon nanotubes nanocomposite materials using SnCl2 ×2H2O as precursor together with soda and salt as admixture. The as-prepared materials were characterized by transmission electron microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, Raman microscopy, and X-ray diffraction techniques. Observations revealed that applying both soda and salt are advantageous for increasing dispersity of tin dioxide nanoparticles on the surface of carbon nanotubes. These multi-walled carbon nanotube-based composites are promising candidates as thick film gas sensors or catalysts. Results indicate that SnO2/MWCNT composites can be achieved under solvent free dry conditions, too.

Electron Microscopy Investigation of Coated Multiwall Carbon Nanotubes Prepared by Reactive Ball Milling.

Homogeneous and stable inorganic coating of SiO2, Al2O3 and TiO2 was obtained on the surface of multiwall carbon nanotubes (MWNTs) by mechanically mixing them with precursor compounds in a planetary ball mill and by subsequent hydrolysis. Detailed studies by means of transmission and scanning electron microscopy revealed that the milling time as well as the number of balls significantly affects the homogeneity of the layer formed. Our results demonstrate that planetary ball milling can be an effective and low-cost process for the production of homogenous coating of oxides on MWNTs in a large-scale.

Plant leaf extracts as photocatalytic activity tailoring agents for BiOCl towards environmental remediation.

The inducement of plant leaf extracts for the synthesis of various nanostructures has intrigued researchers across the earth to explore the mechanisms of biologically active compounds present in the plants. Herein, a green modified hydrolysis route has been employed for the synthesis of bismuth oxychloride i.e. BiOCl-N, BiOCl-T and BiOCl-A using plant extracts of Azadirachta indica (Neem), Ocimum sanctum (Tulsi), and Saraca indica (Ashoka), and; simultaneously, without plant extract (BiOCl-C), respectively. The as-prepared samples were examined by several microscopic and spectroscopic techniques which revealed that the biosynthesized BiOCl attained certain favorable features such as hierarchical nano-flower morphology, higher porosity, higher specific surface area and narrower band gap compared to BiOCl-C. The degradation of methyl orange (MO) and bisphenol A (BPA) using biosynthesized BiOCl were improved by 21.5% within 90 min and 18.2% within 600 min under visible light irradiation, respectively. The photocurrent response, electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) studies indicated the effective inhibition of the electron-hole pair recombination and enhanced photocatalytic activity of the biosynthesized BiOCl.

Comparison of various advanced oxidation processes for the degradation of phenylurea herbicides.

Various types of advanced oxidation processes (AOPs), such as UV photolysis, ozonation, heterogeneous photocatalysis and their combinations were comparatively examined at the same energy input in a home-made reactor. The oxidative transformations of the phenylurea herbicides fenuron, monuron and diuron were investigated. The initial rates of transformation demonstrated that UV photolysis was highly efficient in the cases of diuron and monuron. Ozonation proved to be much more effective in the transformation of fenuron than in those of the chlorine containing monuron and diuron. In heterogeneous photocatalysis, the rate of decomposition decreased with increase of the number of chlorine atoms in the target molecule. Addition of ozone to UV-irradiated solutions and/or TiO2-containing suspensions markedly increased the initial rates of degradation. Dehalogenation of monuron and diuron showed that each of these procedures is suitable for the simultaneous removal of chlorinated pesticides and their chlorinated intermediates. Heterogeneous photocatalysis was found to be effective in the mineralization.

Experimental and theoretical aspects of the growth of vertically aligned CNTs by CCVD on AZO substrate.

An efficient and reproducible growth of vertically aligned carbon nanotubes by CCVD requires accurate and specific setting of the synthesis parameters and the properties of catalyst thin layers. In this work, the growth of vertically aligned carbon nanotubes onto AZO (= aluminum doped zinc oxide) glass substrate covered by Al2O3 and Fe-Co catalyst layer system is presented. Investigation of the effect of catalyst composition and synthesis temperature on CVD growth revealed the optimum condition of the synthesis. The analysis of as-prepared samples by SEM, TEM and Raman spectroscopy was carried out to prove the structure and quality of carbon deposit. Theoretical considerations have supported speculative ideas about the role of the support layer, the transformation of the catalyst layer in the presence of hydrogen gas and the growth mechanism of carbon nanotubes. The mechanism of CNT growth is modelled and the order of magnitude of experimentally observed vertical linear growth rate of CNT (several nm/s) is reproduced.

Thermodynamic analysis of mono and hybrid nanofluid effect on the photovoltaic-thermal system performance: A comparative study.

The energy and exergy efficiency of a photovoltaic thermal (PV/T) system at various volume fractions is investigated with mono TiO2 nanofluid and new hybrid TiO2-Fe2O3 nanofluid. Serpentine tubes soldered on an absorbing plate attached to the rear of the PV module have been proposed to evaluate the effect of nanofluids on the PV/T temperature reduction, energy produced, and exergy losses. The study compared energy and exergy with previous studies and delivered an economic analysis to confirm the feasibility of applying nanofluids. The results indicated that using TiO2-Fe2O3 nanofluid reduced the PV cell's temperature by 42.19% compared to water, TiO2 nanofluid, which increased the electrical power by 74.5% and 46.22% when cooling by mono and hybrid nanofluid at 0.3 vol%. The PV/T system's maximum thermal and electrical efficiency recorded with mono and hybrid nanofluids was 34.6%, 8.44%, 47.2%, and 12.62%, respectively. Dispersion of hybrid nanocomposite in DI water has enhanced the Nu number and HTC by 42.72% and 23% higher than mono nanofluid, which improved the exergy efficiency of the PV/T system by 14.89%. A better payback period was achieved with a hybrid nanofluid by 54 days with reduced exergy losses by 45.5% and entropy generation by 86.29%.

Outstanding Separation Performance of Oil-in-Water Emulsions with TiO2/CNT Nanocomposite-Modified PVDF Membranes.

Membrane filtration is an effective technique for separating micro- and nano-sized oil droplets from harmful oil-contaminated waters produced by numerous industrial activities. However, significant flux reduction discourages the extensive application of this technology; therefore, developing antifouling membranes is necessary. For this purpose, various titanium dioxide/carbon nanotube (TiO2/CNT) nanocomposites (containing 1, 2, and 5 wt.% multi-walled CNTs) were used for the modification of polyvinylidene fluoride (PVDF) ultrafilter (250 kDa) membrane surfaces. The effects of surface modifications were compared in relation to the flux, the filtration resistance, the flux recovery ratio, and the purification efficiency. TiO2/CNT2% composite modification reduced both irreversible and total filtration resistances the most during the filtration of 100 ppm oil emulsions. The fluxes were approximately 4-7 times higher compared to the unmodified PVDF membrane, depending on the used transmembrane pressure (510, 900, and 1340 L/m2h fluxes were measured at 0.1, 0.2, and 0.3 MPa pressures, respectively). Moreover, the flux recovery ratio (up to 68%) and the purification efficiency (95.1-99.8%) were also significantly higher because of the surface modification, and the beneficial effects were more dominant at higher transmembrane pressures. TiO2/CNT2% nanocomposites are promising to be applied to modify membranes used for oil-water separation and achieve outstanding flux, cleanability, and purification efficiency.

Enhanced Antifouling in Flat-Sheet Polyphenylsulfone Membranes Incorporating Graphene Oxide-Tungsten Oxide for Ultrafiltration Applications.

In this study tungsten oxide and graphene oxide (GO-WO2.89) were successfully combined using the ultra-sonication method and embedded with polyphenylsulfone (PPSU) to prepare novel low-fouling membranes for ultrafiltration applications. The properties of the modified membranes and performance were investigated using Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), contact angle (CA), water permeation flux, and bovine serum albumin (BSA) rejection. It was found that the modified PPSU membrane fabricated from 0.1 wt.% of GO-WO2.89 possessed the best characteristics, with a 40.82° contact angle and 92.94% porosity. The permeation flux of the best membrane was the highest. The pure water permeation flux of the best membrane showcased 636.01 L·m-2·h-1 with 82.86% BSA rejection. Moreover, the membranes (MR-2 and MR-P2) manifested a higher flux recovery ratio (FRR %) of 92.66 and 87.06%, respectively, and were less prone to BSA solution fouling. The antibacterial performance of the GO-WO2.89 composite was very positive with three different concentrations, observed via the bacteria count method. These results significantly overtake those observed by neat PPSU membranes and offer a promising potential of GO-WO2.89 on activity membrane performance.

Novel partially cross-linked nanoparticles graft co-polymer as pore former for polyethersulfone membranes for dyes removal.

A newly developed water-soluble polymeric nano-additive termed "partially cross-linked nanoparticles graft copolymer (PCLNPG)" has been successfully synthesized and harnessed as a pore former for modifying a polyethersulfone ultrafiltration membrane for dyes removal. The PCLNPG content was varied in the PES polymeric matrix aiming to scrutinize its impact on membrane surface characteristics, morphological structure, and overall performance. Proposed interaction mechanism between methylene blue (MB), methyle orange (MO), and malachite green (MG) dyes with PES membrane was presented as well. Hydrophilicity and porosity of the novel membrane increased by 18 and 17 %, respectively, when manufactured with a 3 Wt. % PCLNPG, according to the findings. Besides this, the disclosed increased porosity, rather than the hydrophilic properties of the water-soluble PCLNPG, was the principal cause of the diminished contact angle. Meanwhile, raising the PCLNPG content in the prepared membrane made worthy shifts in its structure. A sponge-like region was materialized near the bottom surface as well. The membrane's pure water flux (PWF) synthesized with 3 Wt.% PCLNPG recorded 628 LMH, which is estimated 3.95 fold the pristine membrane. MG, MB, and MO dyes were rejected by 90.6, 96.3, and 97.87 %, respectively. These findings showed that the performance characteristics of the PES/PCLNPG membrane make it a potentially advantageous option to treat the textile wastewater.

Porous silicon/photosynthetic reaction center hybrid nanostructure.

The purified photosynthetic reaction center protein (RC) from Rhodobacter sphaeroides R-26 purple bacteria was bound to porous silicon microcavities (PSiMc) either through silane-glutaraldehyde (GTA) chemistry or via a noncovalent peptide cross-linker. The characteristic resonance mode in the microcavity reflectivity spectrum red shifted by several nanometers upon RC binding, indicating the protein infiltration into the porous silicon (PSi) photonic structure. Flash photolysis experiments confirmed the photochemical activity of RC after its binding to the solid substrate. The kinetic components of the intraprotein charge recombination were considerably faster (τ(fast) = 14 (±9) ms, τ(slow) = 230 (±28) ms with the RC bound through the GTA cross-linker and only τ(fast) = 27 (±3) ms through peptide coating) than in solution (τ(fast) = 120 (±3) ms, τ(slow) = 1387 (±2) ms), indicating the effect of the PSi surface on the light-induced electron transfer in the protein. The PSi/RC complex was found to oxidize the externally added electron donor, mammalian cytochrome c, and the cytochrome oxidation was blocked by the competitive RC inhibitor, terbutryne. This fact indicates that the specific surface binding sites on the PSi-bound RC are still accessible to external cofactors and an electronic interaction with redox components in the aqueous environment is possible. This new type of biophotonic material is considered to be an excellent model for new generation applications at the interface of silicon-based electronics and biological redox systems designed by nature.

Experimental Investigation of Rheological Properties and Thermal Conductivity of SiO2-TiO2 Composite Nanofluids Prepared by Atomic Layer Deposition.

In the current research, surface-modified SiO2 nanoparticles were used upon immersion in an applied base fluid (ethylene glycol:water = 1:1). The atomic layer deposition method (ALD) was introduced to obtain a thin layer of TiO2 to cover the surface of SiO2 particles. After the ALD modification, the TiO2 content was monitored by energy dispersive X-ray spectroscopy (EDS). Transmission electron microscopy (TEM) and FT-IR spectroscopy were applied for the particle characterization. The nanofluids contained 0.5, 1.0, and 1.5 volume% solid particles and zeta potential measurements were examined in terms of colloid stability. A rotation viscosimeter and thermal conductivity analyzer were used to study the nanofluids' rheological properties and thermal conductivity. These two parameters were investigated in the temperature range of 20 °C and 60 °C. Based on the results, the thin TiO2 coating significant impacted these parameters.

Classification of Nanomaterials and the Effect of Graphene Oxide (GO) and Recently Developed Nanoparticles on the Ultrafiltration Membrane and Their Applications: A Review.

The emergence of mixed matrix membranes (MMMs) or nanocomposite membranes embedded with inorganic nanoparticles (NPs) has opened up a possibility for developing different polymeric membranes with improved physicochemical properties, mechanical properties and performance for resolving environmental and energy-effective water purification. This paper presents an overview of the effects of different hydrophilic nanomaterials, including mineral nanomaterials (e.g., silicon dioxide (SiO2) and zeolite), metals oxide (e.g., copper oxide (CuO), zirconium dioxide (ZrO2), zinc oxide (ZnO), antimony tin oxide (ATO), iron (III) oxide (Fe2O3) and tungsten oxide (WOX)), two-dimensional transition (e.g., MXene), metal-organic framework (MOFs), covalent organic frameworks (COFs) and carbon-based nanomaterials (such as carbon nanotubes and graphene oxide (GO)). The influence of these nanoparticles on the surface and structural changes in the membrane is thoroughly discussed, in addition to the performance efficiency and antifouling resistance of the developed membranes. Recently, GO has shown a considerable capacity in wastewater treatment. This is due to its nanometer-sized holes, ultrathin layer and light and sturdy nature. Therefore, we discuss the effect of the addition of hydrophilic GO in neat form or hyper with other nanoparticles on the properties of different polymeric membranes. A hybrid composite of various NPs has a distinctive style and high-quality products can be designed to allow membrane technology to grow and develop. Hybrid composite NPs could be used on a large scale in the future due to their superior mechanical qualities. A summary and future prospects are offered based on the current discoveries in the field of mixed matrix membranes. This review presents the current progress of mixed matrix membranes, the challenges that affect membrane performance and recent applications for wastewater treatment systems.

Thermal Conductivity Enhancement of Atomic Layer Deposition Surface-Modified Carbon Nanosphere and Carbon Nanopowder Nanofluids.

In this paper, we present a study on thermal conductivity and viscosity of nanofluids containing novel atomic layer deposition surface-modified carbon nanosphere (ALD-CNS) and carbon nanopowder (ALD-CNP) core-shell nanocomposites. The nanocomposites were produced by atomic layer deposition of amorphous TiO2. The nanostructures were characterised by scanning (SEM) and transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, thermogravimetry/differential thermal analysis (TG/DTA) and X-ray powder diffraction (XRD). High-concentration, stable nanofluids were prepared with 1.5, 1.0 and 0.5 vol% nanoparticle content. The thermal conductivity and viscosity of the nanofluids were measured, and their stability was evaluated with Zeta potential measurements. The ALD-CNS enhanced the thermal conductivity of the 1:5 ethanol:water mixture by 4.6% with a 1.5 vol% concentration, and the viscosity increased by 37.5%. The ALD-CNS increased the thermal conductivity of ethylene-glycol by 10.8, whereas the viscosity increased by 15.9%. The use of a surfactant was unnecessary due to the ALD-deposited TiO2 layer.

Rapid Synthesis Method of Ag3PO4 as Reusable Photocatalytically Active Semiconductor.

The widespread use of Ag3PO4 is not surprising when considering its higher photostability compared to other silver-based materials. The present work deals with the facile precipitation method of silver phosphate. The effects of four different phosphate sources (H3PO4, NaH2PO4, Na2HPO4, Na3PO4·12 H2O) and two different initial concentrations (0.1 M and 0.2 M) were investigated. As the basicity of different phosphate sources influences the purity of Ag3PO4, different products were obtained. Using H3PO4 did not lead to the formation of Ag3PO4, while applying NaH2PO4 resulted in Ag3PO4 and a low amount of pyrophosphate. The morphological and structural properties of the obtained samples were studied by X-ray diffractometry, diffuse reflectance spectroscopy, scanning electron microscopy, infrared spectroscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity of the materials and the corresponding reaction kinetics were evaluated by the degradation of methyl orange (MO) under visible light. Their stability was investigated by reusability tests, photoluminescence measurements, and the recharacterization after degradation. The effect of as-deposited Ag nanoparticles was also highlighted on the photostability and the reusability of Ag3PO4. Although the deposited Ag nanoparticles suppressed the formation of holes and reduced the degradation of methyl orange, they did not reduce the performance of the photocatalyst.