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Photovoltaic modules are impacted by overheating, which degrades their conversion efficiency and shortens their lifespan. This work attempts to study the cooling potential for a hybrid photovoltaic/thermal (PV/T) system by employing CuO and Fe2O3 nanofluids with 0.2% and 0.3% volume fractions (φ), circulated in a heat exchanger attached at the rear side of the PV module to lower the temperature of the PV cells and improve its energy and exergy efficiencies. Consequently, a 2D numerical model was analysed given the energy balance across the PV/T system layers, which is evaluated in line with measured experimental data. The results indicate that the successfully synthesised nanomaterials could improve the performance of the nanofluids and increase the heat exchange between PV/T system layers, reducing the PV cells’ temperature by 23.49% and 34.58% when cooling by CuO and Fe2O3 nanofluids at φ=0.3%. Compared to the uncooled PV module, the electrical efficiency has increased by 9.21% and 10.30%, while thermal efficiency increased by 38.9% and 43.3% under cooling with CuO and Fe2O3 nanofluids, respectively. Thereby, the exergy destruction (exergy losses) and entropy generation have decreased by about 26% and 68% when cooling with Fe2O3 nanofluid, which improved the exergy efficiency by 13% more than CuO nanofluid.

Antifouling membranes were developed by encapsulating amino-functionalized nano-silica in polymeric mixes of polyethersulfone (PES) and polyvinyl pyrrolidone (PVP). Subsequently, the membranes were modified with a nano-Ag/PVP coating layer. The membranes’ performance was assessed against synthetic whey solutions model to mimic dairy wastewater. Various techniques were harnessed to evaluate the membranes' composition, structure and morphology, including SEM, XPS, XRD, AFM, mechanical characteristics, porosities and contact angles. Findings indicated that nanocomposite made with 1.5 % amino-functionalized nano-silica (M3) revealed optimum performance and was capable to separate 90 % of the whey in the feed along with a permeate flux of 238 L/m2.h, when the feed whey concentration was 0.4°Brix. the equivalent membrane but coated with a nano-Ag /PVP layer (M3S) displayed a trivial drop in permeate flux (229.3 L/m2.h) comparing to uncoated one. Nonetheless, the addition of the coating boosted the separation efficiency up to 99.7 % of the whey in the feed. The fouling test indicated that the coated membrane (M3S) had superior antifouling property, where flux recovery ratio (FRR) hit 99.5 % with a diminution in the backwash rate.

Abstract 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.

Recently, photovoltaic technology applications have occupied a wide range in electric generation. The temperature rising higher than the operating temperature permissible is the weak point facing this technology, which significantly influences the performance of the photovoltaic cells. Using nanofluids as the coolant of photovoltaic (PV) modules is an effective method, circulating nanofluids in the heat exchanger attached to the backside of the PV module to absorb excess heat and enhance the performance of the PV module. The current work investigates using zirconium oxide (ZrO 2) nanofluid as a coolant at different volume concentrations (0.015 vol%, 0.025 vol%, 0.0275 vol%) in deionized (DI) water to reduce the temperature of the photovoltaic PV cells and then analyses the performance from the energy/exergy viewpoints. The results indicate that the PV module temperature was reduced by 10.2 °C when cooled by ZrO 2 nanofluid at 0.0275% volume concentration in DI water compared to the reference PV module, resulting in remarkable system energy and exergy enhancement. Besides, the cooling by DI water has decreased the PV module temperature by 5.1 °C. The overall efficiencies gradually increment with an increase in volume concentration by 8.9%, 18.8 % and 24.4%, respectively, compared with PV modules cooled by DI water. Using ZrO 2 nanofluids with 0.0275 vol% could enhance the exergy efficiency by 66.8% and reduce the exergy losses and entropy generation by 7% and 26%, respectively.

In order to address the limitation of low flux in ultrafiltration (UF), a suitable additive is introduced into the base polymer to modify the membrane morphology, thereby enhancing flux rates. In this study, chamomile leaf nanoparticles (Chm NPs) were investigated as a novel green material for utilizing in UF membrane synthesizes. To enhance comprehension of the influence of Chm on the synthesis of PES UF membranes, a series of membranes were fabricated by including different quantities of Chm into the casting solution; (0, 0.5, 1.5, and 2 wt. %.). The synthesized membranes were fully characterized, through the porosity, pore size, hydrophilicity, membrane morphology, and UF efficiency. Manufactured PES/Chm membranes demonstrated significantly increased permeate water flux (PWF) (up to 498 kg/m2 h), which was four times that of the pristine PES membrane (116 kg/m2 h), besides that the bovine serum albumin (BSA) and Congo red dye (CR) rejection of PES/Chm membranes was still kept high. The enhanced PWF was mostly due to the more porous membrane structure and increased hydrophilicity. Meanwhile, the higher surface hydrophilicity of the PES/Chm membranes resulted in greater antifouling performance and the high flux recovery ratio (FRR) of 93 %. Based on the results of this research, the Chm may be used as a novel green additive with substantial application potential in the fabrication of UF membranes wastewater treatment.

This study aims to optimize operating parameters of the effect of embedded silica nanoparticles (SiO2 NPs) and modified silica NPs with polyethylenimine (PEI) (SiO2-g-PEI NPs) into polyethersulfone (PES) to fabricate a mixed matrix membranes (MMMs) for pharmaceutical wastewater treatment. The performance of modified MMMs was compared in the separation of Mebeverine hydrochloride (MBV) from aqueous pharmaceutical wastewater. In order to produce a particular quantity of flux and rejection above desired levels, an optimization technique was used to find the best values for various important process parameters. To enhance the effectiveness on a bigger scale, response surface methodology (RSM) and analysis of variance (ANOVA) were utilized as mathematical and statistical approaches. This study examined the effects of operational parameters on the PES-NPs membranes permeate flux and MBV rejection for each sample. These parameters included SiO2/or SiO2-g-PEI NPs content (0.7–1 wt %), solution feed pH values (4-10), and MBV concentration (10–100 ppm). A mathematical model to calculate the permeate flux and rejection (%) was established. The results showed that the SiO2 MMMs had the best performance of 38.27 LMH permeate flux and 81.26% of MBV rejection, while the permeate flux and MBV rejection % for SiO2-g-PEI MMMs were 104.11LMH and 99.00%. The SiO2 wt % of 0.8447%, MBV concentration of 98.18 ppm, and pH of 4 were the optimal parameters for the SiO2 MMMs, while the optimal parameters for SiO2-g-PEI MMMs were SiO2-g-PEI wt. % of 0.93%, MBV concentration of 22.7 ppm, and pH of 4.79 for eliciting the optimum response.

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%.

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.

Overheating of photovoltaic (PV) cell is one of the most common issues that cause the degradation of their function and reduce conversion efficiency. This work investigates the effect of using a novel TiO2-CuO hybrid nanofluid to improve the energy and exergy of photovoltaic thermal (PVT) systems by reducing PV cell temperature. Serpentine tubes soldered on an absorbing plate attached behind the PV module were proposed to improve heat removal of the PV module with volume concentrations of 0.2 vol% and 0.3 vol%, with a flow rate of 1.16 L/min. Improving the thermophysical properties of the hybrid nanofluid has reduced the temperature of the PV module by 39% more than the uncooled PV module. The PVT system's electrical power and overall efficiency improved by 77.5% and 58.2%, respectively, at increased volume concentration to 0.3 vol% compared with the uncooled PV module. The exergy analysis indicated an increase in the overall exergy efficiency by 14.97 %, with thermal exergy dropping because of the closer the outlet nanofluid temperature to ambient temperature. Hybrid nanofluid cooling has improved exergy efficiency to 14.97%, reducing exergy losses by 37.9% and entropy generation by 69.6% at 0.3 vol%. The economic analysis shows a better payback period of 21 months when cooling with a hybrid nanofluid compared with the uncooled PV module.

Development and application of hybrid membranes containing multi-component materials are increasing day by day in the fields of environmental protection and water treatment. In this research, the efficiency of titania nanowire (TiO2 NW)-based self-supported hybrid membranes was investigated in the removal of Escherichia coli (E. coli) bacteria and MS2 bacteriophages from contaminated water mimicking the microorganism suspension. Furthermore, toxicology tests on the as-prepared membranes were also performed. TiO2 NWs were coated with iron(III) oxide (Fe2O3) and copper(II) oxide (CuO) nanoparticles, respectively, and cellulose was used as reinforcement material. It was found that, the functionalisation strongly affected the MS2 removal ability of as-prepared membranes, which can be due to the electrostatic interactions between the surface of hybrid membrane and the bacteriophages. The most efficient removal (greater than or equal to 99.99%) was obtained with the TiO2 NW-CuO-cellulose membrane at pH 7.0. The fabricated hybrid membranes were characterized by micro computed tomography (μCT), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), contact angle measurement and inductively coupled optical emission spectrometry (ICP-OES) techniques. This study shows a simple route of the usage of novel and effective inorganic nanowire-based hybrid membranes for bacteria and virus removal, providing new pathways in the field of water filtration technologies.

The temperature rising of the photovoltaic (PV) modules is a major issue leading to a reduction in their conversion efficiency and low output power. Therefore, removing heat from the PV module is necessary to permanently work and improve the electrical power output. Serpentine pipes and a thermal absorber plate has proposed with fluid circulation to reduce the PV cell temperature and improve their efficiency. The current work experimentally investigates the effect of using tungsten trioxide (WO3) nanofluids on the PVT system's energy and exergy efficiency at different volume concentrations of 0. 5 vol%, 0. 75 vol%, and 1 vol%. The results indicated an increment in the electrical power output by 11.15 W due to reducing the PV temperature by 21.4% and enhancing the PVT overall efficiency by 29.6% compared with the cooling by Deionized (DI) water. Increasing the volume concentration of nanoparticles increased the Reynolds number, and the Nusselt number enhanced the heat transfer coefficient and increased the pressure drop. Improving the thermal properties of the nanofluid has increased the electrical exergy efficiency and lowered the thermal exergy efficiency due to the reduction in thermal exergy quality. Compared to DI water cooling, exergy losses and entropy generation were reduced by 10% and 34.8%, respectively.

In this study, Zr-pillared montmorillonite clays (Zr-PILCs) were synthesized using two different precursor materials: raw montmorillonite (CM) and sodium ion-saturated montmorillonite (Na-CM) at different Zr/clay ratios (2.5, 5 and 10 mmol/g). To study the effect of Zr concentration and clay pre-treatment with NaCl on pillaring, the modified clay samples were characterized in detail using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy (STEM-EDX). The XRD analysis showed the increase of basal spacing of Zr-PILCs prepared from both precursor materials: from 1.26 to 1.74 nm in the case of CM, and from 1.13 to 1.93 nm for Na-CM. Results from FT-IR revealed new bands ascribed to Zr-O bonds in the range of 400–500 cm−1 in Zr-pillared samples obtained from Na-CM at Zr/clay ratios of 2.5 and 5 mmol/g. The distribution and nature of Zr species in between the silicate layers were studied using STEM-EDX and HAADF imaging. They were found to be separated by a distance of 1.5–3 nm and their thickness lies in the range of 1–2 nm. Pillared clays prepared from pre-treatment with NaCl were more thermally stable at higher temperatures.

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.

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.

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.

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.

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.

The novel photoactive membranes have grabbed the attention in the field of environmental protection by employing wastewater treatments and the removal of microorganisms or organic pollutants from wastewater. Here we present a promising self-supported photoactive hybrid membrane for future antimicrobial and water treatment applications. In this study, the efficiency of bacterial cellulose (BC) - zinc oxide (ZnO) - multi walled carbon nanotube (MWCNT) hybrid membranes in the adsorption and photocatalytic degradation of methylene blue (MB) under UV radiation and the removal of Escherichia coli (E. coli) was investigated. It was found that the photocatalytic efficiency is strongly dependent on both the preparation method and the amount of ZnO-MWCNT additives loaded into the hybrid membranes. The characterization of BC-ZnO-MWCNT membranes was done using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and X-ray micro computed tomography (μCT) to study the morphological and porosity aspect of the prepared-membranes. The promising results of this study could provide a new pathway in the field of photocatalysed-based water treatment technology by the application of hybrid membranes.

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.

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.

ZnO photocatalysts were synthesized via solvothermal method and a reduced experimental design (Box–Behnken) was applied to investigate the influence of four parameters (temperature, duration, composition of the reaction mixture) upon the photocatalytic activity and the crystal structure of ZnO. The four parameters were correlated with photocatalytic degradation of methyl orange and the ratio of two crystallographic facets ((002) and (100)) using a quadratic model. The quadratic model shows good fit for both responses. The optimization experimental results validated the models. The ratio of the crystal facets shows similar variation as the photocatalytic activity of the samples. The water content of the solvent is the primary factor, which predominantly influence both responses. An explanation was proposed for the effect of the parameters and how the ratio of (002) and (100) crystal facets is influenced and its relation to the photocatalytic activity. The present research laconically describes a case study for an original experimental work, in order to serve as guideline to deal with such complicated subjects as quantifying influence of synthesis parameters upon the catalytic activity of the obtained ZnO.

In the present work, ternary composites were synthesized from commercial titanias (Evonik Aeroxide P25, Aldrich anatase—AA and Aldrich rutile—AR) and two noble metals (gold and platinum). This research focuses on the composition of the photocatalysts, especially on the noble metals. The ratio between the noble metals varies from 0.25 to 0.75% in each composite for each noble metal. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS) measurements were carried out to investigate the structural and optical properties. From the TEM, it can be observed that the particle sizes of the noble metals were between 1 and 4 nm, while the (anatase and rutile) crystals of P25 were 20–40 nm. The XRD showed that the semiconductors’ composition remained unchanged during/after the deposition of noble metal nanoparticles. By the DRS measurements, using the Kubelka–Munk equation, it can be concluded that the deposition of the noble metal nanoparticles resulted the decrease of the bandgap energies of the titanias. The photocatalytic activity was investigated under the irradiation of UV light. Oxalic acid and salicylic acid were used as model pollutants. The hydrogen production capacity was investigated as well, where the sacrificial agent was oxalic acid, and UV irradiation was used.

A comparative research on stability, viscosity (µ), and thermal conductivity (k) of carbon nanosphere (CNS) and carbon nanopowder (CNP) nanofluids was performed. CNS was synthesized by the hydrothermal method, while CNP was provided by the manufacturer. Stable nanofluids at high concentrations 0.5, 1.0, and 1.5 vol% were prepared successfully. The properties of CNS and CNP nanoparticles were analyzed with Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), specific surface area (SBET), X-ray powder diffraction (XRD), thermogravimetry/differential thermal analysis (TG/DTA), and energy dispersive X-ray analysis (EDX). The CNP nanofluids have the highest k enhancement of 10.61% for 1.5 vol% concentration compared to the base fluid, while the CNS does not make the thermal conductivity of nanofluids (knf) significantly higher. The studied nanofluids were Newtonian. The relative µ of CNS and CNP nanofluids was 1.04 and 1.07 at 0.5 vol% concentration and 30 °C. These results can be explained by the different sizes and crystallinity of the used nanoparticles.

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.

In the present work, visible light active bismuth oxyiodide (BiOI) was immobilized on a commercial, non-conductive support (an Al2O3 based ceramic paper) using a novel two-step spray coating technique and investigated with different characterization methods (e.g., SEM, Raman, XPS). Our main goal was to eliminate the separation costs after the photocatalytic measurement and investigate the chemical relevance and opportunity to use this technique in the industry. Our as-prepared uniform BiOI layer had similar properties to the well-known reference BiOI powder. The Raman and XPS measurements confirmed that the enriched amount of the surface iodine defined the color and as well the band gap of the BiOI layer. The durable BiOI layers have prominent photocatalytic activity under UV and visible light irradiation as well. The scale-up procedure proved that the designed BiOI coated paper was reusable and potentially applicable in the industry by straightforward scale-up, which is due to the elaborated non-conventional BiOI coverage estimation method. This immobilization technique could open several opportunities for immobilizing many other visible light active photocatalysts with simple materials and low cost.

For better electrical contacts of potential devices, growth of vertically aligned carbon nanotubes (CNT forests) directly onto conductive substrates is an emerging challenge. Here, we report a systematic study on the CCVD synthesis of carbon nanotube forests on titanium based substrates. As a crucial issue, the effect of the presence of an insulating layer (alumina) on the growing forest was investigated. Other important parameters, such as the influence of water vapor or the Fe-Co catalyst ratio, were also studied during the synthesis. As-prepared CNT forests were characterized by various techniques: scanning and transmission electron microscopies, Raman spectroscopy, spectroscopic ellipsometry. CNT forests grown directly onto the conductive substrate were also tested as electrodes in hybrid halide perovskite photodetectors and found to be effective in detecting light of intensity as low as 3 nW.

This article reviews recent results in the field of nanotube research obtained at EPFL. We show in particular that with catalytic deposition techniques such as chemical vapor deposition carbon nanotubes with controlled properties can be obtained. We then discuss the functionalization of these CVD-grown nanotubes for the realization of fibers and composites, as well as their use in field emission devices.