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A sustainable low-cost activated carbon substitute was produced based on pretreated lignocellulosic biomass, especially spruce sawdust. A harmful liquid waste, desalination brine, was used for the treatment of a solid wood industry waste, spruce sawdust. This approach is in the circular economy theory and aims at the decarbonization of the economy. Pretreated sawdust was tested as an adsorbent appropriate for the removal of a commonly used pollutant, methylene blue, from industrial wastewater. The adsorption capacity of the pretreated material was found to have increased four times compared to the untreated one in the case that the Freundlich equation was fitted to the isotherms' data, i.e., the one with the best fit to the isotherm's experimental data of the three isotherm models used herein. The treatment experimental conditions with desalination brine that gave maximum adsorption capacity correspond to a 1.97 combined severity factor in logarithmic form value. Moreover, a kinetic experiment was carried out with regard to the methylene blue adsorption process. The desalination brine-pretreated sawdust adsorption capacity increased approximately two times compared to the untreated one, in the case when the second-order kinetic equation was used, which had the best fit of the kinetic data of the three kinetic models used herein. In this case, the pretreatment experimental conditions that gave maximum adsorption capacity correspond to −1.049 combined severity factor in logarithmic form. Industrial scale applications can be based on the kinetic data findings, i.e., spruce sawdust optimal pretreatment conditions at 200 °C, for 25 min, with brine solution containing 98.12 g L−1 NaCl, as they are related to a much shorter adsorption period compared to the isotherm data. [ABSTRACT FROM AUTHOR]

CuFeS2 is a prominent chalcogenide that possesses similar optical properties and a significantly lower cost, compared to gold. Additionally, covalent organic frameworks are a class of materials at the forefront of current research, mainly used as photoactive components and porous absorbers. Hence, in this work, hydrophilic CuFeS2 particles are coupled with multi-functional covalent organic frameworks through ionic bonding to produce a hybrid material with unique and optimized properties. To render the CuFeS2 particles negatively charged and dispersible in water, we coated them with sodium dodecyl sulfonate, shifting the surface plasmon resonance of the nanoparticles from 472 to 492 nm. When they are electrostatically assembled with the positively charged COFs, an S-scheme is formed and the fluorescence of the hybrid materials is highly quenched, with the electron transfer happening from the networks to the nanoparticles and a simultaneous energy exchange which is dependent on the emission wavelength. Through detailed fluorescence spectroscopy, time-resolved measurements and Stern–Volmer analysis, we identified an efficient emission quenching that differs from the bulk to the exfoliated hybrid system, while detailed electron microscopy studies demonstrated the strong interaction between the two components. The quenching mechanisms and the on or off surface resonance dependent lifetime could be applied to photocatalytic and photovoltaic applications. [ABSTRACT FROM AUTHOR]

In this study, 3-dimensional molybdenum disulfide (MoS2) structures, integrated with hematite (α-Fe2O3) nanoparticles, were fabricated under a convenient two-step hydrothermal route. The fabricated photocatalytic nanocomposites consist of well-arranged MoS2 flakes, resembling spherical flower-like morphology, and the nanoparticulate α-Fe2O3 structures decorate the 3D network. By raising the α-Fe2O3 weight ratio, the composites' specific surface area and morphology were not affected, regardless of the partial cover of the cavities for higher hematite content. Moreover, the crystallinity examination with XRD, Raman, and FTIR techniques revealed that the precursor reagents were fully transformed to well-crystalized MoS2 and Fe2O3 composites of high purity, as no organic or inorganic residues could be detected. The photocatalytic oxidation and reduction performance of these composites was evaluated against the tetracycline pharmaceutical and the industrial pollutant hexavalent chromium, respectively. The improvement in the removal efficiencies demonstrates that the superior photoactivity originates from the high crystallinity and homogeneity of the composite, in combination with the enhanced charge carriers' separation in the semiconductors' interface. [ABSTRACT FROM AUTHOR]

The present work focuses on TiO2 modification with carbon dots (CDs) using a hydrothermal process, which results in the synthesis of CD/TiO2 nanocomposite photocatalysts characterized by exceptional optoelectronic properties. The structural and physicochemical properties of the obtained nanocomposites, which contained varying amounts of CDs, were precisely assessed. HR-TEM analysis showed that the prepared nanocomposites consisted of rod-shaped TiO2 nanoparticles and CDs well-dispersed on their surface. The optical properties of the nanocomposites were studied using UV–vis diffuse reflectance spectroscopy. All CD/TiO2 samples presented decreased energy gap values compared with bare TiO2 samples; the band gap was further decreased as the CD concentration rose. Electrochemical measurements revealed that the presence of CDs improved the photocurrent response of the TiO2, presumably due to enhanced charge separation and decreased recombination. The synthesized nanomaterials were used as photocatalysts to produce hydrogen via the photoreforming of ethanol and glycerol green organic compounds, under 1-sun illumination. The photocatalytic experiments confirmed that the optimum loading of CDs corresponded to a percentage of 3% (w/w). Ethanol photoreforming led to a H2 production rate of 1.7 μmol∙min−1, while in the case of the glycerol sacrificial agent, the corresponding rate was determined to be 1.1 μmol∙min−1. The recyclability study revealed that the photocatalyst exhibited consistent stability during its reuse for hydrogen production in the presence of both ethanol and glycerol. [ABSTRACT FROM AUTHOR]

Homojunction engineering has emerged as a potent strategy to evade interfacial stability issues and improve the efficiency of nanostructured metal oxide photocatalysts, though rarely combined with the enhanced light capture ability of three-dimensional macroporous photonic crystal structures. Herein, the formation of nanoscale n-n+ homojunctions between different Mo- and Ca-doped BiVO4 nanocrystals in the skeleton of photonic band gap (PBG) engineered inverse opals is introduced as an advanced approach to simultaneously promote visible light harvesting, electron transport, and charge separation of BiVO4 nanomaterials for the photoelectrocatalytic degradation of pharmaceutical contaminants of emerging concern. Controlled deposition of BiVO4 inverse opal films with tailored PBGs was combined with compositional tuning by Mo- and Ca-doping for slow-photon-assisted visible-light-activated (VLA) photocatalysis. The introduction of shallow dopant states in the Mo-, Ca-doped BiVO4 nanoparticles with relatively weak structural distortions but significantly different donor concentrations resulted in a broad distribution of type-II homojunctions in the nanocrystalline inverse opal walls. Comparative photoelectrochemical evaluation showed that nanostructured homojunction Mo-BiVO4/Ca-BiVO4 photonic films largely outperformed their individual constituents in both photocurrent generation and the VLA photocatalytic degradation rate. Moreover, they exhibited markedly improved performance in the photoelectrocatalytic degradation of tetracycline and ciprofloxacin broad-spectrum antibiotics as well as salicylic acid under visible light, validating their application potential in VLA water remediation by pharmaceutical micropollutants. [ABSTRACT FROM AUTHOR]

Following the long-standing use of the liquid exfoliation of graphite for the production of graphene, a number of analogous van der Waals 2D nanomaterials have been also produced and studied extensively for several applications. Recently, liquid exfoliation has also been applied to isolate non-van der Waals 2D nanostructures. Here, we describe a green procedure for the liquid exfoliation of natural hematite and magnetite – natural iron ores – obtained from the Greek territory. Natural iron ores were exfoliated in a solution of melamine in water under mild sonication. The ultrathin exfoliated nanoplatelets, hematene and magnetene, respectively, form stable dispersions in pure water and have been extensively characterized by spectroscopic and microscopic techniques. Optical limiting experiments reveal the efficiency of the present non-van der Waals 2D nanomaterials, rendering them highly attractive for several applications in opto-electronics and photonics. [ABSTRACT FROM AUTHOR]

The synthesis of titania-based composite materials with anticancer potential under visible-light irradiation is the aim of this study. In specific, titanium dioxide (TiO2) nanoparticles (NPs) chemically modified with silver were embedded in a stimuli-responsive microgel (a crosslinked interpenetrating network (IP) network that was synthesized by poly (N-Isopropylacrylamide) and linear chains of polyacrylic acid sodium salt, forming composite particles. The ultimate goal of this research, and for our future plans, is to develop a drug-delivery system that uses optical fibers that could efficiently photoactivate NPs, targeting cancer cells. The produced Ag-TiO2 NPs, the microgel and the composite materials were characterized through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), micro-Raman spectroscopy, ultraviolet-visible spectroscopy (UV-Vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM). Our results indicated that Ag-TiO2 NPs were successfully embedded within the thermoresponsive microgel. Either Ag-TiO2 NPs or the composite materials exhibited high photocatalytic degradation efficiency on the pollutant rhodamine B and significant anticancer potential under visible-light irradiation. [ABSTRACT FROM AUTHOR]