Synthesis of 2D Germanane (GeH): a New, Fast, and Facile Approach.

Germanane (GeH), a germanium analogue of graphane, has recently attracted considerable interest because its remarkable combination of properties makes it an extremely suitable candidate to be used as 2D material for field effect devices, photovoltaics, and photocatalysis. Up to now, the synthesis of GeH has been conducted by substituting Ca by H in a ß-CaGe2 layered Zintl phase through topochemical deintercalation in aqueous HCl. This reaction is generally slow and takes place over 6 to 14 days. The new and facile protocol presented here allows to synthesize GeH at room temperature in a significantly shorter time (a few minutes), which renders this method highly attractive for technological applications. The GeH produced with this method is highly pure and has a band gap (Eg ) close to 1.4 eV, a lower value than that reported for germanane synthesized using HCl, which is promising for incorporation of GeH in solar cells.

Super porous TiO2 photocatalyst: Tailoring the agglomerate porosity into robust structural mesoporosity with enhanced surface area for efficient remediation of azo dye polluted waste water.

The low surface area of TiO2 (50 m2g-1 - Degussa P25) due to randomly oriented, agglomerated nanostructures and charge carrier recombination tendency, has till date been its major limitation for photocatalytic remediation of polluted wastewater. This study presents an innovative process to design super porous TiO2 nanostructures with high effective surface area (238 m2g-1), robust, structurally ordered mesoporosity via a simple sol-gel assisted reflux method. Detailed material characterization studies suggest that the higher degree of intermolecular ligation in novel templates such as butanetetracarboxylic or tricarballylic acid modified titanium hydroxide gels resulted in retainment of the porous structure during the urea assisted combustion synthesis. The induction of robust structural porosity is accompanied by a reduction in pore size distribution, an increase in pore volume leading to significantly higher total surface area of the synthesized TiO2. Detailed investigation of dye adsorption kinetics and photocatalytic degradation kinetics, complemented by kinetic modeling analysis confirmed that the super porous TiO2 with robust mesoporous structure outperforms the rest of synthesized TiO2 catalyst (having only agglomerate porosity) in terms of its superior adsorption capacity, faster diffusion kinetics and photocatalytic activity for degradation of Amaranth dye. Thus, the super porous TiO2 shows promising potential for application in sustainable photocatalytic technology for remediation of wastewater contaminated with azo dyes.

The Role of Titanium Dioxide on the Hydration of Portland Cement: A Combined NMR and Ultrasonic Study.

Titanium dioxide (TiO2) is an excellent photocatalytic material that imparts biocidal, self-cleaning and smog-abating functionalities when added to cement-based materials. The presence of TiO2 influences the hydration process of cement and the development of its internal structure. In this article, the hydration process and development of a pore network of cement pastes containing different ratios of TiO2 were studied using two noninvasive techniques (ultrasonic and NMR). Ultrasonic results show that the addition of TiO2 enhances the mechanical properties of cement paste during early-age hydration, while an opposite behavior is observed at later hydration stages. Calorimetry and NMR spin-lattice relaxation time T1 results indicated an enhancement of the early hydration reaction. Two pore size distributions were identified to evolve separately from each other during hydration: small gel pores exhibiting short T1 values and large capillary pores with long T1 values. During early hydration times, TiO2 is shown to accelerate the formation of cement gel and reduce capillary porosity. At late hydration times, TiO2 appears to hamper hydration, presumably by hindering the transfer of water molecules to access unhydrated cement grains. The percolation thresholds were calculated from both NMR and ultrasonic data with a good agreement between both results.

Steam-Induced Coarsening of Single-Unit-Cell MFI Zeolite Nanosheets and Its Effect on External Surface Brønsted Acid Catalysis.

Commonly used methods to assess crystallinity, micro-/mesoporosity, Brønsted acid site density and distribution (in micro- vs. mesopores), and catalytic activity suggest nearly invariant structure and function for aluminosilicate zeolite MFI two-dimensional nanosheets before and after superheated steam treatment. Yet, pronounced reaction rate decrease for benzyl alcohol alkylation with mesitylene, a reaction that cannot take place in the zeolite micropores, is observed. Transmission electron microscopy images reveal pronounced changes in nanosheet thickness, aspect ratio and roughness indicating that nanosheet coarsening and the associated changes in the external (mesoporous) surface structure are responsible for the changes in the external surface catalytic activity. Superheated steam treatment of hierarchical zeolites can be used to alter nanosheet morphology and regulate external surface catalytic activity while preserving micro- and mesoporosity, and micropore reaction rates.

Cytotoxicity of prion protein-derived cell-penetrating peptides is modulated by pH but independent of amyloid formation.

Prion diseases are associated with conversion of cellular prion protein (PrPC) into an abnormally folded and infectious scrapie isoform (PrPSc). We previously showed that peptides derived from the unprocessed N-termini of mouse and bovine prion proteins, mPrP1-28 and bPrP1-30, function as cell-penetrating peptides (CPPs), and destabilize model membrane systems, which could explain the infectivity and toxicity of prion diseases. However, subsequent studies revealed that treatment with mPrP1-28 or bPrP1-30 significantly reduce PrPSc levels in prion-infected cells. To explain these seemingly contradictory results, we correlated the aggregation, membrane perturbation and cytotoxicity of the peptides with their cellular uptake and intracellular localization. Although the peptides have a similar primary sequence, mPrP1-28 is amyloidogenic, whereas bPrP1-30 forms smaller oligomeric or non-fibrillar aggregates. Surprisingly, bPrP1-30 induces much higher cytotoxicity than mPrP1-28, indicating that amyloid formation and toxicity are independent. The toxicity is correlated with prolonged residence at the plasma membrane and membrane perturbation. Both ordered aggregation and toxicity of the peptides are inhibited by low pH. Under non-toxic conditions, the peptides are internalized by lipid-raft dependent macropinocytosis and localize to acidic lysosomal compartments. Our results shed light on the antiprion mechanism of the prion protein-derived CPPs and identify a potential site for PrPSc formation.

Dependence of surface aging on DNA topography investigated in attractive bimodal atomic force microscopy.

Here we employ bimodal atomic force microscopy (AFM) to investigate the relevance of the aging of the surface and accumulation of adsorbates on the resolved topography of biomolecules. We produce raw bimodal images and a set of contrast channels derived from these to show that the imaging of DNA molecules on hydrophilic model substrates such as mica should be performed immediately after the sample is prepared. Days after preparation, i.e. 48 hours, the adsorbates shield the forces arising from the true substrate and molecule and the molecule might become "invisible" in the images. We employ dsDNA molecules on mica as a model system since the nominal height of dsDNA is comparable to the height of the adsorbed films. With this set up, the molecules can fully disappear under attractive imaging due to the shielding effects of the adsorbates. We further transform the images obtained immediately after cleaving the mica surface and show that the data are then suitable to be transformed into more physically meaningful maps such as Hamaker maps.

Surface alteration of calcite: interpreting macroscopic observations by means of AFM.

Wettability has been recognized to play a fundamental role in the efficacy of water flooding processes of carbonate oil and gas reservoirs. However, the theoretical mechanism governing this process is still not entirely understood. This can be partly attributed to the absence of ad hoc tools and standardized sample-preparation methodologies for comprehensive transient characterization of the mineral surface. Here, we use atomic force microscopy (AFM) to investigate the effect of different calcite sample-preparation methodologies in estimating the macroscopic water static contact angle (SCA). Single crystal calcite surfaces are aged in deionized (DI) water baths, for different exposure times, and dried by different techniques, to reveal SCA discrepancies. Trends and observations are explained with the use of time-dependent adhesion maps of the surface obtained by bimodal AFM. In this context, the AFM interpretation of macroscopic observations provides a means to single out the different factors influencing wettability, thus allowing for a more standardized description of the processes responsible for the modification of the affinity between the mineral rock and injected water.

Graphene foam developed with a novel two-step technique for low and high strains and pressure-sensing applications.

Freestanding, mechanically stable, and highly electrically conductive graphene foam (GF) is formed with a two-step facile, adaptable, and scalable technique. This work also demonstrates the formation of graphene foam with tunable densities and its use as strain/pressure sensor for both high and low strains and pressures.

Self-Pillared, Single-Unit-Cell Sn-MFI Zeolite Nanosheets and Their Use for Glucose and Lactose Isomerization.

Single-unit-cell Sn-MFI, with the detectable Sn uniformly distributed and exclusively located at framework sites, is reported for the first time. The direct, single-step, synthesis is based on repetitive branching caused by rotational intergrowths of single-unit-cell lamellae. The self-pillared, meso- and microporous zeolite is an active and selective catalyst for sugar isomerization. High yields for the conversion of glucose into fructose and lactose to lactulose are demonstrated.

Electron transfer and energy exchange between a covalent organic framework and CuFeS2 nanoparticles.

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.

Graphene arrested in laponite-water colloidal glass.

Graphene production in water from graphite sources is an important technological route toward harvesting the unique properties of this material. Graphene forms thermodynamically unstable dispersions in water, limiting the use of this solvent due to aggregation. We show that graphene-water dispersions can be controlled kinetically to produce graphene by using laponite clay. Laponite exhibits rapid gelation kinetics when dispersed in water above its gelation concentration, allowing graphene aggregation to be halted after exfoliation in water at ambient conditions. The transparency of laponite colloidal glass and films is important in examining the extent of graphene exfoliation.

Capturing water vapors from atmospheric air using superporous gels.

Dehumidification performance of most polymer desiccant materials is unsatisfactory because of the complex adsorption mechanism on polymer surface and non-porous structure. A viable alternative of solid desiccants, especially existing polymer desiccants, for capturing water vapors from moist air is the super-porous gels (SPGs). The presence of interconnected channels of pores in its structure facilitates the transfer of water molecules to the internal structure of SPGs. Therefore, in this research work, we are proposing N-isopropylacrylamide (NIPAM) and acrylamide (AM) based thermoresponsive SPGs as a potential alternative to the existing conventional solid desiccants. To ensure the formation of interconnected capillary channels, the SPGs were synthesized via gas blowing and foaming technique. Surface morphology of the SPGs was studied using scanning electron microscopy (SEM) and the other physio-chemical characteristics were studied using different techniques like fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). Water vapors adsorption properties of the SPGs were explored via adsorption isotherm and kinetics. The adsorption isotherm was found to be of type-III isotherm with a maximum adsorption capacity of 0.75 gw/gads at 25 °C and 90% relative humidity. Experimental isotherm data correlated well with BET, FHH and GAB isotherm models. Adsorption kinetics suggested that the water vapors diffusion followed intraparticle diffusion and liquid field driving mechanisms collectively. SPGs exhibited very good regeneration and reusability for ten continuous adsorption/desorption cycles. Therefore, the dehumidification efficiency of synthesized SPGs shows that they have potential to replace most of the conventional solid desiccant materials in use.

Surface properties of alkylsilane treated date palm fiber.

The present work focuses on investigating the effect of non-fluoro short-chain alkylsilane treatment on the surface characteristic of date palm (Phoenix dactylifera) fiber. Raw date palm fiber (DPF) was treated with octylsilane and the surface properties of treated fiber was investigated using thermogravimetric analysis (TGA), fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), contact angle analysis and X-ray diffraction (XRD) on configuring the thermal stability, chemical structures and surface properties (morphology, hydrophobicity and crystallinity). The decomposition temperature of 75% mass loss raw and treated DPF, the onset of temperatures were increased from 464 to 560 °C with the introduction of alkylsilane. Hydrophobicity and crystallinity index of the DPF fibers were increased from 66.8° to 116° and 31 to 41, introducing octylsilane to raw DPF. The SEM and XRD experimental results showed that the octylsilane treatment could effectively increase the pore size and crystallinity index as an indication of the removal of non-crystalline cellulosic materials from DPFs. Thermal stability, hydrophobicity and crystallinity of the fibers increased on DFP after alkylsilane treatment. The results indicated that alkylsilane-treated DPFs were a suitable reinforcing substitute for hydrophobic polymer composite.

Advances in the role of natural gums-based hydrogels in water purification, desalination and atmospheric-water harvesting.

Freshwater scarcity is one of the world's foremost environmental stress concerns. In the last few years, with sustainable industrial growth and rapidly growing population, the problem of freshwater shortage has encouraged researchers to conduct comprehensive research for the development of advanced water harvesting and wastewater treatment techniques. Natural gums-based hydrogels have been widely used in different water purification and harvesting applications because of their environment friendly nature, high water absorption, adsorption and retention capacities. In this article, we presented an entirely conceptual and critical review of literature mainly focused on the potential of different natural gums-based hydrogel in water harvesting and wastewater treatment applications. First, different categories of natural gums-based hydrogels including stimuli responsive hydrogels, physically and chemically crosslinked hydrogels, were introduced. Then, the emphasis was given on the role of natural gums-based hydrogels in different wastewater treatment applications like adsorption, photocatalysis and flocculation. After that, the latest research progress on the use of natural gums-based hydrogels in atmospheric water harvesting and seawater desalination was discussed. Finally, different challenges and main limitations associated with the use of natural gums-hydrogels in water purification and harvesting applications were discussed to understand the research gaps and drawbacks which need improvements.

Biobased Castor Oil-Based Polyurethane Foams Grafted with Octadecylsilane-Modified Diatomite for Use as Eco-Friendly and Low-Cost Sorbents for Crude Oil Clean-Up Applications.

Herein we report the synthesis and characterization of novel castor oil-based polyurethane (PU) foam functionalized with octadecyltrichlorosilane (C18)-modified diatomaceous earth (DE) particles, exhibiting superior hydrophobicity and oil adsorption, and poor water absorption, for use in effective clean-up of crude oil spillage in water bodies. High-performance and low-cost sorbents have a tremendous attraction in oil spill clean-up applications. Recent studies have focused on the use of castor oil as a significant polyol that can be used as a biodegradable and eco-friendly raw material for the synthesis of PU. However, biobased in-house synthesis of foam modified with C18-DE particles has not yet been reported. This study involves the synthesis of PU using castor oil, further modification of castor oil-based PU using C18 silane, characterization studies and elucidation of oil adsorption capacity. The FTIR analysis confirmed the fusion of C18 silane particles inside the PU skeleton by adding the new functional group, and the XRD study signified the inclusion of crystalline peaks in amorphous pristine PU foam owing to the silane cross-link structure. Thermogravimetric analysis indicated improvement in thermal stability and high residual content after chemical modification with alkyl chain moieties. The SEM and EDX analyses showed the surface's roughness and the incorporation of inorganic and organic elements into pristine PU foam. The contact angle analysis showed increased hydrophobicity of the modified PU foams treated with C18-DE particles. The oil absorption studies showed that the C18-DE-modified PU foam, in comparison with the unmodified one, exhibited a 2.91-fold increase in the oil adsorption capacity and a 3.44-fold decrease in the water absorbing nature. From these studies, it is understood that this novel foam can be considered as a potential candidate for cleaning up oil spillage on water bodies.

LAPONITE® nanodisk-"decorated" Fe3O4 nanoparticles: a biocompatible nano-hybrid with ultrafast magnetic hyperthermia and MRI contrast agent ability.

Magnetic Fe3O4 nanoparticles "decorated" by LAPONITE® nanodisks have been materialized utilizing the Schikorr reaction following a facile approach and tested as mediators of heat for localized magnetic hyperthermia (MH) and as magnetic resonance imaging (MRI) agents. The synthetic protocol involves the interaction between two layered inorganic compounds, ferrous hydroxide, Fe(OH)2, and the synthetic smectite LAPONITE® clay Na0.7+[(Si8Mg5.5Li0.3)O20(OH)4]0.7-, towards the formation of superparamagnetic Fe3O4 nanoparticles, which are well decorated by the diamagnetic clay nanodisks. The latter imparts high negative ζ-potential values (up to -34.1 mV) to the particles, which provide stability against flocculation and precipitation, resulting in stable water dispersions. The obtained LAPONITE®-"decorated" Fe3O4 nanohybrids were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectroscopy, dynamic light scattering (DLS) and vibrating sample magnetometry (VSM) at room temperature, revealing superior magnetic hyperthermia performance with specific absorption rate (SAR) values reaching 540 W gFe-1 (28 kA m-1, 150 kHz) for the hybrid material with a magnetic loading of 50 wt% Fe3O4/LAPONITE®. Toxicity studies were also performed with human glioblastoma (GBM) cells and human foreskin fibroblasts (HFF), which show negligible to no toxicity. Furthermore, T2-weighted MR imaging of rodent brain shows that the LAPONITE®-"decorated" Fe3O4 nanohybrids predominantly affected the transverse T2 relaxation time of tissue water, which resulted in a signal drop on the MRI T2-weighted imaging, allowing for imaging of the magnetic nanoparticles.

GO crosslinked hydrogel nanocomposites of chitosan/carboxymethyl cellulose - A versatile adsorbent for the treatment of dyes contaminated wastewater.

Graphene oxide (GO) crosslinked nanocomposites hydrogels (NCH) of chitosan (CS) and carboxymethyl cellulose (CMC) were synthesized and the feasibility of its application as a versatile adsorbent for the remediation of cationic (methylene blue, MB) as well as anionic (methyl orange, MO) dyes contaminated wastewater was explored. Initially, GO was functionalized with vinyltriethoxysilane which was subsequently used as a chemical crosslinker to synthesize the NCH of CS and CMC (CS/CMC-NCH) with the polymeric mixture of diallyldimethylammonium chloride and 2-acrylamido-2-methyl-1-propanesulfonic acid. About 99% dye was adsorbed from 50 mg/L dye solution of MB dye with 0.4 g/L of CS/CMC-NCH at pH 7, whereas, for MO about 82% dye was adsorbed with 0.6 g/L of CS/CMC-NCH at pH 3. The Adsorption of both dyes is well explained using pseudo-second-order and Langmuir models with the maximum adsorption capacities of 655.98 mgdye/gads for MB and 404.52 mgdye/gads for MO. Thermodynamics studies suggested spontaneous and exothermic nature of the adsorption process with values of ΔS < 0 and ΔH > 0. Furthermore, CS/CMC-NCH showed excellent regeneration capacity for continuous twenty cycles of adsorption-desorption. Therefore, the synthesized CS/CMC-NCH is a versatile adsorbent that can treat both anionic and cationic dyes contaminated wastewater.

Influence of electrolyte and polymer loadings on mechanical properties of clay aerogels.

The effects of electrolyte and polymer loadings on formation, density, and mechanical properties of clay aerogels have been investigated. Coherent aerogels were formed at all tested concentrations except at a combination of low electrolyte (<0.04 M) and polymer (<1% w/v) concentrations because of partial clay flocculation. The compressive modulus and yield strength of the aerogels containing poly(vinyl alcohol) are sensitive to electrolyte loading at low polymer concentration but are otherwise insensitive. Mechanical properties show power law dependence on aerogel density, which depends mainly on polymer loading. The power law exponent for the compressive modulus is 3.74 when the relative density is used in the model and 5.7 when the measured bulk density is used instead. These high exponent values are attributed to the layered microstructure of these aerogels.

Utilization of gum xanthan based superporous hydrogels for the effective removal of methyl violet from aqueous solution.

In this research work the superporous hydrogels (SPHs) of acrylic acid (AA) and acrylamide (AM) with gum xanthan (GX) were synthesized using glass blowing and foaming technique and tested the feasibility of synthesized SPHs to remove removal of methyl violet dye (MV) by the process of adsorption from aqueous solution. Swelling properties of synthesized SPHs with different concentrations of GX were studied in deionized water and the swelling kinetics followed first-order model. The adsorption of MV using SPHs was highly influenced by the solution pH. Adsorption kinetics followed non-linear pseudo-second-order rate equation, whereas, isotherm of adsorption followed monolayer Langmuir model. Diffusion mechanism of dye molecules was controlled by the combination of two mechanisms i.e. intraparticle and liquid film diffusion mechanisms. Furthermore, during desorption studies, SPHs were efficiently used for the five continuous adsorption-desorption cycles. Hence, the removal of cationic dyes could be done using SPHs of GX as effective adsorbents.

Template-Free, Solid-State Synthesis of Hierarchically Macroporous S-Doped TiO2 Nano-Photocatalysts for Efficient Water Remediation.

Nanosized sulfur-doped titanium dioxide emerged as an attractive photocatalyst in various environmental remediation applications, yet most synthesis methods require hazardous sulfurizing agents and intricate synthesis procedures. Herein, we present a facile, sustainable, and environmentally friendly preparation process for the production of visible-light-active meso-macroporous sulfur-doped anatase TiO2 (S-TiO2) nanoparticles for the first time. This strategy encompasses solventless mixing of titanium salt and surfeit yet nontoxic abundant elemental sulfur under continuous ball milling and moderate thermoannealing. The characterizations of as-obtained S-TiO2 nanoparticles showed enhanced physicochemical properties including distinctive surface features composed of hierarchical hollow macroporous channels having nanostructured mesoporous core walls. The annealing temperature was observed to control the structure and extent of sulfur doping in TiO2. Upon insertion of a sulfur atom into the TiO2 lattice, the band gap energy of S-TiO2 was significantly lowered, facilitating the enhanced photochemical activity. Owing to the effective S doping (1.7-2.8 atom %), and the interconnected hollow meso-macroporous nanostructure, the resulting nanosized S-TiO2 exhibited unique adsorption properties and superior photocatalytic efficiency for the rapid degradation of hazardous organic dyes and phenols for water remediation. The presented strategy holds high potential to provide rapid production of a hierarchical and highly porous S-TiO2 photocatalyst on a large scale for various environmental remediation and other myriad photochemical applications.