Porous Structure and Fractal Dimensions of Activated Carbon Prepared from Waste Coffee Grounds.

The present work reports the results of a systematic study on the evolution of the morphological properties of porous carbons derived from coffee waste using a one-pot potassium-hydroxide-assisted process at temperatures in the range of 400-900 °C. Raw materials and obtained carbons were studied by TG, DTG, SEM and nitrogen adsorption porosimetry. The decomposition temperature ranges for hemicellulose, cellulose and lignin as the main component of the feedstock have been established. It is shown that the proposed method for the thermochemical treatment of coffee waste makes it possible to obtain activated carbon with a controllable pore size distribution and a high specific surface area (up to 1050 m2/g). A comparative study of the evolution of the distribution of pore size, pore area and pore volume has been carried out based on the BJH and NL-DFT (slit-like pores approximation) methods. The fractal dimension of the obtained carbons has been calculated by Frenkel-Halsey-Hill method for single-layer and multilayer adsorptions.

Cobalt ferrite as an electromagnetically boosted metal oxide hetero-Fenton catalyst for water treatment.

The cobalt ferrite Fenton catalysts were obtained by the flow co-precipitation method. FTIR, XRD, and Mössbauer spectroscopy confirmed the spinel structure. The crystallite size of the as-synthesized sample is 12 nm, while the samples annealed at 400 and 600 °C have crystallite sizes of 16 and 18 nm, respectively. The as-synthesized sample has a grain size of 0.1-5.0 µm in size, while the annealed samples have grain sizes of 0.5 µm-15 µm. The degree of structure inversion ranges from 0.87 to 0.97. The catalytic activity of cobalt ferrites has been tested in the decomposition of hydrogen peroxide and the oxidation of caffeine. The annealing of the CoFe2O4 increases its catalytic activity in both model reactions, with the optimal annealing temperature being 400 °C. The reaction order has been found to increase with increasing H2O2 concentration. Electromagnetic heating accelerates the catalytic reaction more than 2 times. As a result, the degree of caffeine decomposition increases from 40% to 85%. The used catalysts have insignificant changes in crystallite size and distribution of cations. Thus, the electromagnetically heated cobalt ferrite can be a controlled catalyst in water purification technology.

Eco-friendly synthesis of cobalt-zinc ferrites using quince extract for adsorption and catalytic applications: An approach towards environmental remediation.

Cobalt-zinc ferrite nanoparticles were synthesized using environmentally friendly approach with quince extract as a reducing agent. Crystal structure and morphology of the obtained materials were studied by XRD, SEM-EDS, Mössbauer and IR spectroscopy. The synthesized nanoparticles have a cubic spinel structure and crystallite size ranging from 5 to 9 nm. The infrared spectra contain characteristic absorption bands for the MA-O (∼560 cm-1) and MB-O bonds (∼420 cm-1). Force constants were calculated for both tetrahedral and octahedral bonds. As the Co content increases, the force constant for the tetrahedral bond increases and the force constant for the octahedral bond decreases. The obtained ferrite nanoparticles have good magnetization as shown by VSM (in the range from 36 to 67 emu/g). Magnetic nanoparticles CoxZn1-xFe2O4 were also tested for induction heating with electromagnetic field. The sample with x (Co) = 0.4 has the highest specific absorption rate. The synthesized samples were tested as adsorbents using the Congo Red dye as model pollutant. The best adsorbent was pure zinc ferrite with the adsorption capacity of 24.7 mg/g. The catalytic activity of the obtained ferrites for the decomposition of H2O2 was studied as well. The most active catalyst was pure cobalt ferrite. Probably, the active centers are octahedral cobalt ions. Thus, the obtained magnetic nanoparticles can be used for the adsorptive removal of pollutants, catalytic decomposition of the H2O2 and low-frequency hyperthermia.

Two-Step Spin Crossover in Hofmann-Type Coordination Polymers [Fe(2-phenylpyrazine)2{M(CN)2}2] (M = Ag, Au).

Two 2D Hofmann-type complexes of the composition [Fe(Phpz)2{M(CN)2}2] (where Phpz = 2-phenylpyrazine; M = Ag, Au) have been synthesized, and their spin-crossover (SCO) behavior has been thoroughly characterized. Single-crystal X-ray analysis reveals that these complexes contain a crystallographically unique Fe(II) center surrounded by two axial Phpz ligands and four equatorial cyanide [M(CN)2]- bridges. It is shown that, using of a ligand with two aromatic rings, an advanced system of weak supramolecular interactions (metal-metal, C-H···M, and π···π stacking contacts) is realized. This ensures additional stabilization of the structures and the absence of solvent-accessible voids due to dense packing. Both complexes are characterized by a highly reproducible two-step SCO behavior, as revealed by different techniques (superconducting quantum interference device magnetometry, optical microscopy, etc.). Research shows the exceptional role of the presence of various supramolecular interactions in the structure and the influence of the bulky substituent in the ligand on SCO behavior. Moreover, the perspective of substituted pyrazines for the design of new switchable materials is supported by this work.

Spin crossover in iron(II) Hofmann clathrates analogues with 1,2,3-triazole.

Hofmann-like cyanometallic complexes represent one of the biggest and well-known classes of FeII spin-crossover compounds. In this paper, we report on the first FeII Hofmann clathrate analogues with unsubstituted 1,2,3-triazole, which exhibit temperature induced spin transition. Two new coordination polymers with the general formula [FeII(1,2,3-triazole)2MII(CN)4] (M = Pt, Pd) undergo abrupt hysteretic spin crossover in the range of 190-225 K as revealed by magnetic susceptibility measurements. Two compounds are isostructural and are built of infinite cyanometallic layers which are supported by 1,2,3-triazole ligands. The thermal hysteresis loop is very stable at different scan rates from 0.5 to 10 K min-1. The compounds display strong thermochromic effect, changing their colour from pink in the low-spin state to white in the high-spin state. Our findings show that 1,2,3-triazole is suitable for elaboration of spin-crossover Hofmann clathrate analogues, and its use instead of more classical azines can advantageously expand this family of complexes.

Protective effects of alpha-ketoglutarate against aluminum toxicity in Drosophila melanogaster.

In recent years, Drosophila melanogaster has emerged as a model for studies on aluminum toxicity. The current study aimed to disclose the mechanisms of aluminum toxicity in D. melanogaster at larval and adult stages and examined the potential protective effects of dietary alpha-ketoglutarate (AKG). Flies were reared on food containing 10 mM AlCl3, 10 mM AKG or both additives. Rearing on an AlCl3-containing diet induced behavioral defects, and decreased fecundity and long-term survival of female flies. The addition of dietary AKG did not ameliorate locomotor and taste behavior defects or the higher sensitivity to oxidative stress, but improved heat stress resistance, egg-laying capability and survival of females treated with AlCl3. Metabolic effects of AlCl3 exposure on flies included an imbalance of metal content, decreased glucose levels, increased free iron and storage triacylglyceride (TAG) levels, mitochondria dysfunction, and the development of oxidative stress. Dietary AKG did not prevent AlCl3 effects on glucose and TAG, but improved metal homeostasis, inhibited the increase in free Fe and restored the functional activity of iron-containing enzymes such as aconitase. In addition, AKG decreased the intensity of oxidative stress seen in AlCl3-reared adult flies, probably due to inhibition of iron mobilization. The results show that AKG is not a full antidote against Al toxicity but is able to relieve multiple metabolic effects of high aluminum. Furthermore, the modulating ability of AKG can clearly be helpful in exploring the molecular mechanisms of Al toxicity.

The Effect of Sulphate Anions on the Ultrafine Titania Nucleation.

The phenomenological model of sulphate anions effect on the nanodispersed titania synthesis during hydrolysis of titanium tetrachloride was studied. It was proposed that both chelating and bridging bidentate complexes formation between sulphate anions and octahedrally coordinated [Ti(OH)h(OH2)6-h](4-h)+ mononers is the determinative factor for anatase phase nucleation.

MoS2/C Multilayer Nanospheres as an Electrode Base for Lithium Power Sources.

Multilayer nanospheres with alternating 2H-MoS2 and C layers were studied as a cathode base for lithium power sources. Interesting hierarchical structure, synergetic effect, and the presence of defects as supplementary active sites, introduced by the additional annealing at 773 K in Ar atmosphere, have determined the conductivity, referred to symmetric hopping or random barrier model, and led to achieve the high values of specific capacity of 3700, 1390, and 790 A h kg(-1) at currents 0.1, 0.3, and 0.5 C. Such unusual result was never reported before and could be explained by combining of the faradaic and non-faradaic accumulation processes within electrode material.