Equimolar Ratio Research Articles

Effect of composition and calcination on the enzymeless glucose detection of Cu-Ag bimetallic nanocomposites

Development of novel materials that are capable of sensing blood glucose in absence of enzymes could be highly beneficial for affordable diabetic care. The present work discusses the effect of composition and heat treatment on the glucose sensing ability of bimetallic Cu-Ag nanocomposites. Polyol reduction method was employed to prepare nanocomposites with five different Cu:Ag molar ratios viz. 1:1, 2:1, 3:1, 1:2 and 1:3. The nanocomposites were thoroughly characterized by XRD, XPS, EDS, and TEM imaging. The nanocomposite having equimolar ratio of Cu and Ag was the best glucose sensing material among the prepared samples having a high sensitivity of 1340 μA mM−1 cm-2 with a detection limit of 0.6 μM at S/N = 3. The nanocomposite exhibited exhibited noticeable linear response for glucose concentration ranging from 0.01–30 mM, with R2 value of 0.9926. It also showed very high selectivity, stability and good reproducibility with a very low sensitivity loss of 4.1 % after 20 days. A good correlation was obtained with the pathology laboratory data for real blood samples. Moreover, a three-fold increase in sensitivity was observed on calcining the nanocomposite at 600 °C making this sample one of the best sensor materials having high sensitivity, low detection limit with vast linear response range.

Structure and Properties of Carboxymethyl Chitin in the Salt, Acid, and Mixed Forms

Different forms of 6-О-carboxymethyl chitin were prepared, namely, the salt form containing, the carboxy group in the –COONa form, the acid form containing the carboxy group in the –COOН form, and the mixed form containing the units in the acid and salt forms in the equimolar ratio. The composition and structure of the synthesized carboxymethyl chitin and films based on them were confirmed by Fourier IR spectroscopy, solid-state 13C NMR spectroscopy, thermal gravimetric analysis, and differential scanning calorimetry. The mechanical properties of the films prepared from 6-О-carboxymethyl chitin in the salt and acid forms were evaluated by comparing their deformation characteristics. The Fourier IR data confirm formation of hydrogen bonds and ion pairs in 6-О-carboxymethyl chitin in the acid form as a result of intermolecular interaction of functional groups of the polymer. The solid-state 13С NMR data show that the substitution of the –СН2СООNa group for hydroxyl proton in the course of the synthesis of 6-О-carboxymethyl chitin from chitin occurs exclusively at the С-6 atom of the glucopyranose ring. Comparison of the data of thermal gravimetric analysis and differential scanning calorimetry shows that the amount of water absorbed by the polymer depends on the form in which 6-О-carboxymethyl chitin occurs, with the salt form being the most hygroscopic. The deformation characteristics of films of 6-О-carboxymethyl chitin in the salt and acid forms were studied. The elastic modulus of 6-О-carboxymethyl chitin in the acid form significantly differs from that of 6-О-carboxymethyl chitin in the salt form. This difference may be due to higher content of water absorbed by the polymer in the films obtained from the salt form of 6-О-carboxymethyl chitin (20%) compared to the films obtained from the acid form of 6-О-carboxymethyl chitin (9%).

Self-Assembly of Switchable Protein Nanocages via Allosteric Effect

Protein cages have promising applications in highly efficient gene transportation. Many methods of engineering protein–interface interactions have been developed to build such viral mimics. Missing...

High concentration of the ester-linked ω-hydroxy ceramide increases the permeability in skin lipid model membranes

The ester-linked ω-hydroxy acyl chain linked to a sphingosine base referred to as CER EOS is essential for the skin barrier lipid organization. While the majority of the skin lipids form a dense, crystalline structure, associated with low permeability, the unsaturated moiety of CER EOS, (either the linoleate or the oleate chain) exists in a liquid phase at the skin's physiological temperature. Thus, the relationship between CER EOS and barrier function is not entirely comprehended. We studied the permeability and lipid organization in skin lipid models, gradually increasing in CER EOS concentration, mixed with non-hydroxy sphingosine-based ceramide (CER NS) in an equimolar ratio of CERs, cholesterol, and free fatty acids (FFAs) mimicking the ratio in the native skin. A significant increase in the orthorhombic-hexagonal phase transition temperature was recorded when CER EOS concentration was raised to 70 mol% of the total CER content and higher, rendering a higher fraction of lipids in the orthorhombic phase at the expense of the hexagonal phase at physiological temperature. The model's permeability did not differ when CER EOS concentration ranged between 10 and 30% but increased significantly at 70% and higher. Using CER EOS with a perdeuterated oleate chain, it was shown that the fraction of lipids in a liquid phase increased with CER EOS concentration, while the neighboring CERs and FFAs remained in a crystalline state. The increased fraction of the liquid phase therefore, had a stronger effect on permeability than the increased fraction of lipids forming an orthorhombic phase.

High-temperature toughening in ternary medium-entropy (Ta1/3Ti1/3Zr1/3)C carbide consolidated using spark-plasma sintering

ABSTRACT We report for the first time the effect of temperature on the mechanical properties of (Ta1/3Ti1/3Zr1/3)C carbide. Flexural strength and fracture toughness were investigated using the three-point bending technique in argon. Using commercially available carbide powders with an equimolar ratio and performing spark plasma consolidation at 1973°C, we obtained a bulk single-phase medium-entropy carbide ceramic with the lattice parameter a= 4.458 Å. The flexural strength and fracture toughness at room temperature reached on average 700 MPa and 3.2 MPa m1/2, respectively. At 1800°C, local decomposition of the medium-entropy carbide took place as a structure with a local chemical gradient was observed after high-temperature tests, which increased fracture toughness by 30% (to 4.4 MPa m1/2).

Spectroscopic Methodology and Molecular Docking Studies on Changes in Binding Interaction of Felodipine with Bovine Serum Albumin Induced by Cocrystallization with β-Resorcylic Acid.

In the present study, a novel cocrystal of felodipine (FEL) and β-resorcylic acid (βRA) was developed. We specially focused on the change of binding pattern with bovine serum albumin (BSA) induced by cocrystallization of FEL with βRA. The solid characterizations and density functional theory (DFT) simulation verified that FEL-βRA cocrystal formed in equimolar ratio (1 : 1 M ratio) through C=O…H-O hydrogen bond between C=O group in FEL and O-H group in βRA. The binding interactions between FEL-βRA system and BSA were studied using fluorescence spectral and molecular docking methods. Two guest molecule systems, including a physical mixture of FEL and βRA and FEL-βRA cocrystal were performed binding to BSA in molecular docking. According to the Kb and binding energy, the supramolecular form of FEL-βRA system was retained during binding to BSA. Molecular docking simulation suggested that FEL and its cocrystal inserted into the subdomain IIIA (site II') of BSA. The interactions between FEL and BSA including hydrogen bonding with ASN390 residue and intermolecular hydrophobic interactions with LEU429 and LEU452 residues. However, the size of supramolecular FEL-βRA better matched that of active cavity of BSA; the cocrystal is closely bound to BSA through hydrogen bonding with ASN390 residue and intermolecular hydrophobic interactions with LEU429, VAL432, LEU452 and ILE387 residues. This change on binding affinity of FEL to BSA induced by cocrystallization with βRA provided theoretical basis to evaluate the transportation, distribution and metabolism of cocrystal drug.

A comparative study of palladium-based coordination compounds with bidentate (N,N, P,P and P,O) ligands; Design, synthesis, X-ray structural, catalytic activity and DFT studies

This account describes our recent studies on four new asymmetric cyclometallated Pd(II) complexes with a formula [L1 → Pd ← L2](ClO4) (L1 = benzylamine and L2 = bis (diphenylphosphino) methane oxide (dppmo) (3), 1,2-bis (diphenylphosphino) ethane (dppe) (4), bispyridine (bipy) (5) and 1, 10-phenanthroline (phen) (6)). These complexes have been prepared by the reaction of palladium(II) acetate with benzylamine ligand in equimolar ratios in toluene produced the [Pd(C6H4CH2NH2)(µ-OAc)]2 complex 1. A metathesis reaction between complex 1 and NaCl in water/acetone (1:10) exchanged the acetato ligands of 1 with chloro ligands. This produced the dinuclear cyclopalladated compound [Pd(C6H4CH2NH2)(µ-Cl)]2 complex 2. The following addition of dppmo, dppe, bipyridine and phenanthroline ligands, respectively, to the solution of 2 in CH2Cl2 generated the corresponding complexes. These complexes have been fully characterized by FT-IR, 1H, 13C and 31P NMR spectroscopic methods and other conventional techniques such as elemental analysis (CHN). Further, the solid-state structure of the complex 3 was determined by the single-crystal X-ray diffraction methods, showing that this complex consist of two five-membered rings formed by coordination of the dppmo ligand through the one phosphorus atom and one oxygen atom and coordination of the benzylamine ligand through the one carbon atom and one nitrogen atom to the metal center. Therefore, the catalytic activity of complex 3, using Suzuki and Heck coupling reactions, has been evaluated and compared. Using theoretical methods the structures of the asymmetric palladacycle complexes [L1 → Pd ← L2](ClO4) with different coordination mode, (where L1 = benzylamine (N,C coordination) and L2 = dppmo (P,O coordination) (3), dppe (P,P coordination) (4) and phen (N,N coordination) (6)), were compared with each other. In this regard density function theory (DFT) calculations at the BP86/def2-SVP level of theory were applied. The strength and nature of donor-acceptor bonds between the L1 and L2 and Pd fragments in the [L1 → Pd ← L2](ClO4) were carried out by natural bond orbital analysis (NBO) and energy-decomposition analysis (EDA) as well as their natural orbitals for chemical valence variation (EDA-NOCV).

Selective antifungal and antibacterial activities of Ag-Cu and Cu-Ag core–shell nanostructures synthesized in-situ PVA

A simple chemical reduction method was employed to synthesize Cu–Ag and Ag-Cu core–shell nanostructures inside polyvinyl alcohol (PVA) matrix at room temperature. The core–shell nanostructures have been synthesized by varying the two different concentrations (i.e. 0.1 and 0.01 M) of the respective metal ions in equimolar ratios using successive reduction with hydrazine hydrate (HH) as a reducing agent. The core–shell nanostructures have been further characterized by different characterization techniques. The UV–visible spectroscopy exhibit the respective shift in the band positions suggesting the formation of core–shell nanostructures, which was further confirmed by field emission transmission electron microscopy–high-angle-annular dark field elemental mapping.The effect of metal ion concentration of the core–shell nanostructure on various Gram positive and Gram negative bacteria like Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and one fungal species Aspergillus fumigatus was observed by performing MIC and MBC/MFC study. Cu-Ag core–shell nanostructures were found to be effective antibacterial agent against all tested Gram-positive and Gram-negative bacteria, whereas Ag-Cu core–shell nanostructures were more efficient against a particular fungal species known as A. fumigatus. The highest value of MIC (75 µg ml−1) for Ag-Cu 0.1M core shell nanostructures (D1) was noted against S. aureus and E. coli whereas the lowest value (20 µg ml−1) was observed with P. aeruginosa. While in case of Cu-Ag 0.1M core shell nanostructures (E1) the highest value of MIC (100 µg ml−1) was noted against S. aureus and P. aeruginosa whereas the lowest value (15 µg ml−1) was observed with A. fumigatus.Also, field effect scanning electron microscope (FESEM) images of untreated and core–shell nanoparticles treated micro-organisms showed that 0.1 M Ag-Cu and 0.1 M Cu-Ag core–shell nanostructure can successfully break the cell wall of the fungi A. fumigatus and bacteria P. aeruginosa, respectively. Thus the present study concludes that, Cu-Ag & Ag-Cu core–shell nanostructures damage the cell structure of micro-organisms and inhibits their growth. Hence, the present Cu-Ag & Ag-Cu core–shell nanostructure acts as good antimicrobial agent against the bacteria and fungi, respectively.

Pentacoordinated diorganotin(IV) complexes resulting from tridentate (NOO) donor Schiff bases: Synthesis, characterization, in vitro antioxidant, antimicrobial activities, and QSAR studies

A series of diorganotin(IV) complexes of type R2SnL, (where R = Me, Et, Bu and Ph) were prepared by the reaction of tridentate (NOO) donor Schiff base ligands with diorganotin(IV) dichloride in an equimolar ratio. The products were characterized by various spectroscopic techniques and physical and analytical methods (UV–vis, FTIR, NMR, fluorescence, elemental analysis). Spectroscopic data suggest that the Schiff base acts as a tridentate ligand (NOO) coordinated with a central tin atom via two oxygen and one imine nitrogen atom in a pentacoordinated fashion. The synthesized compounds were assayed for their in vitro antimicrobial activity against bacterial and fungal strains. All the compounds displayed promising results with the complexes being more potent than free ligands. The antioxidant activity of the compounds was determined by interaction with 2,2-diphenyl-1-picrylhydrazyl free radical. Complex Ph2SnL3 (16) was found to have the most potential antimicrobial activity against all tested strains and also exhibited excellent antioxidant activity. Quantitative structure–activity relationship of compounds was studied for antimicrobial activity with molar refractivity indices as significant statistical parameter.

Studies on Deactivation of Iron Oxide Catalyst in Solvent-Free N-Benzylation of Aniline with Benzyl Chloride

Nano-α-Fe2O3 prepared using acid pickling waste as precursor was found to be an effective catalyst for benzylation aniline with benzyl chloride. However, the formation of a green solution was observed during the solvent-free benzylation. A yellow-green single crystal as a byproduct was recovered from the green reaction mixture and characterized by X-ray single crystal diffraction, 1H NMR, FT-IR and elemental analysis. The results showed that this single crystal was a composite structural complex constructed by [(C6H6–CH2)2NH–C6H6]FeCl4 and [(C6H6–CH2)2NH–C6H6]Cl in equimolar ratio. The formation of the complex led to the deactivation and non-reusability of α-Fe2O3 catalyst for catalyzing solvent-free N-benzylation of aniline with benzyl chloride. The forming mechanism of the crystal was also discussed.

Effect of hydrogen-bond strength on photoresponsive properties of polymer-azobenzene complexes

Supramolecular complexation between photoresponsive azobenzene chromophores and a photopassive polymer host offers synthetic and design advantages compared with conventional covalent azo-containing polymers. In this context, it is important to understand the impact of the strength of the supramolecular interaction on the optical response. Herein, we study the effect of hydrogen-bonding strength between a photopassive polymer host [poly(4-vinylpyridine), or P4VP] and three azobenzene analogues capable of forming weaker (hydroxyl), stronger (carboxylic acid), or no H-bonding with P4VP. The hydroxyl-functionalized azo forms complete H-bonding complexation up to equimolar ratio with VP, whereas the COOH-functionalized azo reaches only up to 30% H-bond complexation due to competing acid dimerization that leads to partial phase separation and azo crystallization. We show that the stronger azo-polymer H-bonding nevertheless provides higher photoinduced orientation and better performance during optical surface patterning, in terms of grating depth and diffraction efficiency, when phase separation is either avoided altogether or is limited by using relatively low azo contents. These results demonstrate the importance of the H-bonding strength on the photoresponse of azopolymer complexes, as well as the need to consider the interplay between different intermolecular interactions that can affect complexation.

Isatin Endowed Metal Chelates as Antibacterial and Antifungal Agents

A new series of 5-chloroindoline-2,3-dione (isatin) derived ligands (L1 )-(L4 ) were prepared by reacting isatin with various diamines such as ethane-1,2-diamine, propane-1,3-diamine, butane-1,4-diamine, and benzene-1,2-diamine in an equimolar ratio to give 3-[(2-aminoethyl)imino]-5-chloro-1,3-dihydro-2H-indol-2-one (L1 ), 3-[(3-aminopropyl) imino]-5-chloro-1,3-dihydro-2H-indol-2-one (L2 ), 3-[(4-aminobutyl)imino]-5-chloro-1,3-dihydro-2H-indol-2-one (L3 ) and 3-[(2-aminophenyl)imino]-5-chloro-1,3-dihydro-2H-indol-2-one (L4 ). All ligands acted as tridentate possessing three active sites, isatin-O, azomethine-N, and amino-N for binding with the metal atoms. The structures of the isatin based Schiff bases were elucidated through their spectral (infrared, ultraviolet, nuclear magnetic resonance, and mass spectra), physical (melting point and solubility) and analytical (C, N, H %) data. The prepared ligands were reacted with Co(II), Ni(II), Cu(II), and Zn(II) transition metals in 1:2 molar ratio (metal:ligand) to form their complexes. IR, UV, NMR, conductance, magnetic moment, and elemental analysis was used to characterize the metal complexes. Metals based isatins were evaluated for their in-vitro antimicrobial properties against selected fungal and bacterial species. The anti-bacterial and anti-fungal results showed the metal chelates to be more biologically active than their parent uncomplexed ligands.

Molecular Crystal Forms of Antitubercular Ethionamide with Dicarboxylic Acids: Solid-State Properties and a Combined Structural and Spectroscopic Study.

We report on the preparation, characterization, and bioavailability properties of three new crystal forms of ethionamide, an antitubercular agent used in the treatment of drug-resistant tuberculosis. The new adducts were obtained by combining the active pharmaceutical ingredient with three dicarboxylic acids, namely glutaric, malonic and tartaric acid, in equimolar ratios. Crystal structures were obtained for all three adducts and were compared with two previously reported multicomponent systems of ethionamide with maleic and fumaric acid. The ethionamide-glutaric acid and the ethionamide-malonic acid adducts were thoroughly characterized by means of solid-state NMR (13C and 15N Cross-Polarization Magic Angle Spinning or CPMAS) to confirm the position of the carboxylic proton, and they were found to be a cocrystal and a salt, respectively; they were compared with two previously reported multicomponent systems of ethionamide with maleic and fumaric acid. Ethionamide-tartaric acid was found to be a rare example of kryptoracemic cocrystal. In vitro bioavailability enhancements up to a factor 3 compared to pure ethionamide were assessed for all obtained adducts.

Coordination Chemistry and Methylation of Mixed-Substituted Tetraphosphetanes (RP-PtBu)2 (R=Ph, Py).

Synthesis of mixed‐substituted tetraphosphetanes (RP−PtBu)2 (R=Ph (4), Py (5); Py=2‐pyridyl) is achieved from the condensation of dipyrazolylphosphanes RPpyr2 (R=Py (1), Ph (3); pyr=3,5‐dimethylpyrazolyl) as P1‐building block (R−P) and tBuPH2 in an equimolar ratio. Compound 5 is of special interest since the presence of two pyridyl‐substituents as well as the P4‐core allows for a rich coordination chemistry with coinage metal salts [Cu(MeCN)4][OTf], Ag[OTf] and in situ formed [Au(tht)][OTf] (tht=tetrahydrothiophene). Both tetraphosphetanes undergo alkylation reaction with MeOTf to give a series of tetraphosphetanium and tetraphosphetanediium triflate salts with additional methylation of the pyridyl‐moiety in case of 5 resulting in interesting novel cyclic trications. Harsh reaction condition and an excess of MeOTf converts 5 into the cyclic trication [‐P(MePy)PMe2P(MePy)PtBu‐]3+ (13 3+; MePy=1‐methylpyridiniumyl) through the elimination of isobutene. This salt undergoes a complicated rearrangement reaction involving a P−P/P−P bond metathesis to form trication [‐P(MePy)3PtBu‐]3+ (17 3+) when reacted with Me2PPMe2.

Novel dithiocabamate nano Zn(II), Cd(II) and Hg(II) complexes with pyrrolidinedithiocarbamate and N,N-diethyldithiocarbamate

The reaction of the equimolar ratio of ammonium pyrrolidinedithiocarbamate {(NH4)PyDT} and sodium N,N-diethyldithiocarbamate (NaEt2DT) with the divalent ion salts of zinc, cadmium and mercury resulted in the complexes of the type [M(κ2-PyDT)(κ2-Et2DT)]; {M(II) = Zn, Cd, Hg}. These complexes were characterized using different techniques: elemental analysis, molar conductivity, FTIR, 1H NMR, 13C{1H} NMR and HSQC. The results demonstrate the bidentate chelating mode of the two dithiocarbamate ligands through the sulfur atoms to afford a tetrahedral geometry around the metal ion. Surprisingly, these coordination compounds were obtained as nanocomplexes with regular geometrical nanostructures as follows; [Zn(κ2-PyDT)(κ2-Et2DT)] (1) as nanosheets with a thickness of 21–24 nm, [Cd(κ2-PyDT)(κ2-Et2DT)] (2) as nanorods with a diameter of 70–380 nm while [Hg(κ2-PyDT)(κ2-Et2DT)] (3) was found as merged nanospheres with a diameter of 54–70 nm. These nanostructures have been demonstrated using the SEM and X-ray diffraction of the powder.

Synthesis and Characterization for New Nanometer Cu(II) Complexes, Conformational Study and Molecular Docking Approach Compatible with Promising in Vitro Screening

Synthesis for new Cu(II) complexes from acetamidopyridine derivitives and their characterization. Applying analytical, spectral and conformational techniques, the characterization for all new synthesizes, was achieved. Equimolar ratio (1:1) was proposed for all complexes in which the ligands behaved as bidentate toward copper center. The molar conductivity measurements defined state of acetate presence according to coordination sphere. Two structural forms were proposed for five complexes, square-planer and octahedral based on UV–Vis and ESR data. Conformational study was executed for all compounds by DFT method in Gaussian 09 under 6-31G basis set. The optimal structural forms were obtained besides other significant files (log, chk & fchk). Also, functional parameters were calculated, to put a well view about physical features. QSAR parameters were obtained from HyperChem program, also to assert on some characteristics. MOE-docking module, which considered the most powerful program simulates interaction of tested compound with biological systems, was also used to strengthen the study. The data extracted orient to great expectation for biological efficiency of complexes against breast cancer cells. The most shining point was the anticancer screening results, which reflect vigorous toxic behavior for most tested complexes against breast cancer cell line that actually exceeds than doxorubicin itself.

Ge30AsxSe70-x bulk glasses from the point of view of chemistry

To elucidate the chemical structure of Ge-As-Se based glasses with selenium substoichiometry, Ge30AsxSe70-x homogeneous bulk glasses were prepared and the glass-forming region was found from x ​= ​0 up to 40. The chemical structure of these glasses was characterized by basic structural units. The structure of Ge30Se70 (x ​= ​0) glass is based on GeSe4/2 and GeSe4 structural units and traces of selenium. When selenium is gradually replaced with arsenic AsSe3/2 and GeIIAs2/3 structural units appear in the equimolar ratio with gradually increasing concentrations at the expense of the units with Ge–Se bonds. Finally, for x ​= ​40 the glass is formed exclusively by structural units AsSe3/2 and GeAs2/3. Thus, the structure of both border glasses is based only on two structural units whereas other glasses are based on four units. For this reason, the undercooled melts of both border glasses are less stable and undergo crystallization when heated. In terms of the geometry of the basic structures, the structure for x ​= ​0 is formed solely by tetrahedral units with germanium as the central atom, and then is gradually transformed with increasing concentration of arsenic to a structure consisting only of trigonal pyramids with arsenic as a central atom.

Removal of nickel through sulfide precipitation and characterization of electroplating wastewater sludge

Abstract This work consists of the removal of nickel by sulfide precipitation from industrial electroplating wastewater and characterization of the produced sludge. Tests are carried out in a perfectly stirred batch reactor on electroplating industrial solution and synthetic solution prepared in the laboratory. The aim is to evaluate the impact of complexing agents formed during precipitation of metal ions in the industrial effluent. The concentration of nickel in both solutions is 100 mg/L. The operating conditions for the sulfide precipitation process are optimized: pH, molar ratio [S=]/[Ni2+] and dosage of S= ions. For an initial pH of 5 and an equimolar ratio of [S=]/[Ni2+]:1/1, the results show that the removal efficiency of Ni2+ ions is approaching 91 and 94% for industrial and synthetic solutions, respectively. Otherwise, for the same pH value in supersaturation conditions ([S=]/[Ni2+]:1.5/1), the removal efficiency is approaching 62 and 92% for industrial and synthetic solutions, respectively. For an effective metal removal, the optimal dosage of sulfide ions was evaluated. For 33 mg/L of S=, the removal efficiency of Ni2+ is approximately 90%. The resulting sludge has been characterized by X-ray diffractometry, scanning electron microscopy, infrared spectroscopy and thermal analysis. It consists essentially of millerite and nickel oxide.

Determination of the stereoisomeric distribution of R-(−)- and S-(+)-methamphetamine in Thai pills in the legal context of “not inconsiderable quantities"

In Germany, the severity of a narcotic offence is determined based on the classification into different categories of quantity. Recently, an amendment to the Narcotics Law regarding the “not inconsiderable quantities” was introduced. The new limits for methamphetamine are derived from the varying potency of the respective enantiomers. Switzerland, however, does not practice this distinction and there is only one limit quantity, without considering the isomeric structure. To examine whether this single value is still contemporary, 26 Thai pill samples from the years 2000, 2001, 2007, 2009 and 2017 were analyzed by HPLC-MS/MS and GC-MS.Both methods resulted in similar stereoisomeric distributions: the pills mainly consist of the more potent S-(+)-methamphetamine, some even being enantiopure. Others show enantiomeric mixtures of R-(−)-/S-(+)-methamphetamine, but rarely in an equimolar ratio. There even was one sample, where mainly the less potent R-(−)-methamphetamine was detected.In conclusion, the analyses revealed that the single value for a “not inconsiderable quantity” in Switzerland seems outdated. Most of the sized pills showed a much higher concentration of the more potent S-(+)-methamphetamine. The risks related to taking such a pill are much higher and therefore the limit quantity should be adapted to the potency of the respective enantiomers.

Polymer-dispersant-stabilized Ag nanofluids for heat transfer applications

One-step wet chemical method has been employed for the synthesis of silver (Ag) nanofluids followed by the preparation of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and PVP–PVA mixed-dispersant-stabilized nanofluids by varying the concentration ratio of dispersants for the viscosity and thermal conductivity analysis. The optical absorption studies indicate the presence of nanoparticles in the prepared fluids (or the formation of the silver nanoparticles). The shape and size of the nanoparticles are confirmed by the field emission scanning electron microscopy, and the particle size distribution and zeta potential analysis were carried out by using dynamic light scattering. It is observed that the thermal conductivity of Ag nanofluids increases with an increase in the dispersant concentration with respect to the temperature. The maximum thermal conductivity enhancement of Ag nanofluids was observed in the presence of an equimolar ratio of PVP–PVA (1:1:1) blends as stabilizers.Graphic abstract