Room temperature LPG resistive sensor based on the use of a few-layer graphene/SnO<Subscript>2</Subscript> nanocomposite

A nanocomposite consisting of a few layers of graphene (FLG) and tin dioxide (SnO₂) was prepared by ultrasound-assisted synthesis. The uniform SnO₂ nanoparticles (NPs) on the FLG were characterized by X-ray diffraction in terms of lattice and phase structure. The functional groups present in the composite were analyzed by FTIR. Electron microscopy (HR-TEM and FE-SEM) was used to study the morphology. The effect of the fraction of FLG present in the nanocomposite was investigated. Sensitivity, selectivity and reproducibility towards resistive sensing of liquid propane gas (LPG) was characterized by the I-V method. The sensor with 1% of FLG on SnO₂ operated at a typical voltage of 1 V performs best in giving a rapid and sensitive response even at 27 °C. This proves that the operating temperature of such sensors can be drastically decreased which is in contrast to conventional metal oxide LPG sensors.

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Graphical abstract Schematic of a room temperature gas sensor for liquefied petroleum gas (LPG). It is based on the use of a few-layered graphene (1 wt%)/SnO₂ nanocomposite that was deposited on an interdigitated electrode (IDEs). A sensing mechanism for LPG detection has been established.

     

Fixed-Point Technique for Implicit Complementarity Problem in Hilbert Lattice

In this paper, we consider and study the implicit complementarity problem in the setting of a Hilbert lattice. It has been shown that this problem can be formulated as a fixed-point problem by using a suitable change of variables. Moreover, this formulation allows us to prove the existence and uniqueness of solutions of the implicit complementarity problem.     

Synthesis and Cytotoxic Activity of Novel Pyrazoline Derivatives against Human Lung Tumor Cell Line (A549)

In the present investigation, a series of 5‐(‐4‐(substituted)phenyl)‐3‐(4‐hydroxy‐3‐methylphenyl)‐4,5‐dihydro‐1H‐1‐pyrazolyl‐2‐toluidino methane thione and 5‐(substituted)phenyl‐3‐(4‐hydroxy‐3‐methylphenyl)‐4,5‐dihydro‐1H‐1‐pyrazolyl‐2‐methoxy anilino methane thiones were synthesized and were examined against human lung tumor cell line (A549) in vitro using the MTT assay system. Among those tested, 5‐(4‐flurophenyl)‐3‐(4‐hydroxy‐3‐methylphenyl)‐4,5‐dihydro‐1H‐1‐pyrazolyl‐2‐toluidino methane thione & 5‐(4‐chlorophenyl)‐3‐(4‐hydroxy‐3‐methylphenyl)‐4,5‐dihydro‐1H‐1‐pyrazolyl‐2‐methoxy anilino methane thione showed more potent cytotoxicity against human lung tumor cell line (A549) than the other synthesized compounds.     

Silver Cyanide Complexes of Heterocyclic Thiones

Silver(I) cyanide complexes of various thiones (imidazolidine-2-thione, diazinane-2-thione and their derivatives) have been prepared and characterized by elemental analysis, i.r. and n.m.r. (¹H, ¹³C, ¹⁵N and ¹⁰⁷Ag) spectroscopy. It appears from the i.r. data that six out of the ten complexes are nonionic [>C=S—Ag—CN] while the remaining four exist as ionic species [Ag(>C=S)₂]⁺[Ag(CN)₂]^– in the solid state. An upfield shift in the ¹³C-n.m.r. and downfield shifts in the ¹H-, ¹⁵N- and ¹⁰⁷Ag-n.m.r. spectra are consistent with the sulfur coordination to silver(I). The n.m.r. data shows that the [>C=S—AgCN] complexes are stable in solution and do not undergo redistribution.     

Effects of Organic Salts on the Rate of Alkaline Hydrolysis of Phthalimide in the Presence Ofcationic Micelles

Pseudo-first order rate constants (k_obs) for alkaline hydrolysis of phthalimide (PTH), obtained at constant concentration of cetyltrimethylammonium bromide (CTABr) and 35°C, vary with the concentration of organic salts ([MX]) according to the relationship: k_obs = (k₀ + K [MX])/(1 + K [MX]) where and K are empirical parameters. The values of K at 0.01 M CTABr are nearly 2 times larger than the corresponding K values at 0.02 M CTABr for sodium benzoate, disodium phthalate and disodium isophthalate.     

The reaction of aroylhydrazines with N-phenylsulfonylarenehydrazonoyl chlorides. A route to substituted 4-amino-(4H)-1,2,4-triazoles and 1,3,4-oxadiazoles

Treatment of N-phenylsulfonylarenehydrazonoyl chlorides (II) with equivalent amounts of aroylhydrazines (III) in ethanol gave 3,5-diaryl-4-phenylsulfonylamino-1,2,4-triazoles (IV). Reaction of II with two equivalents of III in tetrahydrofuran gave 2,5-diaryl-1,3,4-oxadiazoles (V), in addition to IV. Addition of triethylamine to II or its mixture with III yielded only the tetrazenes (VIII). The possible pathways leading to IV-V and VIII are discussed. J. Chem. Soc., 14, 1089 (1977)     

Synthesis of Some 1,3-Thiazole, 1,3,4-Thiadiazole, Pyrazolo[5,1-c]-1,2,4-triazine, and 1,2,4-Triazolo[5,1-c]-1,2,4-triazine Derivatives Based on the Thiazolo[3,2-a]benzimidazole Moiety

3-(3-Methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile was synthesized by refluxing ethyl 3-methylthiazolo[3,2-a]benzimidazole-2-carboxylate, acetonitrile, and sodium hydride. Treatment of 3-(3-methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile with phenyl isothiocyanate, in the presence of KOH, furnished the corresponding potassium salt which was converted into thioacetanilide derivative upon neutralization. The thioacetanilide derivative reacts with α-chloroacetylacetone and ethyl α-chloroacetoacetate to give the 1,3-thiazole derivatives, while the reaction of the'thioacetanilide derivative with hydrazonyl chlorides gave 1,3,4-thiadiazole derivatives. On the other hand, 3-(3-methylthiazolo[3,2-a]benzimidazol-2-yl)-3-oxopropionitrile reacted with the diazonium salt of both 3-phenyl-5-amino-(1H)-pyrazole and 5-amino-l,2,4-(1H)-triazole to afford the corresponding hydrazones. The latter hydrazones underwent an intramolecular cyclization upon boiling in pyridine to give pyrazolo[5,1-c]-1,2,4-triazine and 1,2,4-triazolo[5,1-c]-1,2,4-triazine derivatives. Moreover, the behavior of thiazolo[3,2-a]benzimidazol-3(2H)-one towards phenyl isothiocyanate followed by the reaction with α-chloroketones or hydrazonyl chlorides was investigated. Some of the latter compounds exhibited moderate effects against some bacterial and fungal species.     

Effect of gamma-irradiation on surface and catalytic properties of CuO−ZnO/Al2O3 system

A copper, zinc and aluminium mixed oxides sample having the nominal composition 0.25 CuO/0.03 ZnO/Al₂O₃ was prepared by impregnating Al(OH)₃ with copper and zinc nitrate solutions, drying at 100 °C then heating in air at 600 °C. The obtained solid was exposed to different doses of -rays (20–160 Mrad). The surface characteristics namelyS _BETV_P andr of different treated adsorbents were determined from N₂ adsorption isothems measured at –196 °C. The catalytic activity of various irradiated solids was determined by following up the kinetics of CO-oxidation by O₂ at 150–200 °C. The results showed that the doses up to 80 Mrad resulted in no significant change in theS _BET but increased slightly theV _P (20%) of the treated adsorbents. The irradiation at 160 Mrad caused an increase of 20% in theS _BET of the irradiated solid sample. The catalytic activity increased progressively by increasing the dose, a dose of 160 Mrad brought about an increase of 140% in the catalyst's activity. The apparent activation energy of the catalytic reaction decreased monotonically by increasing the absorbed dose of -rays which was attributed to a parallel induced decrease in the value of pre-exponential term of the Arrhenius equation. The observed increase in the catalytic activity due to -irradiation has been interpreted as a result of increasing the concentration of catalytically-active sites contributing in chemisorption and catalysis of CO-oxidation via a possible fragmentation of CuO crystallites.