Jerzy P. Lukaszewicz

Novel nitrogen-containing mesoporous carbons prepared from chitosan

In this study, synthesis of novel nitrogen-containing mesoporous carbons with the use of both colloidal silica as a template and chitosan as a new promising carbon precursor was performed. The prepared materials were characterized by adsorption of nitrogen, high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy, Raman spectroscopy, and elemental analysis. The use of the silica template makes it possible to achieve products of the pore volume as high as 4.31 cm3 g−1, with only insignificant contribution of microporosity. The present method enables the synthesis of nitrogen-containing carbons in a simple manner, using an inexpensive and readily available biopolymer.

A LaF3-based oxygen sensor with perovskite-type oxide electrode operative at room temperature

Abstract LaF 3 -based oxygen sensors have been constructed by using perovskite-type oxides as new types of sensing electrode materials. The pulverized oxides are either fixed on the LaF 3 surface as a thin layer by means of a holder or applied on the LaF 3 surface after mixing with a binder (polystyrene or polyvinyl alcohol). The new electrodes exhibit efficient room-temperature operation, and LaCoO 3 and LaMnO 3 yield sensing electrodes with better sensing performance than a Pt electrode. The sensors sensitivity as well as the response time are greatly dependent on the oxide used. The sensing mechanisms derived from the Nernst plots correspond well to the activity of the oxides for the electrochemical reduction of oxygen in an alkaline solution.

Diode-type humidity sensor using perovskite-type oxides operable at room temperature

Abstract A novel humidity-sensitive element is described. Aiming at a humidity sensor of possibly small dimensions operable at room temperature, the sensing element is constructed of selected perovskite-type oxides and a metal needle. The oxide disc and the metal rod form a structure equivalent to an electronic diode. The current-voltage characteristic is sensitive to water vapour adsorption at room temperature. Several perovskite-type oxides and metals have been tested, but the most useful properties are exhibited by sensors consisting of a LaCrO3 oxide disc of moderate electric conductivity and Cu, Fe and Al needles. Application of highly conductive perovskite-type oxides does not result in the construction of a water vapour-sensitive diode of the structure described above.

Carbon-film-based humidity sensor containing sodium or potassium. Recovery effect

Abstract The paper describes the recovery effect of some modified carbon films applied as a humidity-sensitive resistor. The carbon films were prepared using mixtures of furfuryl alcohol and NaOH (or KOH) solution. The films have been tested as humidity-rensitive resistors. FT-IR investigations revealed that due to oxygen and carbon dioxide chemisorption the carbon surface was covered by polar surface functional groups. The electric resistance of such films with oxidised surface is extremely sensitive to contact with water vapour. On the contrary, the sensitivity of newly obtained Na (or K)-modified carbon films towards water vapour was found to be relatively minor before ageing. The process of humidity sensitivity development (caused by oxidation of carbon surface) is reversible, i.e., the sensitivity disappears upon HCl and/or heat treatment but recovers after a sufficiently long storage in air.

An application of carbon-type semiconductors for the construction of a humidity-sensitive diode

Abstract This paper describes an application of carbon-type semiconductors for the construction of humidity-sensitive diodes. The sensing diodes consist of two semiconducting layers with different electronic properties deposited onto a quartz substrate by means of the spray pyrolysis method. The main electronic properties of carbons, i.e., electrical conductivity, and the type of majority current carriers were estimated by a suitable heat treatment. This resulted in the construction of humidity-sensitive diodes exhibiting a typical voltage-current diode-like behaviour in the presence of moisture. Some water adsorption and electronic properties of single carbon layers are also presented and discussed in terms of the amplification effect of the diode junction.

The fungicidal properties of the carbon materials obtained from chitin and chitosan promoted by copper salts

Renewable raw materials chitin and chitosan (N-deacetylated derivative of chitin) were subjected to action of different copper modifiers that were carbonized in the atmosphere of the N2 inert gas. As a result of the novel manufacturing procedure, a series of carbon materials was obtained with developed surface area and containing copper derivatives of differentiated form, size, and dispersion. The copper modifier and manufacturing procedure (concentration, carbonization temperature) influence the physical-chemical and fungicide properties of the carbons. The received carbons were chemically characterized using several methods like low-temperature adsorption of nitrogen, X-ray diffraction analysis, scanning electron microscopy, cyclic voltammetry, elemental analysis, and bioassay. Besides chemical testing, some biological tests were performed and let to select carbons with the highest fungicidal activity. Such carbons were characteristic of the specific form of copper derivatives occurring in them, i.e., nanocrystallites of Cu(0) and/or Cu2O of high dispersion on the surface of carbon. The carbons may find an application as effective contact fungistatic agents in cosmetology, medicine, food industry, etc.

Discussion Remarks on the Role of Wood and Chitin Constituents during Carbonization

Nature is a source of some biomaterials like wood and chitin which can be successfully transformed into chars of advanced structural/surface parameters. The manuscript is discursive and suggests that particular components of the materials (cellulose, lignin, hemicellulose, alfa-chitin fibrils, mineral-protein matrix) play a specific role in the manufacturing of porous chars. It is proposed that some of the components (hemicellulose and mineral-protein matrixes) behave like a natural soft template during carbonization of wood and chitin. It is suggested why particular components and derivatives of wood and chitin (cellulose and chitosan) can not form porous carbonaceous matrixes when are carbonized separately.

Transfer of Triazine-iron(II) Chromic Complexes Left by Iron Items on Textile Background and Human Skin

Abstract:  The research is focused on the detection and transfer of iron traces left by iron items on clothing and human skin. The method is based on the formation of colored complexes between ferrous ions and five synthesized, mostly new triazines. Iron traces originally were left by iron rings on slightly wetted (artificial sweat) cotton fabrics and subsequently transferred to a separate textile substrate. Prior to the use of trazines the contact spots were treated with a new inorganic reducing agent (Sn2+) to reduce Fe3+ to Fe2+. The method is sensitive to detect iron traces on wetted canvas after 10 min contact with iron items. More spectacular results were obtained for traces left on human palm even after very short contact (10 sec). The new iron‐trace‐transfer method eliminated the contact of triazines solutions with human skin. Transmission visible spectra of Fe(II)–triazine complexes were determined.

1,2,4-Triazine-Based Chromogenic Reagents for the Detection of Microtraces of Various Metals Left on Human Skin*

Abstract:  This article extends the application of 1,2,4‐triazine‐based chromogenic reagents to the detection of nonferrous metal traces left on contact with canvas and human skin. The possibility of detection of iron traces resulting from contact with objects made of stainless steel was investigated as well. Additionally, the ability of triazines to form chromatic complexes with Zn2+, Ni2+, Co2+, Cu2+, Cr3+, and Al3+ ions was studied spectrophotometrically. Molar absorption coefficients, ranging from 8.8 to 29.9 × 103/M/cm, provide high sensitivity of 1,2,4‐triazines toward nonferrous ions, thus, enabling the detection at concentrations as low as a few μM. The method was sensitive enough to detect traces resulting from a 1‐min contact with a stainless steel made object, which is commonly considered as a corrosion‐resistant material. The amounts of metal ions transferred to the skin after a 2‐min contact with objects made of brass, zinc, and copper were sufficient to develop chromatic imprints.

Preparation and characterization of polymers imprinted molecularly with ibuprofen and nitrobenzene

In this work molecularly imprinted polymer (MIP) which can be later used for SPME improvement were prepared. Polymerization reaction was initiated in six different ways and for this purpose six different solvents as porogens were used. Prepared MIP’s were stable in temperature range 160–200°C. Pore sizes and BET surface were characterized by sorption of nitrogen at liquid nitrogen temperature. On the contrary to most MIPs, the studied MIPs were strictly nanoporous i.e. most of total pore volume was attributed to pores ranging from 3 to 1.0 nm in diameter. BET surface area exceeded even 300 m2/g. Basic conditions of the MIPs synthesis have been optimized with particular respect to type of solvent and polymerization initiator which are basic factors influencing the ability of the MIP towards adsorption of ibuprofen/nitrobenzene.