Metal oxide nanoparticles, such as CuO and SnO 2 , are outstanding systems for H 2 S gas sensing in air. In this work, those nanoparticles were deposited with different mixing percentages on substrates to form percolating networks of nanoparticles. Electrical electrodes were deposited on the nanoparticles' films to investigate their gas sensing response against H 2 and H 2 S, and their electrical characteristics. The sensor devices based on CuO-SnO 2 nanoparticles revealed enhanced sensing characteristics against H 2 S with a sensitivity of 10 ppm. The enhanced sensing characteristics could be attributed to the formation of PN-junctions among CuO and SnO 2 nanoparticles. The reasonable production cost (due to simple structure and cheap used materials), low power consumption (~ 1 µW for H 2 S at room temperature), high sensitivity, high response, and reasonable response time of the present sensors qualify them for practical implementation in portable gas sensing devices with enhanced characteristics.

No abstract

In this study, the influence of direct electric current on a microcapsule was investigated. The microcapsule consisted of a core from a calcium ion and sodium alginate (SA) complex and the microcapsule membrane was formed by the polyionic complexation of poly(methylene-co-guanidine) (PMCG) and cellulose sulfate (CS). Microcapsules showed swelling and decreasing mechanical properties under the applied electric current, and the microcapsule membrane showed anisotropic swelling on the electrode side. The effect is attributed to an electrokinetic phenomenon, predominant formation of hydroxyl ions, and the diffusion of hydrated ions. The swelling degree of the microcapsule and microcapsule membrane at different pH and the applied electric current under alkali and acidic conditions was investigated. The swelling degree was influenced by the dissociation of the membrane, which was observed after applying the electric field, which was caused by the electrokinetic effect and the neutralization of the polycation (under alkali conditions) or polyanionic (under acidic conditions) segment during membrane formation.

Qatar is a country with limited area and number of settlements. It has witnessed rapid development since the 1950s centred on Doha as a result of the exploitation of its petroleum resources. An outcome of the process was the lack of attention paid to conservation, leading to the loss of valuable heritage resources. Realization of the situation has led to concerted efforts to improve retention. Questions that arise from need for action include: what constitute heritage and how should documentation be carried out? This article contributes to answering these questions based on the documentation of the Al-Zaman house by a team from Qatar University. The article explores the potential of using affordable peripheral methods such as photo-modelling in documentation and examines the role that buildings constructed during periods of historical transition play in the construction of social identity. Analysis shows that such buildings capture the zeitgeist of an era and so form an important part of history and identity. It was also established that photo-modelling is inappropriate for use as a tool in documenting heavily decorated buildings that are in a state of dilapidation due to problems of clarity of textures and patterns.