EPR and ENDOR spectroscopy have been used to investigate a variety of trapped electron centers on the surface of polycrystalline MgO. The oxide was dehydrated under vacuum at different temperatures (673-1123 K) and UV irradiated under H 2 . The dehydration process results in the formation of surface anion vacancies, which subsequently act as excess electron traps (forming color centers). A variety of such color centers have been identified. At high activation temperatures (1123 K), surface F S + (H) color centers (type I) are formed, which have been assigned to an electron trapped by a specific anion vacancy. At slightly lower activation temperatures, a second F S + (H) color center (type II) predominates; this center has been assigned to an electron trapped in a higher coordinated surface vacancy. However, at low activation temperatures such that the oxide surface remains partially hydrated, different types of color centers are present. It is proposed that these centers arise from electron trapping at a surface cation-anion vacancy pair (tentatively assigned as P Scenters). The mechanism by which the latter center is effectively reduced by a single electron is unclear. The distribution and abundance of these different trapped electron centers varies as a function of the dehydration temperature. The results show that the surface of polycrystalline MgO containing a variety of point defects changes dramatically depending on the pretreatment conditions.

Abstract-Activated carbon has been known as an excellent adsorbent which has been widely used due for its large adsorption capacity and low cost. In Malaysia, palm kernel shell is one of the main agriculture wastes obtained from palm oil industries. In this study, the palm kernel shell-based activated carbon was prepared via microwave-induced activation process using phosphoric acid, H Index Terms-Activated carbon, palm kernel shells, microwave-induced, phosphoric acid.

High surface area activated carbon has always fascinated researchers for its application as adsorbent, for water purification, medical and industrial. Date is the major export of Saudi Arabia, while tons of date foliar and fronds are troublesome and yet to be disposed. Transforming this waste into usable activated carbon can be a good idea for recycling, sustainable and green chemistry. In this study, date tree frond is selected to prepare activated carbon, while the effect of phosphoric acid in chemical activation is studied. Using thermogravimetry analysis, it was found that 400oC was the best temperature to convert date frond to carbon. This is supported by FTIR spectroscopy. Various concentration of phosphoric acid is used to optimize the product high surface area carbon obtained and it was found the best is at 60% phosphoric acid with the highest surface area of 1139 m2g-1. This result is also supported by FTIR spectroscopy, which indicates the similarities between commercial carbon and the carbon prepared. FESEM pictographs show chemical activation using phosphoric acid can easily open up pores and cavity of the prepared activated carbon the get the high surface area. It is thus suggested that for mass production of high surface area carbon, date palm frond is used as the source of raw material, due to its abundance and availability comes from the pruning process on the date palm tree, while chemically activated to get the high surface area.

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A rotating cryostat has been used to generate several new naked metal clusters whose structures and reactions have been studied by EPR spectroscopy. Most alkali-metal trimers adopt an obtuse triangular geometry with a 2B2 ground state in CZv symmetry. A new acute Na, cluster was formed by interaction with water, Na,(H,O), where x 3 I . The first EPR spectrum of a mixed alkali-metal trimer, Na,Li, has been recorded. The fluxionality of both Na, and Li, in an adamantane matrix is lost and a static form results with the Li located at the apical position. The first ENDOR (electron nuclear double resonance) spectrum of a naked metal cluster, Li,, has been recorded. It gives more accurate paramagnetic parameters and shows conclusively that the cluster is a fluxional, pseudo-rotating Jahn-Teller molecule. The ENDOR spectra of Li,(H,O), complexes were also observed. A new coinage metal trimer, Au2Ag, has been characterised by EPR spectroscopy and has the silver in the apical position in a static obtuse structure. Reactions of the alkali-metal and coinage-metal trimers with simple molecules such as water and ethene resulted in a change in geometry from an obtuse or fluxional molecule to an acute static entity. The flexible nature of clusters is discussed in the context of modelling the chemical events occurring at the active metallic sites of heterogeneous catalysts. Experimental Principle of the rotating cryostat techniqueIn the matrix-isolation technique reactive and tethered in specific sites in the matrix species are trapped so that they cannot AXIS OF ROTATION DIRECTION OF ROTATION M A m SURFACEOF BANDCOVERED WITH REACTANT 'METAL 7 Basis of the presentation given at Dalton Discussion No. 1, 3rd-5th