Highly efficient photoinduced desorption of N2O and CO from porous silicon

Abstract

Photoinduced desorption (PID) of N(2)O and CO from porous silicon (PSi) samples is reported. Both adsorbates exhibit unusually large cross sections for PID at 193 nm, up to 10(-15) cm(2), 2-3 orders of magnitude larger than the literature values for similar processes on flat Si. Under this UV irradiation, N(2)O molecules undergo photodissociation (a competing process leading to surface oxidation) with a cross section that is 2 orders of magnitude smaller than photodesorption. In the case of CO desorption is the exclusive photodepletion mechanism. PID efficiency decreases with increasing CO coverage suggesting PID hindrance by interactions among the desorbing CO molecules leading to re-adsorption at higher coverage. The wavelength and fluence dependence measurements exclude the possibility of laser induced thermal desorption for both adsorbates. The proposed mechanism for this phenomenon is desorption induced by hot electron transfer from the substrate to the adsorbate. Enhanced lifetime of transient negative adsorbate due to stabilization by localized holes on PSi nanotips can explain the observed abnormally large PID efficiency on top of porous silicon.

Enhanced Photochemistry of Ethyl Chloride on Ag Nanoparticles

“…and selectivity are possible. 5,19 Moreover, it has enabled us to study the effect of molecule−Ag NPs separation distance at subnanometer resolution for the first time, to the best of our knowledge. Alkyl halide surface photochemistry has been studied extensively.…”

“…To date, plasmon-induced photochemical experiments are usually performed in flow reactors − or in solution. − Sample preparation and characterization of such reactions under ultra-high vacuum (UHV) conditions eliminate the uncertainty regarding the effect of ligands, solvents, or other interacting chemicals. Under a clean and well-defined UHV environment, with in situ surface inspection before and following irradiation, detection of yields of reactivity and selectivity are possible. , Moreover, it has enabled us to study the effect of molecule–Ag NPs separation distance at subnanometer resolution for the first time, to the best of our knowledge.…”

Investigation the effect of porosity on corrosion of macroporous silicon in 1.0M sodium hydroxide solution using weight loss measurements, electrochemical methods and scanning electron microscope

“…Additionally, mainly used as an insulating layer in the silicon-on-insulator [8][9] , a sensing layer in biosensors [9] or chemical sensors [10] , an energy carrier [11] , a sacrificial layer in micromachining [12] , an important material for solar cell [13] and an excellent biomaterial in tissue engineering, tumor imaging and bioreactor platform drug delivery [3,7] . However, there are few works focusing on the applications of porous silicon in alkaline solution resulting from the corrosion and dissolution of porous silicon in these solutions [14][15][16] .…”

DFT Study of the Spin-Forbidden Reaction of N2O with CO Catalysed by Y+ Ions

“…The transition metal cations or transition metal oxide cations can provide fundamental information about catalytic action in different systems ranging from heterogeneous to homogeneous catalysis [5][6][7][8][9][10]. The reaction of oxygen transfer from N 2 O to CO can be catalysed by various transition metal cations in the gas phase and has been widely studied both experimentally and theoretically [11][12][13][14][15][16]. Recently, Böhme et al have paid particular attention to reaction (1) (energy of the reaction is -362.80 kJ mol -1 and activation energy barrier of the reaction is 197.60 kJ mol -1 [17]) catalysed by transition metal ions, which has been proposed as an efficient means of reducing the pollutant gases N 2 O and CO [18].…”