Publications

Single walled carbon nanotubes has been identified as a potential material for CO2 gas sensing, capture and storage, however, comprehensive understanding of adsorption/desorption mechanisms that drives these application is still lacking yet such knowledge is essential for mainstream application of SWCNT in the identified areas. In this work, we use Density Functional Theory to study CO2 storage and sensing on SWCNTs with the aim of unraveling how such applications can be enhanced with the introduction of dopants with emphasis on Al, B, N and S as potential dopants. It is observed that doping SWCNT with N and B can be easily achieved compared to Al and S, which reported high and positive formation energies thus, can only be achieved under non-equilibrium condition. N doping improves SWCNT interaction with CO2 molecules and when subjected to thermal treatment the adsorbed CO2 is release to the atmosphere at 423 K thus a reusable sensing element can be achieved. It was further observed that the diffusion of molecular CO2 within the proximity of Al and S dopants in SWCNT matrix is not favored, while N and B doped SWCNT tend to have lower barrier energies to CO2, thus can offer better control of carbon storage. Our finding can assist in the design and optimization of SWCNT for energy and environmental applications.

ZnO nanowires have been proposed as potential photo-anode materials for photo-electrochemical water splitting due to their low toxicity, simple synthesis and easy modification routes. However, ZnO suffers from low PEC activity and photo-corrosion eff ;ects, and therefore, application of ZnO nanowires in PEC water splitting still awaits development of effective design and synthesis strategies to improve its PEC efficiencies to commercially viable levels. Here, we present ab initio Density Functional Theory calculations considering 3d transition metal doping as a potential route towards attainment of ZnO nanowires with superior PEC activity. Our results show that the stability of 3d transition metal dopants in ZnO NWs is dependent on the d character of the transition metal dopant as well as their concentration and doping site, with most transition metal atoms being energetically most favorable at the Zn substitutional site both in O-rich and Zn-rich conditions considered. Specifically, we find all 3d transition metal dopants in ZnO NW under O-rich conditions as well as Sc, Ti and V under Zn-rich conditions have negative formation energies at the considered dopant concentrations of 1−6 atm. %, indicating that these dopants can readily be incorporated into ZnO NWs at thermodynamic equilibrium conditions. The electronic properties of Ti and V at 2% and 4% dopant concentration, respectively, yield a staggered band-structure configuration, while Sc, Cr, Mn, Co, Ni, and Cu dopants in ZnO NWs induce band-edge states. In addition, 3d TM dopants induces significant red-shift of the absorption edge of ZnO NW due to reduction in band gap, and are projected to improve visual light harvesting capabilities. Finally, the band alignment relative to the redox potential of water revealed that the valence band maximum of Sc, V, Ni and Cu doped ZnO NWs remains strongly positive above the oxidation potential of O2/H2O, while their reduction potential remain negative below the reduction potential of H+/H2, favouring PEC applications.

Purpose Street-connected youth (SCY) in Kenya and elsewhere in sub–Saharan Africa are at high risk of HIV. Voluntary Male Medical Circumcision (VMMC) reduces the risk of female-to-male HIV transmission. Circumcision is also a traditional coming-of-age process in many Kenyan ethnic groups. This paper describes the acceptability of VMMC delivered as part of a ten-day healing, educational, and ‘coming-of-age’ retreat implemented as a pilot with SCY. Methods Male SCY aged between 12 and 24 living on the street for more than 3 months were eligible to participate. The study took place over 10 days. After medical circumcision, youth participated in education modules. Data collected included qualitative semi-structured exit interviews featuring structured and open-ended questions about factors relevant to this intervention's acceptability. Results There were 116 SCY (median age 14, IQR 13–15) who participated in the study. All were circumcised successfully, with no major complications. The majority of participants (81%) agreed that the circumcision procedure was uncomplicated, and 99% agreed the education was an important part of the initiation process. Thematic analysis of interview data highlighted four factors important to the program's acceptability: providing food, shelter, security; providing a safe place to heal; including traditional elements; and being with peers. Conclusions This novel implementation of VMMC was found to be acceptable to SCY participants and could likely be adapted and scaled for HIV prevention and education with SCY elsewhere in Kenya and sub–Saharan Africa where circumcision is part of traditional coming-of-age processes.