Two-Dimensional Halide Perovskites: Approaches to Improve Optoelectronic Properties.

Three-dimensional (3D) halide perovskites (HPs) are in the spotlight of materials science research due to their excellent photonic and electronic properties suitable for functional device applications. However, the intrinsic instability of these materials stands as a hurdle in the way to their commercialization. Recently, two-dimensional (2D) HPs have emerged as an alternative to 3D perovskites, thanks to their excellent stability and tunable optoelectronic properties. Unlike 3D HPs, a library of 2D perovskites could be prepared by utilizing the unlimited number of organic cations since their formation is not within the boundary of the Goldschmidt tolerance factor. These materials have already proved their potential for applications such as solar cells, light-emitting diodes, transistors, photodetectors, photocatalysis, etc. However, poor charge carrier separation and transport efficiencies of 2D HPs are the bottlenecks resulting in inferior device performances compared to their 3D analogs. This minireview focuses on how to address these issues through the adoption of different strategies and improve the optoelectronic properties of 2D perovskites.

Mosquito-borne diseases in Assam, north-east India: current status and key challenges

Mosquito-borne diseases, including malaria, Japanese encephalitis (JE), lymphaticfilariasis and dengue, are major public health concerns in the north-easternstate of Assam, deterring equitable socioeconomic and industrial development.Among these, malaria and JE are the predominant infections and are spreadacross the state. The incidence of malaria is, however, gradually receding, witha consistent decline in cases over the past few years, although entry and spreadof artemisinin-resistant Plasmodium falciparum remains a real threat in thecountry. JE, formerly endemic in upper Assam, is currently spreading fast acrossthe state, with confirmed cases and a high case-fatality rate affecting all ages.Lymphatic filariasisis is prevalent but its distribution is confined to a few districtsand disease transmission is steadily declining. Dengue has recently invaded thestate, with a large concentration of cases in Guwahati city that are spreading tosuburban areas. Control of these diseases requires robust disease surveillanceand integrated vector management on a sustained basis, ensuring universalcoverage of evidence-based key interventions based on sound epidemiologicaldata. This paper aims to present a comprehensive review of the status of vectorborne diseases in Assam and to address the key challenges.

Dengue vectors in urban and suburban Assam, India: entomological observations

Background: Dengue is rapidly becoming established in north-east India andspreading, on account of rapid urbanization and population movement, withreported morbidity and attributable death cases. This study aims to determine theseasonal abundance of Aedes (Stegomyia) albopictus and Aedes (Stegomyia)aegypti in Guwahati metropolis and suburban settlements; to characterize thebreeding resources for these mosquitoes; and to ascertain the status of theirsusceptibility to adulticides and larvicides.Methods: Mosquito larval surveys were carried out in different localities in bothGuwahati city and adjoining suburbs from January to December 2013, to determinethe seasonal abundance of disease vectors and their breeding preferences.The insecticide susceptibility status of mosquito adults and larval populations ofboth Aedes aegypti and Aedes albopictus was ascertained, using World HealthOrganization standard diagnostic concentrations and test procedures.Results: The study revealed that both Aedes aegypti and Aedes albopictus arewidely abundant in Guwahati city and suburbs, and breeding in a wide variety ofresources. Aedes albopictus, however, was the predominant mosquito speciesin suburbs, breeding preferentially in flower vases, cut-bamboo stumps and leafaxils. Aedes aegypti was the most common in the city, breeding predominantly indiscarded tyres, cement tanks and used battery boxes. Both Aedes aegypti andAedes albopictus were resistant to dichlorodiphenyltrichloroethane (DDT; 4%), butsusceptible to malathion (5%), and exhibited a varied response to pyrethroids.However, larval populations of both these mosquito species were susceptible tolarvicides, including malathion (1.0 mg/L), temephos (0.02 mg/L) and fenthion(0.05 mg/L), at much lower dosages than diagnostic concentrations.Conclusion: Given the seasonal abundance and case incidence in city areas,it is highly probable that Aedes aegypti is the predominant mosquito vectortransmitting dengue virus. The study results have direct relevance for the statedengue-control programme, for targeting interventions and averting outbreaks andspread of disease