Loading uniform Ag_(3)PO_(4)nanoparticles on three-dimensional peony-like WO_(3)for good stability and excellent selectivity towards NH_(3)at room temperature

A heterojunction structure design is a very good method for improving the properties of semiconductors in many research fields.This method is employed in the present study to promote the gas-sensing performance of Ag_(3)PO_(4)nanocomposites at room temperature(25℃).A nanocomposite of Ag_(3)PO_(4)nanoparticles and three-dimensional peony-like WO_(3)(WO_(3)/Ag_(3)PO_(4))was successfully prepared by the precipitation method.The crystalline phases were analyzed by xray diffraction and the microstructure was characterized by scanning electron microscopy and transmission electron microscopy.The chemical bonding states were analyzed by x-ray photoelectron spectroscopy.The gas-sensing performance of WO_(3)/Ag_(3)PO_(4)sensors was systematically explored at room temperature.The composite sensors possessed a higher response and lower detection limit(1 ppm)to NH_(3)than those made of a single type of material;this is ascribed to the synergistic effect achieved by the heterojunction structure.Among the different composite sensors tested,gas sensor A5W5(Ag_(3)PO_(4):WO3mass ratio of 5:5)displayed the highest response to NH_(3)at room temperature.Interestingly,the A5W5 gas sensor exhibited relatively good stability and excellent selectivity to NH_(3).The A5W5 sensor also displayed a relatively good response under high humidity.The gas-sensing mechanism of the WO_(3)/Ag_(3)PO_(4)sensors is explained in detail.Taken together,the as-prepared sensor is highly efficient at detecting NH_(3)and could be suitable for practical applications.In addition,this study also provides a new method for developing Ag_(3)PO_(4)-based sensors in the gas-sensing field.

Mosquito larvicidal properties of volatile oil from salt marsh mangrove plant of Sesuvium portulacastrum against Anopheles stephensi and Aedes aegypti

Objective:To identify the larvicidal activity of the volatile oil from Sesuvium portulacastrum(S.portulacastrum)against Anopheles stephensi and Aedes aegypti.Methods:Volatile oil extract of S.portulacastrum was prepared in a graded series of concentration.The test for the larvicidal effect of volatile oil against mosquitos larvae was conducted in accordance with the WHO standard method.Batches of 25 early 4th instar larvae of two mosquitoes were transferred to 250 mL enamel bowl containing 199 mL of distilled water and 1 mL of plant extracts.Each experiment was conducted with triplicate with concurrent a control group.Results:Volatile oil extract of S.portulacastrum showed toxicity against 4th instar larvae of Aedes aegypti and Anopheles stephensi with equivalent LC50 value[(63±7.8)μL/mL,LCL-UCL=55.2-64.0]and LC90 value[(94.2±3.9)μL/mL]in maximum activity with minimum concentration(200μL/mL)of volatile oil and followed by maximum activity of 250μL concentration showed LC50 value=(68.0±8.2)μL/mL,LCL-UCL=66.26-69.2 and LC50 value of(55.2±2.8)μL/mL,LCL-UCL=53.7-56.9,LC90=(95.2±1.25)μL/mL and followed by 250μL of oil extract against 4th instar larvae of Aedes aegypti respectively.Conclusions:It is inferred from the present study that,the extracts from salt marsh mangrove plan of S.portulacastum are identified as a potential source of safe and efficacious mosquito control agents for the management of vector borne diseases of malaria and dengue.