This study reports on the mid-infrared (mid-IR) photothermal response of multilayer MoS2 thin films grown on crystalline (p-type silicon and c-axis- oriented single crystal sapphire) and amorphous (Si/SiO2 and Si...This study reports on the mid-infrared (mid-IR) photothermal response of multilayer MoS2 thin films grown on crystalline (p-type silicon and c-axis- oriented single crystal sapphire) and amorphous (Si/SiO2 and Si/SiN) substrates by pulsed laser deposition (PLD). The photothermal response of the MoS2 films is measured as the changes in the resistance of the MoS2 films when irradiated with a mid-IR (7 to 8.2 μm) source. We show that enhancing the temperature coefficient of resistance (TCR) of the MoS2 thin films is possible by controlling the film-substrate interface through a proper choice of substrate and growth conditions. The thin films grown by PLD are characterized using X-ray diffraction, Raman, atomic force microscopy, X-ray photoelectron microscopy, and transmission electron microscopy. The high-resolution transmission electron microscopy (HRTEM) images show that the MoS2 films grow on sapphire substrates in a layer-by-layer manner with misfit dislocations. The layer growth morphology is disrupted when the films are grown on substrates with a diamond cubic structure (e.g., silicon) because of twin growth formation. The growth morphology on amorphous substrates, such as Si/SiO2 or Si/SiN, is very different. The PLD-grown MoS2 films on silicon show higher TCR (-2.9% K^-1 at 296 K), higher mid-IR sensitivity (△R/R = 5.2%), and higher responsivity (8.7 V·W^-1) compared to both the PLD-grown films on other substrates and the mechanically exfoliated MoS2 flakes transferred to different substrates.展开更多
The aim of this research was to investigate the luminescent behavior of ultra-small Eu3+-activated phosphate and vanadate nanoparticles in the presence of pesticides.Nanoparticles have an average diameter of approxima...The aim of this research was to investigate the luminescent behavior of ultra-small Eu3+-activated phosphate and vanadate nanoparticles in the presence of pesticides.Nanoparticles have an average diameter of approximately 2 nm with a narrow size distribution.The monazite crystal structure of phosphate-based particles(space group P121/n1)and single tetragonal zircon-type structure of vanadate-based particles(space group of I41/amd)have been confirmed using X-ray diffraction measurements.All synthesized Eu3+-activated colloidal nanoparticles show sharp emission peaks in the red spectral region.Photoluminescence measurements revealed emission quenching upon addition of millimolar concentrations of following pesticides:4-Chloro-2-methyl-phenoxyacetic acid(MCPA),2,4-Dichlorophenoxyacetic acid(2,4-D)and N-(phosphonomethyl)glycine(Glyphosate).In both phosphate and vanadate-based colloidal nanoparticles luminescence quenching is more evident in the presence of 2,4-D pesticide with the lowest limit of detection(0.7μM)obtained for phosphate-based nanoparticles.展开更多
文摘This study reports on the mid-infrared (mid-IR) photothermal response of multilayer MoS2 thin films grown on crystalline (p-type silicon and c-axis- oriented single crystal sapphire) and amorphous (Si/SiO2 and Si/SiN) substrates by pulsed laser deposition (PLD). The photothermal response of the MoS2 films is measured as the changes in the resistance of the MoS2 films when irradiated with a mid-IR (7 to 8.2 μm) source. We show that enhancing the temperature coefficient of resistance (TCR) of the MoS2 thin films is possible by controlling the film-substrate interface through a proper choice of substrate and growth conditions. The thin films grown by PLD are characterized using X-ray diffraction, Raman, atomic force microscopy, X-ray photoelectron microscopy, and transmission electron microscopy. The high-resolution transmission electron microscopy (HRTEM) images show that the MoS2 films grow on sapphire substrates in a layer-by-layer manner with misfit dislocations. The layer growth morphology is disrupted when the films are grown on substrates with a diamond cubic structure (e.g., silicon) because of twin growth formation. The growth morphology on amorphous substrates, such as Si/SiO2 or Si/SiN, is very different. The PLD-grown MoS2 films on silicon show higher TCR (-2.9% K^-1 at 296 K), higher mid-IR sensitivity (△R/R = 5.2%), and higher responsivity (8.7 V·W^-1) compared to both the PLD-grown films on other substrates and the mechanically exfoliated MoS2 flakes transferred to different substrates.
基金support from the National Recruitment Program of High-end Foreign Experts(Grant No.GDT20185200479)offered by the Chongqing University of Posts and Telecommunications(CQUPT),Chinafinancial support of the Ministry of Education,Science and Technological Development of the Republic of Serbia(Nos.45020 and 172056).
文摘The aim of this research was to investigate the luminescent behavior of ultra-small Eu3+-activated phosphate and vanadate nanoparticles in the presence of pesticides.Nanoparticles have an average diameter of approximately 2 nm with a narrow size distribution.The monazite crystal structure of phosphate-based particles(space group P121/n1)and single tetragonal zircon-type structure of vanadate-based particles(space group of I41/amd)have been confirmed using X-ray diffraction measurements.All synthesized Eu3+-activated colloidal nanoparticles show sharp emission peaks in the red spectral region.Photoluminescence measurements revealed emission quenching upon addition of millimolar concentrations of following pesticides:4-Chloro-2-methyl-phenoxyacetic acid(MCPA),2,4-Dichlorophenoxyacetic acid(2,4-D)and N-(phosphonomethyl)glycine(Glyphosate).In both phosphate and vanadate-based colloidal nanoparticles luminescence quenching is more evident in the presence of 2,4-D pesticide with the lowest limit of detection(0.7μM)obtained for phosphate-based nanoparticles.