Infrared (IR) cameras based on semiconductors grown by epitaxial methods face two main challenges, which are cost and operating at room temperature. The alternative new technologies which can tackle these two difficulties develop new and facile material and methods. Moreover, the implementation of high speed camera, which makes high resolution images with normal methods, is very expensive. In this paper, a new nanostructure based on a cost-effective solution processed technology for the implementation of the high-speed mid-infrared light camera at room temperature is proposed. To this end, the chemically synthesized PbSe–PbI2 core–shell Quantum Dots (QDs) are used. In this work, a camera including 10 × 10 pixels is fabricated and synthesized QDs spin-coated on interdigitated contact (IDC) and then the fabricated system passivated by epoxy resin. Finally, using an electronic reading circuit, all pixels are converted to an image on the monitor. To model the fabricated camera, we solved Schrodinger–Poisson equations self consistently. Then output current from each pixel is modeled based on semiconductor physics and dark and photocurrent, as well as Responsivity and Detectivity, are calculated. Then the fabricated device is examined, and dark and photocurrents are measured and compared to the theoretical results. The obtained results indicate that the obtained theoretical and measured experimental results are in good agreement together. The fabricated detector is high speed with a rise time of 100 ns. With this speed, we can get 10 million frames per second; this means we can get very high-resolution images. The speed of operation is examined experimentally using a chopper that modulates input light with 50, 100, 250, and 500 Hz. It is shown that the fabricated device operates well in these situations, and it is not limited by the speed of detector. Finally, for the demonstration of the proposed device operation, some pictures and movies taken by the camera are attached and inserted in the paper.
In this paper, a high-resolution full-color transparent monitor is designed and fabricated using the synthesized quantum dots for the first time. For this purpose, about 100 compounds that had the potential to emit blue, green, and red lights were selected, and simulation was performed using the discrete dipole approximation (DDA) method, in which the shell layer was selected to be SiO2 or TiO2 in the first step. Among the simulated compounds with SiO2 or TiO2 shells, Se/SiO2 and BTiO3/SiO2 were selected as blue light emitters with high intensity and narrow bandwidth. Accordingly, CdSe/SiO2 nanoparticles were selected as green light emitters and Au/TiO2 for the red light. As the surface of the nanoparticles in their optical properties is important, reactivation of the nanoparticles’ surface is required to reach the high-intensity peak and resolution. To this end, in the second step, the surface of Se and CdSe nanoparticles reacted with ethanolamine, which can make a strong bond with cadmium atoms. The band structure and optical properties were obtained by the density functional theory (DFT) method. The Se/Ethanolamine and CdSe/Ethanolamine were experimentally synthesized to evaluate the theoretical results, and their optical properties were measured. To fabricate a transparent monitor, Se/Ethanolamine, CdSe/SiO2, and Au/TiO2 nanoparticles were dispersed in polyvinyl alcohol (PVA) solved in water and deposited on the glass by the doctor blading technique. Finally, high-resolution videos and images were displayed on the fabricated monitor.
Multiphoton absorbing upconversion nanoparticles are emerging as bioimaging materials but are limited by the low quantum yield of their visible fluorescence. This article contains colloids of graphene quantum dots (GQDs), Neodymium, and Cobalt doped Graphene Quantum dots (Co-GQDs and Nd-GQDs) surrounded by carboxylic acids are synthesized which especially are suitable for bio applications; in this way, carboxylic acid groups exchanged by Amoxicillin as an antibiotic with bactericidal activity. The XRD diffraction method, TEM microscope, UV–Vis, and photoluminescence spectroscopies characterize the synthesized materials. The synthesized Quantum dots (QDs) exhibit upconversion properties and their emission is centered at 480 nm, but a red shift was observed with the increase of the excitation wavelength. In the emission spectra of synthesized QDs that can be related to the defect levels introduced by passivation of the QDs in the structure, the results show that with the interaction of the surface QDs with more carboxylic groups, the redshift is not observed. As the results indicate an increase in the intensity of upconversion emission is recorded for Co-GQDs and Nd-GQDs. The absolute quantum efficiency (QY) for Co-GQDs and Nd-GQDs were determined to be 41% and 100% more than GQDs respectively. DFT calculations indicate a strong bond between graphene and cobalt and Neodymium atoms. In doped materials, there are trap levels between the band gap of the GQDs which are responsible for increasing the intensity of the upconversion phenomenon.
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