Infrared multispectral imaging is attracting great interest with the increasing demand for sensitive, low-cost and scalable devices that can distinguish coincident spectral information. However, the ...widespread use of such detectors is still limited by the high cost of epitaxial semiconductors. In contrast, the solution processability and wide spectral tunability of colloidal quantum dots (CQDs) have inspired various inexpensive, high-performance optoelectronic devices. Here, we demonstrate a two-terminal CQD dual-band detector, which provides a bias-switchable spectral response in two distinct bands. A vertical stack of two rectifying junctions in a back-to-back diode configuration is created by engineering a strong and spatially stable doping process. By controlling the bias polarity and magnitude, the detector can be rapidly switched between short-wave infrared and mid-wave infrared at modulation frequencies up to 100 kHz with D* above 1010 jones at cryogenic temperature. The detector performance is illustrated by dual-band infrared imaging and remote temperature monitoring.Colloidal quantum dot detectors, switchable between short-wave infrared and mid-wave infrared, are demonstrated.
Improving charge mobility in quantum dot (QD) films is important for the performance of photodetectors, solar cells and light-emitting diodes. However, these applications also require preservation of ...well defined QD electronic states and optical transitions. Here, we present HgTe QD films that show high mobility for charges transported through discrete QD states. A hybrid surface passivation process efficiently eliminates surface states, provides tunable air-stable n and p doping and enables hysteresis-free filling of QD states evidenced by strong conductance modulation. QD films dried at room temperature without any post-treatments exhibit mobility up to μ ~ 8 cm
V
s
at a low carrier density of less than one electron per QD, band-like behaviour down to 77 K, and similar drift and Hall mobilities at all temperatures. This unprecedented set of electronic properties raises important questions about the delocalization and hopping mechanisms for transport in QD solids, and introduces opportunities for improving QD technologies.
Colloidal quantum dots (CQDs) have unique advantages in the wide tunability of visible-to-infrared emission wavelength and low-cost solution processibility ...
In addition to the kidney, the intestine is one of the most important organs involved in uric acid excretion. However, the mechanism of urate excretion in the intestine remains unclear. Therefore, ...the relationship between soluble uric acid and the gut excretion in human intestinal cells was explored. The relevant signaling molecules were then also examined.
HT-29 and Caco-2 cell lines were stimulated with soluble uric acid. Western blotting and qRT-PCR were used to measure protein and mRNA levels. Subcellular fractionation methods and immunofluorescence were used to quantify the proteins in different subcellular compartments. Flow cytometry experiments examined the function of ATP-binding cassette transporter, subfamily G, member 2 (ABCG2). Small interfering RNA transfection was used to assess the interaction between ABCG2 and PDZ domain-containing 1 (PDZK1).
Soluble uric acid increased the expression of PDZK1 and ABCG2. The stimulation of soluble uric acid also facilitated the translocation of ABCG2 from the intracellular compartment to the plasma membrane and increased its transport activity. Moreover, the upregulation of PDZK1 and ABCG2 by soluble uric acid was partially decreased by either TLR4-NLRP3 inflammasome inhibitors or PI3K/Akt signaling inhibitors. Furthermore, PDZK1 knockdown significantly inhibited the expression and transport activity of ABCG2 regardless of the activation by soluble uric acid, demonstrating a pivotal role for PDZK1 in the regulation of ABCG2.
These findings suggest that urate upregulates the expression of PDZK1 and ABCG2 for excretion in intestinal cells via activating the TLR4-NLRP3 inflammasome and PI3K/Akt signaling pathway.
Due to thermal carriers generated by a narrow mid-infrared energy gap, cooling is always necessary to achieve ideal photodetection. In quantum dot (QD), the electron thermal generation should be ...reduced with quantum confinement in all three dimensions. As a result, there would be a great potential to realize high-operating-temperature (HOT) QD mid-IR photodetectors, though not yet achieved. Taking the advantages of colloidal nanocrystals' solution processability and precise doping control by surface dipoles, this work demonstrates a HOT mid-infrared photodetector with a QD gradient homojunction. The detector achieves background-limited performance with D
= 2.7 × 10
Jones on 4.2 μm at 80 K, above 10
Jones until 200 K, above 10
Jones until 280 K, and 7.6 × 10
Jones on 3.5 μm at 300 K. The external quantum efficiency also achieves more than 77% with responsivity 2.7 A/W at zero bias. The applications such as spectrometers, chemical sensors, and thermal cameras, are also approved, which motivate interest in low-cost, solution-processed and high-performance mid-infrared photodetection beyond epitaxial growth bulk photodetectors.
The infrared technology is entering widespread use as it starts fulfilling a growing number of emerging applications, such as smart buildings and automotive sectors. Majority of infrared ...photodetectors are based on interband transition, which is the energy gap between the valence band and the conduction band. As a result, infrared materials are mainly limited to semi-metal or ternary alloys with narrow-bandgap bulk semiconductors, whose fabrication is complex and expensive. Different from interband transition, intraband transition utilizing the energy gap inside the band allows for a wider choice of materials. In this paper, we mainly discuss the recent developments on intraband infrared photodetectors, including 'bottom to up' devices such as quantum well devices based on the molecular beam epitaxial approach, as well as 'up to bottom' devices such as colloidal quantum dot devices based on the chemical synthesis.
Colloidal quantum dots (CQDs) are of interest for optoelectronic devices because of the possibility of high-throughput solution processing and the wide energy gap tunability from ultraviolet to ...infrared wavelengths. People may question about the upper limit on the CQD wavelength region. To date, although the CQD absorption already reaches terahertz, the practical photodetection wavelength is limited within mid-wave infrared. To figure out challenges on CQD photoresponse in longer wavelength, would reveal the ultimate property on these nanomaterials. What's more, it motivates interest in bottom-up infrared photodetection with less than 10% cost compared with epitaxial growth semiconductor bulk. In this work, developing a re-growth method and ionic doping modification, we demonstrate photodetection up to 18 μm wavelength on HgTe CQD. At liquid nitrogen temperature, the responsivity reaches 0.3 A/W and 0.13 A/W, with specific detectivity 6.6 × 10
Jones and 2.3 × 10
Jones for 18 μm and 10 μm CQD photoconductors, respectively. This work is a step toward answering the general question on the CQD photodetection wavelength limitation.
In this work, the influence of the terminating or exposed crystal planes of anatase TiO2 support on the catalytic activity of Pt/TiO2 catalysts is reported. Strong effects were observed when using CO ...oxidation as a probe reaction. The CO oxidation activity over these catalysts ranks in the following order: Pt/TiO2-{101} > Pt/TiO2-{100} > Pt/TiO2-{001}. The combination of in situ X-ray absorption spectroscopy, X-ray emission spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory calculations unravelled a strong interaction between platinum particles and different dominating facets of anatase. The catalytic activity of the Pt/TiO2 catalysts can be correlated with the spectroscopic/structural results. Compared to {001} facets, the {100} and {101} facets of TiO2 can stabilize active highly dispersed Pt species and avoid sintering Pt particles. This finding provides some important insights into understanding the metal–support interfacial interactions of Pt/TiO2 catalysts for tuning their catalytic performance.
Spectral analysis is an important tool that is widely used in scientific research and industry. Although the performance of benchtop spectrometers is very high, miniaturization and portability are ...more important indicators in some applications, such as on-site detection and real-time monitoring. Since the 1990s, micro spectrometers have emerged and developed. Meanwhile, with the development of nanotechnology, nanomaterials have been applied in the design of various micro spectrometers in recent years, further reducing the size of the spectrometers. In this paper, we review the research progress of micro spectrometers based on nanomaterials. We also discuss the main limitations and perspectives on micro spectrometers.
Quantum dot materials, with their unique photophysical properties, are promising zero-dimensional materials for encryption, display, solar cells, and biomedical applications. However, due to the ...large surface to volume ratio, they face the challenge of chemical instability and low carrier transport efficiency, which have greatly limited their reliability and utility. In light of the current development bottleneck of quantum dot materials, the chemical stability and physical properties can be effectively improved by the self-assembly method. This review will discuss the research progress of the self-assembly methods of quantum dots and analyze the advantages and disadvantages of those self-assembly methods. Furthermore, the scientific challenges and improvement in the self-assembly method of quantum dots are prospected.
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