Near-to-mid-infrared photodetection technologies could be widely deployed to advance the infrastructures of surveillance, environmental monitoring, and manufacturing, if the detection devices are low-cost, in compact format, and with high performance. For such application requirements, colloidal quantum dot (QD) based photodetectors stand out as particularly promising due to the solution processability and ease of integration with silicon technologies; unfortunately, the detectivity of the QD photodetectors toward longer wavelengths has so far been low. Here we overcome this performance bottleneck through synergistic efforts between synthetic chemistry and device engineering. First, we developed a fully automated aprotic solvent, gas-injection synthesis method that allows scalable fabrication of large sized HgTe QDs with high quality, exhibiting a record high photoluminescence quantum yield of 17% at the photoluminescence peak close to 2.1 μm. Second, through gating a phototransistor structure we demonstrate room-temperature device response to reach >2 × 10 cm Hz W (at 2 kHz modulation frequency) specific detectivity beyond the 2 μm wavelength range, which is comparable to commercial epitaxial-grown photodetectors. To demonstrate the practical application of the QD phototransistor, we incorporated the device in a carbon monoxide gas sensing system and demonstrated reliable measurement of gas concentration. This work represents an important step forward in commercializing QD-based infrared detection technologies.

MOF-based nanofiber filters via a scalable synthetic strategy serve a dual role in removing both PM2.5 and formaldehyde effectively.

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Quartz-enhanced photoacoustic spectroscopy (QEPAS) based on double acoustic microresonators (AmRs) is developed and experimentally investigated. The double AmR spectrophone configuration exhibits a strong acoustic coupling between the AmR and the quartz tuning fork, which results in a ∼5  ms fast response time. Moreover, the double AmRs provide two independent detection channels that allow optical signal addition or cancellation from different optical wavelengths and facilitate rapid multigas sensing measurements, thereby avoiding laser beam combination.

This paper reports the combustion and emission characteristics of the premixed MILD combustion of propane established by a single jet burner in a laboratory-scale cylindrical furnace. Measurements are made of spatial distributions of the furnace temperature and species concentrations (O2, CO2, CO, and NO) and also exhaust emissions of CO and NO. Experiments are conducted for different values of thermal input, injection diameter, and global equivalence ratio (Φ). Results are analyzed with the aids of computational fluid dynamics (CFD) simulations and chemical kinetic calculations, which use a simplified perfectly stirred reactor (PSR) system with exhaust gas recirculation (EGR). It is observed that the premixed MILD combustion of propane in the present furnace can be established once the injection momentum rate is sufficiently high to enable the flue gas recirculation rate K v > 2.5 (critical value) for Φ = 1.0. The critical K v increases as Φ falls. Inlet conditions of the transition regime should be avoided to prevent the occurrence of instability and flashback for this regime. The present premixed MILD combustion of propane generates low CO and NO emissions. At a sufficient residence time, an increased speed injection reduces NO emission mainly by growing K v and thus reducing the local peak temperature. In the present premixed MILD combustion, the prompt and reburning routes of NO formation are important. The effects of temperature, equivalence ratio, recirculation rate, and residence time should be systematically considered when optimizing the combustion system for ultralow NO emission.

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Fractal-shaped nanoantennas have a large potential to enable multiband devices for surface-enhanced spectroscopy due to their scale-invariant geometry that gives rise to strongly enhanced local fields across different spectral ranges with multiscale spatial distributions. In particular, fractal nanoantennas based on plasmonic metals are promising for biodetection applications that extend from the near-infrared across the mid-infrared spectrum. In this context, we introduce novel multiscale resonant structures based on the inverse Cesaro space-filling fractal curve with the remarkable property that the number of resonant bands does not depend on the overall size of the structures. We systematically study their scattering and near-field resonant properties by resorting to full-field finite difference time domain simulations in combination with experimental Fourier transform infrared microspectroscopy. In particular, by investigating a number of gold antennas fabricated by electron-beam lithography on CaF2 substrates, we demonstrate controllable multiband plasmonic resonances from near-infrared to the mid-infrared spectral regions. Moreover, our findings demonstrate that large values of near-field enhancement with hierarchical fractal distributions can be achieved in Cesaro-type nanoantennas across multiple bands that are ideally suited for chemical detection on a small footprint area. In order to demonstrate the full potential of Cesaro fractal nanoantennas for infrared sensing spectroscopy, we show triple band reliable detection of thin poly­(methyl methacrylate) layers with nanoscale thickness. The engineering of Cesaro-type plasmonic nanoantennas provides a novel strategy for the realization of active devices with a large spectral density and reduced footprints that can be conveniently integrated in future plasmonic–photonic active platforms for energy harvesting and optical biosensing.

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