Numerical study on the effect of nozzle-converging length on the aerosols collection efficiency and deposition on the impaction plate of a multi-nozzle inertial impactor.

Accurately locating deposited particles on the impaction plate of an inertial impactor is crucial for mineralogical and geochemical analysis. Since traditional methods relying on filter analysis are costly and time-consuming, this study delves into the numerical examination of the impact of nozzle-converging length (NCL) on the collection efficiency and depositional arrangements of various fine aerosol particles. Three distinct nozzle-converging lengths (NCL = 3, 7, and 13 mm) were simulated and rigorously compared for their performance in particle collection within an eight-nozzle inertial impactor PM 2.5 . Comprehensive analysis reveals that varying NCL does not significantly impact the collection efficiency of any investigated particle, with variations within 12% across all sizes in this study. Moreover, while NCL adjustments influence the settling ratio of primary depositions, these effects remain under 35% for all different-sized and shaped particles studied in this article. Furthermore, after examining 120 cases and averaging the collection efficiency for particles of a constant aerodynamic diameter, our findings indicate that the efficiency variations across the three distinct geometries remain under 5%. Consequently, we conclude that the head design of this impactor is independent from NCL. Notably, shorter NCLs result in denser particle accumulation near the nozzle outlet on the impaction plate, with this effect more pronounced for coarser particles. In summary, this research provides valuable insights into the role of nozzle-converging length in aerosol particle collection efficiency and deposition patterns, offering crucial guidance for particle classification and sampling methodologies eliminating the need for filter analysis.

Improved Dual-Polarity Response via Pyro-phototronic Effect for Filterless Visible Light Communication.

Dual-polarity response photodetectors (PDs) take full advantage of the directivity of the photocurrent to identify optical information. The dual-polarity signal ratio, a key parameter that represents the equilibrium degree of responses to different lights, is proposed for the first time. The synchronous enhancement of dual-polarity photocurrents and the amelioration of the dual-polarity signal ratio are beneficial to the practical applications. Herein, based on the selective light absorption and energy band structure design, a self-powered CdS/PEDOT:PSS/Au heterojunction PD consisting of a p-n junction and a Schottky junction exhibits unique wavelength-dependent dual-polarity response, where the photocurrent is negative and positive in the short and long wavelength regions, respectively. More importantly, the pyro-phototronic effect inside the CdS layer significantly improves the dual-polarity photocurrents with the maximum enhancement factors of 120%, 343%, 1167%, 1577%, and 1896% at 405, 450, 532, 650, and 808 nm, respectively. Furthermore, the dual-polarity signal ratio tends to 1:1 due to different degrees of the enhancement. This work provides a novel design strategy for dual-polarity response PDs with a simple working principle and improved performance, which can supply a substitution for two traditional PDs in the filterless visible light communication (VLC) system.

Self-Powered Filterless On-Chip Full-Stokes Polarimeter.

The detection of polarization states of light is essential in photonic and optoelectronic devices. Currently, the polarimeters are usually constructed with the help of waveplates or a comprehensive metasurface, which will inevitably increase the fabrication complexity and unnecessary energy loss. Here, we have successfully demonstrated a self-powered filterless on-chip full-Stokes polarimeter based on a single-layer MoS2/few-layer MoS2 homojunction. Combining the built-in electric field enhanced circular photogalvanic effect with the intrinsic optical anisotropy of MoS2 between in-plane and out-of-plane directions, the device is able to conveniently sense four Stokes parameters of incident light at zero bias without requiring an extra filtering layer and can function in the wavelength range of 650-690 nm with acceptable average errors. Besides, this homojunction device is easy to integrate with silicon-based chips and could have much smaller sizes than metasurface based polarimeters. Our study thus provides an excellent paradigm for high-performance on-chip filterless polarimeters.

Semi-outdoor filterless air purifier for smog and microbial protection with water purifier system.

PURPOSE: Air pollution and COVID-19 problems are being increasingly scrutinized. This article discusses the optimum design of an indoor and semi-outdoor air purifier, using a water-based filtration system. METHODS: An air purifier was fabricated, then comparison of purifying efficacy of the system between untreated air and using an air pump was done. Incense smoke was generated within a room for 10 seconds. The number of particle sizes of PM0.3, PM0.5, PM1.0, PM3.0, PM5.0, and PM10 µm (particle/ m3) as well as the detection of mass concentration of PM1.0, PM2.5, PM5.0, and PM10 (mg/m3) at 0 and 5 min were recorded. Each experiment was repeated 10 times. RESULTS: Particles in untreated air, except PM10, showed the maximum increase rate of the number of particle sizes greater than the air pump experiment. The highest differentiation between two methods was that PM1.0 and PM0.5 of untreated air increased to 113.647 and 61.539 % whereas the air pump method showed 4.720 and 2.533 %, respectively. The PM mass concentration of untreated air increased from 50.217 to 51.167 % while the increased rate of PM using an air pump was 2.784 to 2.902 %. CONCLUSION: This study proposed a water-based air filtration technique, which can reduce the level of particulate matter, and also is a low-cost prototype. For the next experiment, the study should extend test length, clarify an optimum ratio of disinfectant technologies, connect with the internet of things, compare the efficiency with a HEPA filter air purifier, and then also measure some particles which are smaller than 0.2 µm.

Filterless optical oxygen sensor based on a CMOS buried double junction photodiode.

We present a custom CMOS IC with a buried double junction (BDJ) photodiode to detect and process the optical signal, eliminating the need for any off-chip optical filters. The on-chip signal processing circuitry improves the desired signal extraction from the optical background noise. Since the IC is manufactured using standard commercial fabrication processes with no post-processing necessary, the system can ultimately be low cost to fabricate. Additionally, because of the CMOS integration, it will consume little power when operating, and even less during stand-by.

Monolithic Tandem Multicolor Image Sensor Based on Electrochromic Color-Radix Demultiplexing.

Optical data acquisition has been set as one of the milestones to testify the developments aimed at harnessing the full potential of the spatial and temporal data processing capabilities of the advanced semiconductor technology. A highly promising approach to drive the level of acquisition beyond the current technological node is the vertical integration of multiple photodetectors. However, vertical integration so far requires the same level of circuit complexity as lateral integration from the incapability of monolithic integration. Here, an electrochromic device architecture is introduced that enables realization of a monolithic tandem multicolor photodetector. The device, composed of vertically stacked p-type and n-type graphene barristors, is demonstrated to be capable of regulating the balanced charge transport under any desired illumination wavelengths. It exhibits variable anti-ambipolar charge transport behavior, which yields sensitive voltage-controlled photoconductive gain spectra. These electrical behaviors are utilized to fabricate an optoelectronic logic sensor that can demultiplex the desired color coordinate or wavelength in the constituent array with high color accuracy.

Highly Sensitive, Visible Blind, Wearable, and Omnidirectional Near-Infrared Photodetectors.

Visible blind near-infrared (NIR) photodetection is essential when it comes to weapons used by military personnel, narrow band detectors used in space navigation systems, medicine, and research studies. The technological field of filterless visible blind, NIR omnidirectional photodetection and wearability is at a preliminary stage. Here, we present a filterless and lightweight design for a visible blind and wearable NIR photodetector capable of harvesting light omnidirectionally. The filterless NIR photodetector comprises the integration of distinct features of lanthanide-doped upconversion nanoparticles (UCNPs), graphene, and micropyramidal poly(dimethylsiloxane) (PDMS) film. The lanthanide-doped UCNPs are designed such that the maximum narrow band detection of NIR is easily accomplished by the photodetector even in the presence of visible light sources. Especially, the 4f n electronic configuration of lanthanide dopant ions provides for a multilevel hierarchical energy system that provides for longer lifetime of the excited states for photogenerated charge carriers to transfer to the graphene layer. The graphene layer can serve as an outstanding conduction path for photogenerated charge carrier transfer from UCNPs, and the flexible micropyramidal PDMS substrate provides an excellent platform for omnidirectional NIR light detection. Owing to these advantages, a photoresponsivity of ∼800 AW-1 is achieved by the NIR photodetector, which is higher than the values ever reported by UCNPs-based photodetectors. In addition, the photodetector is stretchable, durable, and transparent, making it suitable for next-generation wearable optoelectronic devices.