colloidal quantum dots (cQDs) have been recently investigated as promising building blocks for low-cost and high-performance gas sensors due to their large effective surface-to-volume ratio and their suitability for versatile functionalization through surface chemistry. in this work we report on lead sulphide cQDs based sensors for room temperature no 2 detection. the sensor response has been measured for different pollutant gases including NO 2 , cH 4 , co and co 2 and for different concentrations in the 2.8-100 ppm range. For the first time, the influence of the QDs film thickness on the sensor response has been investigated and optimized. Upon 30 ppm NO 2 release, the best room temperature gas response is about 14 Ω/Ω, with response and recovery time of 12 s and 26 min, respectively. A detection limit of about 0.15 ppb was estimated from the slope of the sensor response and its electric noise. the gas sensors exhibit high sensitivity to no 2 , remarkable selectivity, repeatability and full recovery after exposure. Nitrogen dioxide (NO 2) is an important air pollutant since it contributes to the formation of the photochemical smog, the acid rains and it is also central to the formation of fine particles (PM) as well as affecting tropospheric ozone 1,2. Besides natural sources (volcanoes, oceans, biological decay, forest fires), a significant amount of NO 2 results from human activities such as combustion of fossil fuels welding, explosives, refining of petrol and metals, commercial manufacturing, and food manufacturing 3. These activities can generate high local concentration of NO 2 that produces significant impacts on human health, especially breathing problems since NO 2 inflames the lining of the lungs thus reducing immunity to lung infections 4,5. Therefore, reliable detection of NO 2 , even at low concentration, is critical in many different sectors such as industrial plants, indoor and outdoor air quality assurance, automotive and so on, and it is an enabling technology for automatic systems capable of taking necessary measures to reduce unsafe concentrations through ventilation, filtering or catalytic breakdown 6. At present, accurate measurement of air quality is possible only by means of large monitoring equipment or laboratory instruments, unsuitable for pervasive monitoring purposes. Alternative low-cost, small-size, ultralow-power gas sensor platforms have been developed during the last two decades, mainly in the form of components for experimental sensor networks, with promising superior performance in terms of sensitivity, selectivity, minimal drift, fast time response, compactness and low energy consumption 7,8. In particular, systems that meet the following characteristics would be of great interest: miniaturization and compatibility with the development of sensor arrays integration with temperature and humidity sensors, simple production techniques and process transferability towards innovative printing techniques. Today, commercially available gas sensors are mainly based on nanostructured me...

Semiconductor quantum dots have been recently employed as luminescent probes for the detection of hazardous nitroaromatic compounds. Despite the high sensitivity, such detection systems involve laboratory procedures and employ complex instrumentation. Here, we demonstrate the use of colloidal PbS quantum dots as the main component of a chemiresistor for the detection of nitroaromatic compounds. The proposed device is low-cost, reusable, and produces an electric signal that can be acquired with off-the-shelf electronic components. In this paper, we demonstrate the operation of the proposed device and we discuss its sensing mechanism. We also show the sensor's response to nitrobenzene in the 65 ppb−16 ppm range, estimating a theoretical detection limit of 2 ppb.

Detection of explosive traces in the vapor phase is of primary importance for safety and security in several environments. Different detection methods with high sensitivity are available in the market, but they are typically expensive and require specialized personnel to be operated. Here, we propose a compact, low-cost sensor for explosive detection based on the photoluminescence (PL) quenching of solid-state PbS quantum dot solids cast from the solution phase on a silicon substrate. We demonstrate the sensor capability to detect nitrobenzene vapor at a concentration as low as 445 ppb in air at room temperature, overcoming the performance of other state-of-the-art quantum dot-based PL sensors for nitroaromatic compounds. Moreover, the proposed system can be realized with off-the-shelf electronics and does not need any additional laboratory equipment to be operated, thus paving the way for its deployment in distributed sensor networks.

We report on a sensor architecture for detection of hazardous gases. The proposed device is based on the integration of a solid-state quantum dot (QD) photoluminescent probe with a QD photodetector on the same substrate. The effectiveness of the approach is demonstrated by developing a compact optical sensor for trace detection of explosives in air. The proposed architecture is very simple and consists of a silicon substrate with both surfaces coated with QD films. The upper layer acts as photoluminescent probe, pumped by a blue LED. The change of photoluminescence intensity associated to the interaction between the QDs and the target analyte is measured by the QD photodetector fabricated on the opposite side of the substrate. The sensor is mounted into a small chamber provided with the LED and the front-end electronics. The device is characterized by using nitrobenzene as representative nitroaromatic compound. Extremely low concentrations (down to 0.1ppm) can be detected by the proposed device, with a theoretical detection limit estimated to be as low as 2 ppb. Results are repeatable and no ageing effect is observed over a 70-day period. The proposed architecture may provide a promising solution for explosive detection in air as well as other sensing applications, thanks to its sensitivity, simple fabrication process, practical usability, and cost effectiveness.