MSc Fei Wang

1. Hollow 3D PANI@ PSS-rGO microspheres enabling ultra-sensitive room temperature ammonia gas sensing
   Hongping Liang; Zilun Tang; Zhuo Chen; Zhenting Zhao; Min Zeng; Weiping Gong; Fei Wang; Patrick J French; Quan Wang; Hao Li; Guofu Zhou; Yao Wang;
   Sensors and Actuators B,
   Volume 460, Issue 139955, 2026. DOI: https://doi-org.tudelft.idm.oclc.org/10.1016/j.snb.2026.1399
   
   Keywords: ...

   Hollow sphere Graphene Polyaniline Ammonia sensing Room temperature.
   
   
   Abstract: ...

   Designing sensing materials with distinct morphologies remains a key challenge in the development of high-performance gas-sensing devices. In this study, we employed a supramolecular assembly and ice-melting-induced lyophilization (IMIL) technique to synthesize poly (sodium p-styrenesulfonate)-functionalized reduced graphene oxide (PSS-rGO) microspheres. We then used in situ chemical oxidation polymerization to create a hollow three-dimensional (3D) polyaniline-decorated PSS-rGO microspheres (PANI@PSS-rGO) and conducted a trace analysis of ammonia (NH3) at room temperature. The PANI was uniformly decorated on the surfaces of the PSS-rGO microspheres, and the PANI@PSS-rGO exhibited a hollow microsphere morphology. This structure’s large specific surface area provided sufficient adsorption sites and enabled fast multichannel charge transfer. The hollow 3D PANI@PSS-rGO composite had ultra-high sensitivity of 7.06% / ppm at high concentrations and 55.86% / ppm at low concentrations, as well as short response and recovery times of 9 and 120 s, respectively. We attributed the good selectivity, repeatability, and long-term stability of the PANI@PSS-rGO composite to the significant synergistic effect of the PANI and the PSS-rGO. We determined a promising route to room-temperature gas sensors for ultrasensitive trace analysis of NH3, which is enabled by this 3D framework.

2. Pixel Optimizations and Digital Calibration Methods of a CMOS Image Sensor Targeting High Linearity
   Fei Wang; Albert Theuwissen;
   IEEE Transactions on Circuits and Systems I: Regular Papers,
   Volume 66, Issue 3, pp. 930--940, March 2019. DOI: 10.1109/tcsi.2018.2872627
   
   Abstract: ...

   In this paper, different methodologies are employed to improve the linearity performance of a prototype CMOS image sensor (CIS). First, several pixel structures, including a novel pixel design based on a capacitive trans-impedance amplifier (CTIA), are proposed to achieve a higher pixel-level linearity. Furthermore, three types of digital linearity calibration methods are explored. A prototype image sensor designed in 0.18-μm, 1-poly, and 4-metal CIS technology with a pixel array of 128×160 is used to verify these linearity improvement techniques. The measurement results show that the proposed CTIA pixel has the best linearity result out of all pixel structures. Meanwhile, the proposed calibration methods further improved the linearity of the CIS without changing the pixel structure. The pixel mode method achieves the most significant improvement on the linearity. One type of 4T pixel attains a nonlinearity of 0.028% with pixel mode calibration, which is two times better than the state of the art. Voltage mode (VM) and current mode (CM) calibration methods get rid of the limitation on the illumination condition during calibration operation; especially, CM calibration can further suppress the nonlinearity caused by the integration capacitor C FD on the floating diffusion node, which is remnant in VM.

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