Since the first graphene gas sensor has been reported, functionalized graphene gas sensors have already attracted a lot of research interest due to their potential for high sensitivity, great selectivity, and fast detection of various gases. In this paper, we summarize the recent development and progression of functionalized graphene sensors for ammonia (NH₃) detection at room temperature. We review graphene gas sensors functionalized by different materials, including metallic nanoparticles, metal oxides, organic molecules, and conducting polymers. The various sensing mechanism of functionalized graphene gas sensors are explained and compared. Meanwhile, some existing challenges that may hinder the sensor mass production are discussed and several related solutions are proposed. Possible opportunities and perspective applications of the graphene NH₃ sensors are also presented.

Given the ubiquity of electronic devices and the urgent need to decrease our footprint in the context of global warming and planetary boundaries, it becomes critical to better quantify the environmental impacts of integrated circuit (IC) production. Our work addresses this question in three successive steps. First, we carry out a review of the data available since 2010 from four different literature categories, i.e., foundry reports, industry roadmaps, scientific literature, and life-cycle assessment databases. Then, we leverage the 27 identified sources to perform both a qualitative and quantitative analysis. We propose 10 features for characterizing the scope of studies while focusing on environmental indicators normalized per cm, i.e., energy consumption, carbon footprint and water consumption. The analysis results highlight a clear increasing trend of the environmental footprint with CMOS technology downscaling below 0.13 μm, despite a significant variation between the sources mainly due to scope mismatch. Finally, we show that environmental impacts per cm did not significantly decrease compared to historical values from 1980–2010, whereas the total silicon area produced keeps on increasing by 3.6%/year. Consequently, this work calls for urgently rethinking the road ahead with sobriety to effectively decrease the absolute environmental footprint of the IC production sub-sector.

Today, significant attention has been brought to the development of sensitive, specific, cheap, and reliable sensors for real-time monitoring. Molecular imprinting technology is a versatile and promising technology for practical applications in many areas, particularly chemical sensors. Here, we present a chemical sensor for detecting formaldehyde, a toxic common indoor pollutant gas. Polypyrrole-based molecularly-imprinted polymer (PPy-based MIP) is employed as the sensing recognition layer and synthesized on a titanium dioxide nanotube array (TiO₂-NTA) for increasing its surface-to-volume ratio, thereby improving the sensor performance. Our sensor selectively detects formaldehyde in the parts per million (ppm) range at room temperature. It also shows a long-term stability and small fluctuation to humidity variations. These are attributed to the thin fishnet-like structure of the PPy-based MIP on the highly-ordered and vertically-aligned TiO₂-NTA.

We report a new hybrid sensor in which an ultrathin polypyrrole (PPy) layer is deposited on the CVD-grown graphene (G) by electropolymerization. The sensor exhibits an excellent performance in the selective sensing of ammonia (NH ₃ ) at room temperature, having a high, fast, and reversible response. It also shows rather good stability, reproducibility, and immunity to humidity. These performances are attributed to the synergistic effect between the PPy layer and G. Specifically, the NH ₃ molecules are adsorbed on the PPy layer, electrons transfer from NH ₃ to the PPy layer, changing the PPy layer resistance. Electrons can also be transferred to the G through the ultrathin PPy layer, in certain way changing the G resistance. These promote the sensor sensitivity. Moreover, the ultrathin PPy layer with porous nature plays an important role in the sensor response, selectivity, and immunity to humidity. Graphene is not only a support material for PPy electropolymerization but also provides an efficient pathway for electron transfer, thereby, accelerating the sensor response and recovery. Our research indicates that the combination of PPy and G is a very promising as a chemical sensor material. We implement a smart prototype with the present sensor in an electronic board for real-time monitoring the NH ₃ concentrations. The smart prototype can be connected to a computer by a USB port for demonstrating NH ₃ concentrations, transmitting the data and analyzing the sensor response curves. Our results are beneficial forward the commercial design and fabrication of sensors fulfilling the specifications of practical applications.