In recent years, sensing applications have played a very important role in various fields. As a novel natural material, cellulose-based membranes with many merits can be served as all kinds of sensors. This review summarizes the recent progress of cellulose membranes as sensors, mainly focusing on their preparation processes and sensing properties. In addition, the opportunities and challenges of cellulose membrane-based sensors are also prospected. This review provides some references for the design of cellulose membrane materials for sensing applications in the future.

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Recent advances in cellulose-based membranes for their sensing applications

Spinel MCo2O4 (M = Ni, Fe, Mn, Cu and Zn) demonstrates excellent physicochemical properties due to the combined effects of M2+ and Co3+ cations. Their inimitable optical, electronic, and mechanical properties open up windows for a broad range of promising applications. The development of novel spinels has opened virtually infinite possibilities for the development of different sensors. The association of nanomaterials with conventional electrodes or other substrates can produce completely novel and high performance sensors. The knowledge about the nanomaterials allows us to tailor sensors for desired applications. In this regard, the spinel MCo2O4 based materials and their composites offer great promise for the design and development of high-performance electrochemical sensors to detect target species in solution or in gas phase. Aiming to shed light on these important materials, this review presents the role of such cobaltites and their composites towards the development of electrochemical sensors with improved analytical properties for sensing in solution as well as gas phase. A critical comparison of the proposed sensors using these MCo2O4-based materials with other chemically-modified sensors considered the best choices in the literature for some target molecules is presented in order to demonstrate the benefits of such materials. Further, future perspectives and opportunities in these exciting research fields are also commented based on their current progress.

Feasible strategies to promote the sensing performances of spinel MCo2O4 (M = Ni, Fe, Mn, Cu and Zn) based electrochemical sensors: a review

Two-dimensional (2D) materials have shown great potential for gas sensing applications due to their large specific surface areas and strong surface activities. In addition to the commonly reported chemiresistive-type gas sensors, field-effect transistor (FET)-type gas sensors have attracted increased attention due to their miniaturized size, low power consumption, and good compatibility with CMOS technology. In this review, we aim to discuss the recent developments in chemiresistive- and FET-type gas sensors based on 2D materials, including graphene, transition metal dichalcogenides, MXenes, black phosphorene, and other layered materials. Firstly, the device structure and the corresponding fabrication process of the two types of sensors are given, and then the advantages and disadvantages are also discussed. Secondly, the effects of intrinsic and extrinsic factors on the sensing performance of 2D material-based chemiresistive and FET-type gas sensors are also detailed. Subsequently, the current gas-sensing applications of 2D material-based chemiresistive- and FET-type gas sensors are systematically presented. Finally, the future prospects of 2D materials in chemiresistive- and FET-type gas sensing applications as well as the current existing problems are pointed out, which could be helpful for the development of 2D material-based gas sensors with better sensing performance to meet the requirements for practical application.

A review on two-dimensional materials for chemiresistive- and FET-type gas sensors

In this work, we have grown ZnO/CuO nanoflowers on graphene printed paper substrates by the hydrothermal method. The hypothesis of the present work is the role of ZnO and CuO composited graphene structures as affordable substrates for room temperature ammonia gas sensor. To fabricate the conductive substrate, the biomass derived graphene has been formulated as conductive ink and printed (20 µm) on the paper substrate. The optical, structural, and morphological studies confirm the formation of hierarchical nanoflower like ZnO/CuO@graphene substrate. The chemiresistive gas sensor studies evident that, the ZnO/CuO@graphene substrates have higher sensing performance in the presence of ammonia (4.9%) for the concentration as low as 5 ppm at room temperature. It also shows a quick response and recovery time of 4.1 s and 2 s, respectively. Our present method will be an effective methodology for the fabrication of cost-effective and rapid detection of ammonia gas in the ambient environment and can be also further suitable for non-invasive earlier diagnosis of diseases from exhaled breath.

Selective room temperature ammonia gas sensor using nanostructured ZnO/CuO@graphene on paper substrate

In this work, we have grown ZnO/CuO nanoflowers on graphene printed paper substrates by the hydrothermal method. The hypothesis of the present work is the role of ZnO and CuO composited graphene structures as affordable substrates for room temperature ammonia gas sensor. To fabricate the conductive substrate, the biomass derived graphene has been formulated as conductive ink and printed (20 µm) on the paper substrate. The optical, structural, and morphological studies confirm the formation of hierarchical nanoflower like ZnO/CuO@graphene substrate. The chemiresistive gas sensor studies evident that, the ZnO/CuO@graphene substrates have higher sensing performance in the presence of ammonia (4.9%) for the concentration as low as 5 ppm at room temperature. It also shows a quick response and recovery time of 4.1 s and 2 s, respectively. Our present method will be an effective methodology for the fabrication of cost-effective and rapid detection of ammonia gas in the ambient environment and can be also further suitable for non-invasive earlier diagnosis of diseases from exhaled breath. • Hierarchical growth of ZnO/CuO nanoflowers on the graphene substrate. • Effective chemiresistive sensing performance of ammonia gas. • Sensing at lower ppm with higher response%. • Higher sensitivity and selectivity of ammonia gas sensing at ambient conditions. 

https://iopscience.iop.org/article/10.1149/1945-7111/ab77a0/pdf

S. Chandraleka

Papers

Review—Recent Advances in Electrochemical Impedance Spectroscopy Based Toxic Gas Sensors Using Semiconducting Metal Oxides

Highly Sensitive and Selective H 2 S Gas Sensor Fabricated with β-Ga 2 O 3 /rGO