Construction and Performance of a Nanocellulose–Graphene-Based Humidity Sensor with a Fast Response and Excellent Stability

Abstract

Humidity sensors have been widely applied in environmental monitoring, respiratory monitoring, electronic skin, noncontact switch, etc. However, weak interface interactions between a flexible substrate and conductive fillers will deteriorate the sensing performance. Herein, a flexible, rapid-response, and durable humidity sensor was proposed via employing cellulose nanofiber (CNF)-dispersed graphene (Gr) as a humidity sensing layer, which could be easily filtered onto a coessential CNF film (CNFF) to form the humidity sensor. CNFs as a dispersant and bonder strengthened the adhesion of graphene on the surface of the CNFF substrate. Simultaneously, CNFs as a reservoir provided abundant adsorption sites to capture water molecules and promoted electron transfer from adsorbed water molecules to graphene, further amplifying electrical signals by a hygroscopic expansion of the sensing layer under humidity conditions. Benefiting from this unique composition and structure, the prepared humidity sensor exhibited a rapid response (45 s) and recovery time (33 s), low hysteresis (4%), wide RH detection range (15−99%), and long-term stability (15 days). Further, the sensor could monitor the humidity of human skin and human breath, indicating a versatile noncontact humidity sensing function by altering its component proportion of CNF-to-Gr on demand.

Hybrid Water-Harvesting Channels Delivering Wide-Range and Supersensitive Passive Fluorescence Humidity Sensors

“…In addition, the humidity sensitivity of PFHS- 3 was proved to be durable in a consecutive “dry/wet” alternating process (7% RH/98% RH) over 10 cycles, which was supported by the nearly unchanged emission maximum values (Figure c). As shown in Figure d and Table S1, in terms of detection range and the lower limit, PFHS- 3 outperforms most previously reported moisture-sensitive materials, such as MXene, − semiconductor, ,− carbon, ,− fluorescent-based, − etc., which might be due to the enhanced water-harvesting and diffusing capabilities by the synergy of the hybrid channels.…”

Synergistic Applications of Graphene-Based Materials and Deep Eutectic Solvents in Sustainable Sensing: A Comprehensive Review

“…Recently, Yao et al proposed the construction of a sensor based on cellulose nanofiber (CNF)-dispersed graphene (Gr) as a humidity-sensing layer ( Figure 6 ) [ 102 ]. In this sensor, a DES (oxalic acid/betaine) was used as the solvent for the extraction of the CNFs from waste pulp.…”

“…The latter was filtered onto the coessential CNF film surface to form the sensor (②). Reprinted (adapted) with permission from the American Chemical Society [ 102 ].…”

Detection of gases and organic vapors by cellulose-based sensors

“…Cellulose nanofibers have also facilitated the fabrication of composites aimed at gas sensing with improved performance. For instance, composites based on cellulose nanofibers and carbon nanotubes [ 27 ] and graphene [ 28 ] have been reported for humidity sensing due to their hygroscopic nature. Furthermore, a sulfonic acid–cofunctionalized nanocellulose/graphene oxide membrane has been applied in an electrochemical gas sensor [ 29 ].…”