The Frontiers of Functionalized Nanocellulose-Based Composites and Their Application as Chemical Sensors.

Chemical sensors are a rapidly developing technology that has received much attention in diverse industries such as military, medicine, environmental surveillance, automotive power and mobility, food manufacturing, infrastructure construction, product packaging and many more. The mass production of low-cost devices and components for use as chemical sensors is a major driving force for improvements in each of these industries. Recently, studies have found that using renewable and eco-friendly materials would be advantageous for both manufacturers and consumers. Thus, nanotechnology has led to the investigation of nanocellulose, an emerging and desirable bio-material for use as a chemical sensor. The inherent properties of nanocellulose, its high tensile strength, large specific surface area and good porous structure have many advantages in its use as a composite material for chemical sensors, intended to decrease response time by minimizing barriers to mass transport between an analyte and the immobilized indicator in the sensor. Besides which, the piezoelectric effect from aligned fibers in nanocellulose composites is beneficial for application in chemical sensors. Therefore, this review presents a discussion on recent progress and achievements made in the area of nanocellulose composites for chemical sensing applications. Important aspects regarding the preparation of nanocellulose composites using different functionalization with other compounds are also critically discussed in this review.

Fabrication of a Nickel Ferrite/Nanocellulose-Based Nanocomposite as an Active Sensing Material for the Detection of Chlorine Gas.

Chlorine gas is extensively utilised in industries as both a disinfectant and for wastewater treatment. It has a pungent and irritating odour that is comparable with that of bleach and can cause serious health issues such as headaches and breathing difficulties. Hence, efficiently, and accurately monitoring chlorine gas is critical to ensure that no undesirable incidents occur. Due to its remarkable characteristics, numerous researchers have explored the potential of ferrite nanoparticles as a sensing material for chlorine gas detection. Among several ferrite nanoparticles, nickel ferrite (NiFe2O4) is extensively studied as an inverse spinel structured magnetic material that may be ideal for sensing applications. However, the magnetic characteristics of NiFe2O4 cause agglomeration, which necessitates the use of a substrate for stabilisation. Therefore, nanocellulose (NC), as a green and eco-friendly substrate, is ideal for stabilising bare nickel ferrite nanoparticles. In a novel experiment, nickel ferrite was loaded onto NC as a substrate using in situ deposition. The structure was confirmed by X-ray Diffraction (XRD) analysis, while elemental composition was verified by Energy dispersive X-ray (EDX) analysis. Gas sensing properties were determined by evaluating sensitivity as a function of various regulating factors, such as the amount of nickel ferrite, gas concentration, repeatability, and reusability. In the evaluation, 0.3 g nickel ferrite showed superior response and sensitivity than those of other samples. The achieved response time was around 40 s, while recovery time was about 50 s. This study demonstrates the potential of a nickel ferrite/nanocellulose-based nanocomposite to efficiently monitor chlorine gas.

Characterizations of MWCNTs Nanofluids on the Effect of Surface Oxidative Treatments.

In this study, multi-walled carbon nanotubes (MWCNTs) were chemically modified using three acid treatment methods to introduce the surface oxygen functional group (SOFG). The presence of SOFG on the MWCNTs has been characterized by Fourier Transform Infrared (FTIR) spectroscopy. Morphology, structural and thermal properties were performed using Field Emission Scanning Electron Microscopy (FESEM), Raman spectroscopy, and Thermogravimetric analysis (TGA), respectively. The result shows that the modification with acid treatment significantly affects the degree of defects and surface group functionality of surface oxidized MWCNTs from method B. The preparation of nanofluids using MWCNTs produced from method B (MWCNT-MB) was prepared using two different parameters: with and without polyvinylpyrrolidone (PVP) as surfactant. The experiment was conducted by setting variable carbon particle concentration from 0.1 wt.% to 1.0 wt.%, and the amount of PVP is 10% of carbon particles at different temperatures (6 °C, 25 °C, 40 °C). Based on visual observation, the dispersion of carbon particles was enhanced by the presence of PVP as the stabilizing agent. The thermal conductivity performance of nanofluids revealed that the surface oxidized MWCNTs with PVP show enhanced thermal conductivity compared to the nanofluid containing MWCNTs without PVP. The improvement contributes to this in terms of stability and homogenization of nanoparticles. Hence the improved distribution of MWCNTs in water-based media improves thermal conductivity. These promising properties of MWCNTs in water-based fluids would enable the nanofluids to be used in heat transfer fluid and cooling applications.