Vijay K. Tomer

Cubic mesoporous Ag@CN: a high performance humidity sensor

The fabrication of highly responsive, rapid response/recovery and durable relative humidity (%RH) sensors that can precisely monitor humidity levels still remains a considerable challenge for realizing the next generation humidity sensing applications. Herein, we report a remarkably sensitive and rapid %RH sensor having a reversible response using a nanocasting route for synthesizing mesoporous g-CN (commonly known as g-C3N4). The 3D replicated cubic mesostructure provides a high surface area thereby increasing the adsorption, transmission of charge carriers and desorption of water molecules across the sensor surfaces. Owing to its unique structure, the mesoporous g-CN functionalized with well dispersed catalytic Ag nanoparticles exhibits excellent sensitivity in the 11-98% RH range while retaining high stability, negligible hysteresis and superior real time %RH detection performances. Compared to conventional resistive sensors based on metal oxides, a rapid response time (3 s) and recovery time (1.4 s) were observed in the 11-98% RH range. Such impressive features originate from the planar morphology of g-CN as well as unique physical affinity and favourable electronic band positions of this material that facilitate water adsorption and charge transportation. Mesoporous g-CN with Ag nanoparticles is demonstrated to provide an effective strategy in designing high performance %RH sensors and show great promise for utilization of mesoporous 2D layered materials in the Internet of Things and next generation humidity sensing applications.

An excellent humidity sensor based on In–SnO2 loaded mesoporous graphitic carbon nitride

A highly sensitive and fast responsive relative humidity (% RH) sensor based on In–SnO2 loaded cubic mesoporous graphitic carbon nitride (g-C3N4) has been demonstrated in this study. The mesoporous In–SnO2/meso-CN nanohybrid was synthesized through template inversion of mesoporous silica, KIT-6, using a nanocasting process. Due to its 3D replicated cubic structure with ordered mesopores, the nanohybrid facilitates the process of adsorption, charge transmission and desorption of water molecules across the sensor surfaces. Consequently, the optimized In–SnO2/meso-CN nanohybrid exhibits excellent response (5 orders change in impedance) in the 11–98% RH range, high stability, negligible hysteresis (0.7%) and superior real time % RH detection performance. Compared to traditional metal oxide based resistive sensors with unique mesoporous/hierarchical/sheet-like morphology, the 3D mesostructured In–SnO2/meso-CN nanohybrid demonstrated a superfast response (3.5 s) and recovery (1.5 s) in the 11–98% RH range at room temperature. These results open the door for breath monitoring and show a promising glimpse for designing mesoporous 2D layered materials in the development of future ultra-sensitive % RH sensors.

Near-Room-Temperature Ethanol Detection Using Ag-Loaded Mesoporous Carbon Nitrides

Development of room-temperature gas sensors is a much sought-after aspect that has fostered research in realizing new two-dimensional materials with high surface area for rapid response and low-ppm detection of volatile organic compounds (VOCs). Herein, a fast-response and low-ppm ethanol gas sensor operating at near room temperature has been fabricated successfully by utilizing cubic mesoporous graphitic carbon nitride (g-CN, commonly known as g-C3N4), synthesized through template inversion of mesoporous silica, KIT-6. Upon exposure to 50 ppm ethanol at 250 °C, the optimized Ag/g-CN showed a significantly higher response (Ra/Rg = 49.2), fast response (11.5 s), and full recovery within 7 s in air. Results of sensing tests conducted at 40 °C show that the sensor exhibits not only a highly selective response to 50 ppm (Ra/Rg = 1.3) and 100 ppm (Ra/Rg = 3.2) of ethanol gas but also highly reversible and rapid response and recovery along with long-term stability. This outstanding response is due to its easily accessible three-dimensional mesoporous structure with higher surface area and unique planar morphology of Ag/g-CN. This study could provide new avenues for the design of next-generation room-temperature VOC sensors for effective and efficient monitoring of alarming concern over indoor environment.

Cubic mesoporous Pd–WO3 loaded graphitic carbon nitride (g-CN) nanohybrids: highly sensitive and temperature dependent VOC sensors

The urgent need for real-time monitoring of toxic/hazardous gases in the immediate indoor environment has attracted much attention owing to the recent advancements in the development of ultra-efficient gas sensors with increased accuracy and portability at around room temperature. In this work, we report on a high performance volatile organic compound (VOC) sensor using a Pd–WO3 loaded ordered mesoporous graphitic carbon nitride (g-CN)-based nanohybrid prepared via a nanocasting strategy on a hard 3D porous silica (KIT-6) template. The nanocasted Pd–WO3/g-CN sensor exhibits highly selective temperature dependent trace detection of important VOCs (formaldehyde, toluene, acetone and ethanol), which are commonly present in the indoor climate. The 3D cubic ordered mesoporous structure of the 2D layered g-CN in the hybrid nanodevice is very advantageous towards improving its sensing response with enhanced linearity, swift response/recovery time, selectivity, reversibility, stability with respect to various VOCs (at their respective optimum temperature) and reusability. The proposed functional hybrid nanomaterial-based sensing strategy offers an effective design for highly sensitive and efficient VOC detection devices, which can operate well at low temperatures also.

A porous, crystalline truxene-based covalent organic framework and its application in humidity sensing

Truxene is employed as a building block to successfully synthesize novel covalent organic frameworks (COFs). The condensation reaction between truxene (10,15-dihydro-5H-diindeno[1,2-a:1′,2′-c]fluorene, TX) and 1,4-phenylenediboronic acid (DBA) results in a crystalline COF with boron ester linkages (COF-TXDBA) and a surface area of 1526 m2 g−1, as confirmed by powder X-ray diffraction (PXRD) and Brunauer–Emmett–Teller (BET) surface area measurements. This is the first study where nanochannels generated by periodic COF planar layers are shown to ease the interactions of the boron ester linkages with the water molecules for efficient humidity sensing. The COF-TXDBA based % RH sensor exhibits a change of 3 orders of magnitude in impedance in the 11–98% RH range, with response and recovery times of 37 s and 42 s, respectively. The response transients measured by switching COF-TXDBA sensor back and forth in 4 loops of % RH range displays excellent reversibility of the sensor with a deviation of 2.3% in the switching process.

Metal–ferrite nanocomposites for targeted drug delivery

Abstract Targeted drug delivery has emerged as an astonishing medication methodology for direct treatment of the infected body organ, and it avoids the side effects caused to other healthy organs of human body. Due to the ability to carry an adequate drug concentration and release it directly to the organ to be treated, nanocomposite materials have proven to be a boon for targeted drug delivery. The present chapter aims to discuss the role of metal–ferrite nanocomposites in achieving the targeted drug delivery. This will include the elaboration of different synthesis methodologies of metal–ferrite nanocomposites along with their compositional flexibility as the synthesis route has a strong impact on the structure of nanocomposites. The performance of these nanocomposites toward drug release, as analyzed by different scientists through in vitro studies, has been discussed. The reported literature has been integrated to understand the conceptual concreteness of drug release attributes such as drug-loading efficiency, biocompatibility, drug solubility, and so on, as well as the optimization criteria. Each category of nanocomposites including nanoparticles, 1D, 2D, and 3D nanostructures has been explored with their unique attributes toward their drug carrying and drug release performance. Moreover, the chapter deals with the current advancement in drug delivery systems based on magnetic ferrite nanocomposites and possible future perspectives through a critical discussion of the loopholes that exist in present methodologies.