TeNWs/Ti₃C₂T<i>_x</i> Nanohybrid-Based Flexible Pressure Sensors for Personal Safety Applications Using Morse Code

This report demonstrates the fabrication and development of a tellurium nanowire (TeNW) and MXene (Ti3C2Tx) nanohybrid-based pressure sensor. The fabricated sensor was later encapsulated in poly(dimethylsiloxane) (PDMS) and used as buttons for the communication system to demonstrate a personal safety application using Morse code. The fabricated pressure sensor demonstrated an excellent sensitivity of 9.29241 kPa–1 and stability withstanding over ∼3000 cycles of applied pressure (∼1.729 kPa). Real-time ultraviolet photoelectron spectroscopy (UPS) is utilized for realizing the band diagram of the TeNWs/Ti3C2Tx nanohybrid to understand the transport of charge carriers upon external pressure. The transduction mechanism of the fabricated pressure sensor is explained using the improved intrinsic piezoresistive properties of the MXene and TeNWs in TeNWs/Ti3C2Tx, which helps in increasing the tunneling current by a decrease in the effective interlayer resistance/interwire tunneling distance of the nanohybrid. Further, an Android application was created to wirelessly receive data via Bluetooth from the sensors connected to a microcontroller. The application displayed the pattern pressed on the sensors as a Morse dash or dot. This can further be used in a similar fashion to that of a telegraph to send complex messages such as “HELP”. Developing a TeNWS/Ti3C2Tx nanohybrid-based flexible sensor opens many possible wireless monitoring and communication applications

Fig 3 -

a) Graph showing different currents at different temperatures b) Graph showing decrease in barrier height with increase in temperature. c) Graph showing increase in reverse saturation current with increase in temperature. d)graph showing NSS at different temperatures. e) Responsivity at different temperatures.</p

S2 Fig -

a) The Raman and b) PL spectra of monolayer MoS2 that has been nitrogen-doped and undoped on a SiO2/Si substrate. (TIF)</p

S3 Fig -

a-b-c) UPS spectra (measured by He I source, hν = 21.22 eV) of n-type silicon substrate, undoped MoS2 and nitrogen doped MoS2 grown on n-type substrate. c)Schematic representation of energy-band diagram n-type of silicon substrate and undoped MoS2 in equilibrium condition (when isolated) d) energy-band diagram n-type of silicon substrate and nitrogen doped MoS2 in equilibrium condition (when isolated). (TIF)</p

Fig 1 -

a) Graph showing I-V for undoped MoS2/n-Si device. b) Graph showing I-V for nitrogen doped MoS2/n-Si device. c) Nss of both nitrogen doped MoS2/n-Si junction and undoped MoS2/n-Si junction. d-e) Graph showing I-V’s for both undoped and doped MoS2/n-Si device. f-g) Graph showing temporal response for constant light intensity for both nitrogen doped and undoped MoS2/n-Si device. h-i) Graph showing temporal response for variable light intensity for both nitrogen doped and undoped MoS2/n-Si device. j) responsivity of nitrogen doped and undoped MoS2/n-Si junction. k-l) rise time for both undoped and doped MoS2/n-Si device.</p

Comparison of responsivities values with existing literature.

Comparison of responsivities values with existing literature.</p

Flexible, Disposable Cellulose-Paper-Based MoS₂/Cu₂S Hybrid for Wireless Environmental Monitoring and Multifunctional Sensing of Chemical Stimuli

Multifunctional sensors responding to different chemical stimuli fabricated using functional nanomaterials still remain a challenge because of the usage of the same sensor multiple times for different sensing applications and unreliable front-end processing of the sensing data. This challenge is intensified by the lack of suitable techniques for fabricating disposable sensors, which can be integrated into smartphones with a dedicated application developed for each sensing application. A novel MoS₂/Cu₂S hybrid grown on disposable cellulose paper by the hydrothermal method is reported for its utilization in sensing humidity, temperature, breath, and ethanol adulteration, wherein the data can be wirelessly transmitted to a smartphone with the dedicated application module for each sensing application. The sensor can be utilized for a particular sensing application and then can be disposed, avoiding the need for utilizing the same sensor for different sensing applications, thereby increasing the accuracy of the sensing data. The sensing mechanism of the fabricated sensor is explained for each stimulus in terms of change in the transport properties of the MoS₂/Cu₂S hybrid. The development of such unique hybrid materials for wireless disposable multifunctional sensors is a great step ahead in flexible and wearable electronics having potential applications in medical, security, Internet of things, etc

Fig 2 -

a-b) Schematic representing band diagram of n-type Si substrate and n-type undoped MoS2 both when isolated and when contacted. c-d) Band diagram of n-type Si substrate and n-type nitrogen doped MoS2 both when isolated and contacted.</p

S1 Fig -

a) FESEM images of nitrogen doped MoS2. b) HRTEM image of monolayer MoS2 c) XPS survey spectra of N-doped MoS2, d), e) & f) Individual high-resolution XPS spectra of Mo 3d, S 2p & N 1s of nitrogen doped MoS2. (TIF)</p

Mixed-Dimensional van der Waals Heterostructure (2D ReS₂/0D MoS₂ Quantum Dots)-Based Broad Spectral Range with Ultrahigh-Responsive Photodetector

The remarkable properties of two-dimensional (2D) materials have led to significant advancements in photodetection and optoelectronics research. Currently, there are many successful methods that are employed to improve the responsivity of photodetectors, but the limited spectral range of the device remains a limitation. This work demonstrates the development of a mixed-dimensional (2D/0D) hybrid photodetector device fabricated using chemical vapor deposition (CVD)-grown monolayer ReS2 and solution-processed MoS2 quantum dots (QDs). The mixed dimensionality of 2D (ReS2) and zero-dimensional (0D) MoS2 QDs assist in improving the spectral range of the device [ultraviolet (360 nm) to near-infrared (780 nm)]. Further, due to the work function difference between ReS2 and MoS2 QDs, the built-in electric field across the mixed-dimensional interface promotes effective charge separation and migration, resulting in improved responsivities of the device. The calculated responsivities of the fabricated photodetector are 5.4 × 102, 3.3 × 102, and 2.6 × 102 A/W when subjected to visible, UV, and NIR light illumination, which is remarkable when compared to the existing reports on broadband photodetection. The mixed-dimensionality heterostructure coupled with contact engineering paves the way for highly responsive broadband photodetectors for potential applications in security, healthcare, etc