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Monolayer MoS2 flakes are prepared by low‐pressure chemical vapor deposition on p‐type and n‐type silicon substrates and post‐treated under nitrogen (N2)‐rich conditions to incorporate nitrogen atoms in sulfur vacancies. Ultraviolet photoelectron spectroscopy (UPS) shows an increase in work function value by 0.47 eV and 0.53 eV compared to undoped MoS2 when grown on p and n‐type substrates, respectively. Photodetection experiments conducted for doped and undoped MoS2 grown on p‐type substrate reveal a decrease in the value of photo responsivity for N2 doped MoS2 (191 A W−1) compared with undoped MoS2 (572 A W−1). Also, MoS2 crystals grown and doped on an n‐type substrate display an important enhancement of the photoresponsivity from 63 A W−1 for undoped to 606 A W−1 for N2 doped MoS2. The modulation of Schottky barrier height for N2 doped MoS2 on p type substrate decreased whereas for n type substrate the high electric field created due to the difference in the Fermi level allows for greater separation of photogenerated charge carriers. This modulation in the photoresponsivity due to the selection of the type of substrate opens up new avenues of research and engineering of atomically thin optoelectronic devices. [ABSTRACT FROM AUTHOR]

Even though there are various reports on the fabrication of flexible photodetectors, still there is a need for the development of high-performance photodetectors. In recent years, the plasmonic photodetection technique has emerged as one of the prominent solutions to enhance photodetection performance. In this work, a flexible and high-performance broadband (visible-near-infrared (NIR)) plasmonic photodetector is demonstrated by integrating gold (Au) nanoparticles (NPs) on two-dimensional (2D) ReS2 nanosheets. Fabricated Au-NPs/ReS2 showed an approximately 15-fold enhancement in the photodetection performance compared to pristine ReS2. Photoresponsivity of the fabricated Au-NPs/ReS2 device in visible (Vis) and NIR regions is ∼2.1 and ∼1.3 A W–1, respectively. Significant enhancement in the photosensing performance of the device could be a combined effect of multiple factors, including localized surface plasmon resonance and effective charge transfer at the interface of Au-NPs and ReS2. The response speed of the fabricated device is approximately 200 ms. Furthermore, theoretical understanding of light interaction with Au-NPs is studied, and also electromagnetic simulations are performed using Lumerical Finite Difference Time Domain Multiphysics simulation to investigate the plasmon coupling effect of Au-NPs on 2D ReS2 nanosheets. To further understand the photodetection mechanism, the energy band diagram of the Au-NPs/ReS2 interface is drawn using ultraviolet photoelectron spectroscopy measurements. [ABSTRACT FROM AUTHOR]

Over the last decade, the rapid development in health care industry and security has driven innovations in the field of wearable electronics and smart sensors. This report demonstrates the fabrication of molybdenum diselenide (MoSe2) by a facile, low-cost and scalable hydrothermal synthesis method followed by a vacuum filter deposition on cellulose paper. The fabricated device is utilized as a pressure and strain sensor. The fabricated device is passivated using polydimethylsiloxane (PDMS), and also, PDMS film enhances the flexibility of the device. The calculated sensitivity of pressure sensor is ~0.3 kPa−1, which is comparable and relatively better than the pressure sensor fabricated using sophisticated techniques. Furthermore, the device exhibited significant of merit for strain sensing with a gauge factor of ~6.84. The fabricated device showed excellent resilience in 500 cycle bending tests, which promises the robustness of the device. As an application, the fabricated sensor is used to develop a wireless keyboard by integrating the sensor on fingertips of an individual and a real-time human motion monitoring application in which the data are transmitted wirelessly to a smartphone with a dedicated android application. The successful fabrication of MoSe2/paper-based cost-effective, flexible, and biodegradable pressure-strain sensor shows tremendous applications in future intelligent user interface systems, human security, and personal health care monitoring. [ABSTRACT FROM AUTHOR]

The effective incorporation of novel and highly conductive hybrid functional nanomaterials onto flexible and porous substrates is extremely desirable to develop flexible supercapacitors. Herein, a novel 2D/0D-MoS2/SnS2 on a flexible cellulose paper substrate has been demonstrated for its utilization in flexible supercapacitors. The surface morphology and particle size of the MoS2 and SnS2 QDs, elemental composition, absorption spectra, and crystallinity have been analyzed thoroughly. Further, to explore the supercapacitor applications, the electrochemical response has been studied. The obtained results demonstrate that both the pristine MoS2 and MoS2/SnS2 QDs composites on cellulose paper exhibited excellent electrochemical performance. The specific capacitance for the pristine MoS2 and MoS2/SnS2 QDs displayed 422.2 F g−1 and 277.1 F g−1 at 0.5 A g−1 current density using a conventional two-electrode system. The drop-casting of SnS2 QDs provides better electrochemical active sites, which contributed to the enhanced specific capacitance of the composite structure. Moreover, it is shown that cellulose paper as an electrode material, using MoS2 and MoS2/SnS2 QDs, is applied as a supercapacitor for potential utilization in wearable electronics applications. [ABSTRACT FROM AUTHOR]

Even though there are reports on flexible photodetectors, one of the main issues that still needs to be resolved is the lower values of responsivity arising due to the use of non‐conventional substrates such as polymers, cellulose paper, etc. There are ways to improve the responsivity, such as piezotronics and surface plasmonic resonance, but studies on utilizing the same for flexible substrates remain limited. Further, the comparative performance of different nanoparticles (NPs) remains unexplored. This report demonstrates the fabrication of flexible visible/near‐infrared (NIR) photodetectors by functionalizing MoS2 grown on paper substrate with various noble metal NPs such as gold (Au), platinum (Pt), and palladium (Pd) for enhanced photoresponse. The metal NPs‐MoS2 (Au, Pt, and Pd‐NPs‐MoS2) based photodetector shows a prominent improvement in the photoresponse characteristics when compared to pristine MoS2. Enhancement in the photodetector performance is mainly due to the localized surface plasmon resonance of prepared metal NPs and the increase in incident light scattering. Out of the fabricated metal NPs‐MoS2 photodetectors, Au‐NPs/MoS2 shows maximum responsivity of 99.3 and 46.03 mA W−1 under visible and NIR region, respectively which is ≈80 times higher than pristine MoS2. [ABSTRACT FROM AUTHOR]

In the current study, noble metal nanoparticle functionalized MoS2 coated biodegradable low-cost paper sensors were fabricated for the selective detection of low concentrations of volatile organic compounds (VOCs). A MoS2 layer was grown on flexible cellulose paper by a two-step hydrothermal route and functionalized further by using noble metal nanoparticles like Au, Pd and Pt by a spray coating technique. MoS2 nanoflakes aggregating into a micro-flower morphology was confirmed by field emission scanning electron microscopy. X-ray photoelectron spectroscopy authenticated the existence of noble metal nanoparticles on the MoS2 surface. Sensors were then tested with seven different VOCs (≤100 ppm) of ketones, alcohols and aromatic hydrocarbon groups. Au–MoS2 and Pd–MoS2 showed inherent acetone and benzene selectivity with 50.5% and 45.7% responses, respectively, after exposure to 100 ppm concentrations at 50 °C. Paper sensors exhibited highly stable baseline resistances, less sensitivity towards humidity (∼75% RH) and an acceptable response/recovery time within 3–6 min at low temperature (50 °C). An additional effort was devoted to discriminating and recognizing different VOCs by using suitable classification algorithms utilizing four types of paper sensors, i.e. pure, Au, Pd and Pt MoS2. Principal component analysis and logistic regression schemes successfully classified five VOCs among the seven. Moreover, the sensing mechanism of the noble metal modified MoS2 paper sensor is discussed in light of the Schottky barrier model. [ABSTRACT FROM AUTHOR]

This report demonstrates the fabrication of all MoS2 based 2D/0D unipolar heterojunctions using a simple one pot hydrothermal process and their utilization in a flexible broadband photodetector covering the spectral range from the ultraviolet to the near infrared region. The discontinuous deposition of 0D MoS2, which has absorbance in the UV region, on 2D MoS2, having absorbance in the visible and near-infrared (NIR) regions, enables broadband detection. Further, contact engineering was performed wherein both the metal contacts were fabricated on 2D MoS2, thereby enabling the effective capture of photogenerated carriers. Also, a unipolar junction formed due to the Fermi level difference between 2D and 0D MoS2 produces a localized electric field that helps in the efficacious separation of photogenerated electron–hole pairs. The responsivity values of the fabricated photodetector were calculated to be 7.56 mA W−1, 12.8 mA W−1, and 3.95 mA W−1 in the UV, visible and NIR regions, respectively, indicating that the fabricated device is more sensitive towards the visible region. A detailed understanding of the photodetection mechanism of this unique heterostructure is presented using bandgap theory and trap states. The successful demonstration of such a cost-effective, scalable 2D/0D based broadband photodetector should lead to potential applications in optoelectronics, security, and wearable electronics. [ABSTRACT FROM AUTHOR]

This report demonstrates the fabrication of a flexible, water-soluble MoS2 QDs/PVA (polyvinyl alcohol) film sandwiched between Cu electrodes as a resistive memory. The active material film (MoS2 QD/PVA) of the device exhibited outstanding water solubility, dissolving the active material completely in ∼180 s, making it a promising candidate for transient/destructible memories. The device exhibited significant merits with an ON/OFF ratio of ∼150 with good cycling stability, excellent reproducibility, and data retention capability up to 1000 cycles. The memristive phenomena can be accounted for by the charge trapping, de-trapping, and quantum tunneling effects observed in nanoscale MoS2 QDs. The successful fabrication of the water-soluble MoS2 QDs/PVA resistive RAM opens up new avenues and opportunities for the development of transient memory in the fields of military, security devices, and intelligence applications. [ABSTRACT FROM AUTHOR]

Atomically thin two-dimensional (2D) materials have gained significant attention from the research community in the fabrication of high-performance optoelectronic devices. Even though there are various techniques to improve the responsivity of the photodetector, the key factor limiting the performance of the photodetectors is constrained photodetection spectral range in the electromagnetic spectrum. In this work, a mixed-dimensional 0D/2D SnS 2 -QDs/monolayer MoS 2 hybrid is fabricated for high-performance and broadband (UV-visible-near-infrared (NIR)) photodetector. Monolayer MoS 2 is deposited on SiO 2 /Si using chemical vapor deposition (CVD), and SnS 2 -QDs are prepared using a low-cost solution-processing method. The high performance of the fabricated 0D/2D photodetector is ascribed to the band bending and built-in potential created at the junction of SnS 2 -QDs and MoS 2 , which enhances the injection and separation efficiency of the photoexcited charge carriers. The mixed-dimensional structure also suppresses the dark current of the photodetector. The decorated SnS 2 -QDs on monolayer MoS 2 not only improve the performance of the device but also extends the spectral range to the UV region. Photoresponsivity of the device for UV, visible, and NIR region is found to be ∼278, ∼ 435, and ∼189 A/W, respectively. Fabricated devices showed maximum responsivity under the visible region attributed to the high absorbance of monolayer MoS 2 . The response time of the fabricated device is measured as ∼100 ms. These results reveal that the development of a mixed-dimensional (0D/2D) SnS 2 -QDs/MoS 2 -based high-performance and broadband photodetector is technologically promising for next-generation optoelectronic applications.