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Chemically exfoliated 1T-phase transition metal dichalcogenide nanosheets for transparent antibacterial applications
摘要： Two-dimensional transition metal dichalcogenides (TMDs) are promising materials for a range of applications owing to their intriguing properties including the excellent electrical performance and biocompatibility. Strikingly, 1T-phase TMDs have attracted significant interest based on their metallic properties with octahedral metal coordination where the phase transition can occur from the semiconducting 2H-phase to metallic 1T-phase by chemical intercalation-induced exfoliation process. In this regard, 1T-phase TMDs have great potential in antibacterial agents in terms of effective charge transfer between the bacterial membrane and TMD nanosheets while their biological interactions have been underexplored. To bridge this gap, we herein investigate the antibacterial activities of various 1T-phase TMDs including molybdenum disulfide (MoS2), tungsten disulfide (WS2), and molybdenum diselenide (MoSe2) toward Gram-negative bacteria Escherichia coli that exhibit the reduction of bacterial viability caused by the production of reactive oxygen species, oxidation of glutathione and other chemical functionalities. The effective antibacterial capacity of metallic 1T-phase TMDs is observed and their bactericidal mechanisms are investigated in terms of their electrical conductivity and chemical oxidation property that induce the charge transfer from bacterial membrane to TMDs leading to the continuous disruption of bacteria and loss of cellular components. Furthermore, we demonstrated the transparent antibacterial films consisting of 1T-phase TMDs in which TMD nanosheets are immobilized on the surfaces and their basal planes play an important role in antibacterial actions for practical biomedical applications. Thus, our findings provide new insights into the great potential of 1T-phase TMDs as promising building blocks for antibacterial surfaces and contribute to the widespread use of 1T-phase TMDs for practical biomedical applications.
关键词： 1T-phase,charge transfer,antibacterial activity,oxidative stress,transition metal dichalcogenide
更新于2025-11-21 11:08:12
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Antimicrobial-Peptide-Conjugated MoS2 Based Nanoplatform for Multimodal Synergistic Inactivation of Superbugs
摘要： Development of new antibacterial therapeutics material is becoming increasingly urgent due to the huge threat of superbugs, which are responsible for more than half million death each year in this world. Here, we report the development of novel nano-biomaterial based on melittin antimicrobial peptide (AMP) attached transition metal dichalcogenide MoS2 based theranostic nanoplatform. Reported nanoplatform has capability for targeted identification and synergistic inactivation of 100% multidrug-resistant superbugs by combined photo thermal therapy (PTT), photodynamic therapy (PDT) and AMP process. A novel approach for the design of melittin antimicrobial peptide attached MoS2 based nanoplatform is reported, which emits very bright and photo stable fluorescence. It also generates heat as well as reactive oxygen species (ROS) in the presence of 670 nm near infrared light, which allow it to be used as PTT & PDT agent. Due to the presence of AMP, multifunctional AMP exhibits significantly improved antibacterial activity for superbugs via multimodal synergistic killing mechanism. Reported data demonstrate that nanoplatforms are capable of identification of multidrug-resistant superbugs via luminescence imaging. Experimental results show that it is possible to kill only ~45% of superbugs via MoS2 nanopaltform based on PTT & PDT processes together. On the other hand, killing of less than 10% of superbugs is possible using melittin antimicrobial peptide alone. Whereas, 100% Methicillin-resistant Staphylococcus aureus (MRSA), drug resistance Escherichia coli (E. coli) and drug resistance Klebsiella pneumoniae (KPN) superbugs can be killed using antimicrobial peptide attached MoS2 QDs, via synergistic killing mechanism. Mechanisms for possible synergistic killing of multidrug-resistant superbugs have been discussed.
关键词： theranostic transition metal dichalcogenide,photodynamic therapy,multimodal therapy for multidrug-resistant superbugs,Melittin antimicrobial peptide attached MoS2 based nanoplatform,photo thermal therapy
更新于2025-09-23 15:23:52
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Understanding Spatiotemporal Photocarrier Dynamics in Monolayer and Bulk MoTe <sub/>2</sub> for Optimized Optoelectronic Devices
摘要： Semiconducting molybdenum ditelluride has emerged as a promising transition-metal dichalcogenide with a number of novel properties. In particular, its bandgap in infrared range makes it an attractive candidate for ultrathin and high-performance infrared optoelectronic applications. Dynamical properties of photocarriers play a key role in determining performance of such devices. We report an experimental study on spatiotemporal dynamics of photocarriers in both monolayer and bulk MoTe2. Transient absorption measurement in reflection geometry revealed ultrafast thermalization and relaxation processes of photocarriers and lifetimes of about 60 and 80 ps in monolayer and bulk MoTe2, respectively. By spatially resolved transient absorption measurements on monolayer, we obtained an exciton diffusion coefficient of 20 ± 10 cm2 s?1, a mean free time of 200 fs, a mean free path of 20 nm, and a diffusion length of 350 nm. The corresponding values for the bulk sample are 40 ± 10 cm2 s?1, 400 fs, 40 nm, and 570 nm, respectively. These results provide fundamental information for understanding and optimizing performance of MoTe2-based optoelectronic devices.
关键词： two-dimensional material,exciton,transient absorption,molybdenum ditelluride,transition-metal dichalcogenide,diffusion,photocarrier dynamics
更新于2025-09-23 15:23:52
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High-Performance p-BP/n-PdSe2 Near-Infrared Photodiode with Fast and Gate-Tunable Photoresponse
摘要： Van der Waals heterostructures composed of transition metal dichalcogenide (TMDs) materials have become a remarkable compact system that could offer an innovative architecture for advanced engineering in high-performance energy-harvesting and optoelectronic devices. Here, we report a novel van der Waals (vdW) TMDs heterojunction photo-diode composed of black phosphorus (p-BP) and palladium diselenide (n-PdSe2) which establish a high and tunable rectification and photoresponsivity. A high rectification up to ≈ 7.1 × 105 is achieved which is successfully tuned by employing the back gate voltage to the heterostructure devices. Besides, the device significantly shows the high and gate-controlled photoresponsivity of ?? = 9.6 × 105 ?? ?? ―1, 4.53 × 105 ???? ―1 and 1.63 × 105 ???? ―1 under the influence of light of different wavelengths (?? = 532, 1064 and 1310 nm) in visible and near-infrared regions respectively due to interlayer optical transition and low Schottky. The device also demonstrates extraordinary values of detectivity (?? = 5.8 × 1013 Jones) and external quantum efficiency (?????? ≈ 9.4 × 106), which are an order of magnitude higher than the currently reported values. The effective enhancement of photovoltaic characteristics in visible and infrared regions of this TMDs heterostructure based system has a huge potential in the field of optoelectronics to realize high-performance infrared photodetectors.
关键词： rectification,palladium diselenide,detectivity,photoresponsivity,transition metal dichalcogenide materials,near-infrared
更新于2025-09-23 15:21:01
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Ultrafast dynamics in van der Waals heterostructures
摘要： Van der Waals heterostructures are synthetic quantum materials composed of stacks of atomically thin two-dimensional (2D) layers. Because the electrons in the atomically thin 2D layers are exposed to layer-to-layer coupling, the properties of van der Waals heterostructures are defined not only by the constituent monolayers, but also by the interactions between the layers. Many fascinating electrical, optical and magnetic properties have recently been reported in different types of van der Waals heterostructures. In this Review, we focus on unique excited-state dynamics in transition metal dichalcogenide (TMDC) heterostructures. TMDC monolayers are the most widely studied 2D semiconductors, featuring prominent exciton states and accessibility to the valley degree of freedom. Many TMDC heterostructures are characterized by a staggered band alignment. This band alignment has profound effects on the evolution of the excited states in heterostructures, including ultrafast charge transfer between the layers, the formation of interlayer excitons, and the existence of long-lived spin and valley polarization in resident carriers. Here we review recent experimental and theoretical efforts to elucidate electron dynamics in TMDC heterostructures, extending from timescales of femtoseconds to microseconds, and comment on the relevance of these effects for potential applications in optoelectronic, valleytronic and spintronic devices.
关键词： spin and valley polarization,charge transfer,valleytronic,transition metal dichalcogenide,Van der Waals heterostructures,excited-state dynamics,spintronic devices,interlayer excitons,optoelectronic
更新于2025-09-23 15:21:01
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Giant Stark effect in coupled quantum wells: Analytical model
摘要： Coupled quantum wells have been proposed as candidates for highly polarizable structures due to their near-degenerate and dipole-coupled electronic states. Hence, many interesting applications in linear and nonlinear optics can be envisioned. We analyze this proposal considering a simple structure with a delta-function barrier separating the wells. While very substantial Stark shifts are certainly predicted for this geometry, perturbative estimates based on polarizabilities (and hyperpolarizabilities) fail beyond a critical ?eld strength that depends inversely on the barrier. Hence, a giant Stark effect due to near-degenerate states is invariably limited by a small critical ?eld. Our analytical (hyper) polarizability expressions are applied to ?nd quantitative Stark shifts for GaAs quantum wells and transition-metal dichalcogenide bilayers. The predicted Stark shifts and critical ?elds agree with the ?eld dependence observed in a range of available experiments.
关键词： Stark effect,hyperpolarizability,GaAs,transition-metal dichalcogenide bilayers,polarizability,coupled quantum wells
更新于2025-09-23 15:19:57
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Controlled polymer crystal/two-dimensional material heterostructures for high-performance photoelectronic applications
摘要： Controlled polymer crystal/two-dimensional material heterostructures for high-performance photoelectronic applications
关键词： epitaxy,epitaxial interaction,semiconducting polymer,graphene,crystal interaction,transition-metal dichalcogenide,ferroelectric polymer,two-dimensional materials
更新于2025-09-19 17:13:59
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Ambient atmosphere laser-induced local ripening of MoS <sub/>2</sub> nanoparticles
摘要： Transition metal dichalcogenide (TMDC) ultrathin layers have attracted considerable interest in the recent years. Their peculiar functional properties can be exploited in electronics, spintronics, optoelectronics, photonics, energy production, harvesting and storage. The availability of cost-effective, green, and efficient growth processes is of paramount importance and significant effort has been made in the research on various production methodologies. Here we report on a simple laser-based process which allows the direct writing of thin TMDC layers. In detail, by direct exposure to laser irradiation of a dip-coated MoS2 precursor, we obtained a three-dimensional arrangement of MoS2 nanoparticles in the form of platelets with a lateral dimension of about 50 nm and thickness down to bilayers. The characterization was assessed by AFM and Raman spectroscopy. The platelets are formed only in the central region of the laser spot, confirming that the material out of the spot is indeed an unprocessed precursor. By tuning the precursor deposition, we demonstrate the fabrication of MoS2 patterns with designed layer numbers. The proposed approach is highly versatile and can be applied also for the controlled growth of other TMDCs, as proved by the successful generation of WS2 layers.
关键词： Transition metal dichalcogenide,MoS2,direct writing,laser-induced,Raman spectroscopy,AFM
更新于2025-09-16 10:30:52
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[IEEE TENCON 2019 - 2019 IEEE Region 10 Conference (TENCON) - Kochi, India (2019.10.17-2019.10.20)] TENCON 2019 - 2019 IEEE Region 10 Conference (TENCON) - An Alternative Approach to Voltage Dependent Reduction of Schottky Barrier Height Modeling in Two Dimensional MSM Photodetectors
摘要： Current-voltage (I-V) characteristics of a two dimensional MSM photodetector can be explained by modified thermionic emission diffusion (TED) theory. The theory assumes that Schottky barrier height (SBH) decreases linearly with bias voltage and hence voltage dependent reduction of SBH is understood in term of a series resistance (Rs) and ideality factor (n). Characterization of Rs and n can be done from dV d(lnI) vs I plot. However, in this paper we are presenting an alternative approach to understanding characteristics of voltage dependent reduction of SBH. We are proposing an exponential relationship between reduction of SBH and bias voltage to understand non ideality of Schottky junctions. By applying this relationship directly into the Richardson-Dushman equation photocurrents of different Transition-Metal Dichalcogenides(TMD) based devices can be estimated analytically. This model offers a simplistic approach for understanding non ideal behaviour of Schottky barrier height. Using this model we have calculated I-V characteristics of four different TMD based photodetectors under illumination as reported in literature. We have observed good agreement of our calculated results with experimental values. Mean absolute error in each of the cases was found to be not more than 6% in these calculations.
关键词： Perovskite,Voltage Dependent Schottky Barrier Height,Transition-Metal Dichalcogenide,Photodetector
更新于2025-09-16 10:30:52
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Nonlinear optics at excited states of exciton polaritons in two-dimensional atomic crystals
摘要： Exciton polaritons (EP) are partial-light partial-matter quasiparticles in semiconductors demonstrating striking quantum phenomena such as Bose-Einstein condensation and single-photon nonlinearity. In these phenomena, the governing process is the EP relaxation into the ground states upon excitation, where various mechanisms are extensively investigated with thermodynamic limits. However, the relaxation process becomes drastically different and could significantly advance the understanding of EP dynamics for these quantum phenomena, when excited states of EP are involved. Here, for the first time, we observe nonlinear optical responses at the EP excited states in a monolayer tungsten disulphide (WS2) microcavity, including dark excited states and dynamically metastable upper polariton band. The nonlinear optics leads to unique emissions of ground states with prominent valley degree of freedom (DOF) via anomalous relaxation process, which is applicable to a wide range of semiconductors from monolayer transition metal dichalcogenides (TMDs) to emerging halide perovskites. This work promises possible approaches to challenging experiments such as valley polariton condensation. Moreover, it also constructs a valley-dependent solid state three-level system for terahertz photonics and stimulated Raman adiabatic passage.
关键词： excited states,exciton-polaritons,relaxation dynamics,Nonlinear optics,monolayer transition metal dichalcogenide
更新于2025-09-16 10:30:52