Engineering piezoelectricity at vdW interfaces of quasi-1D chains in 2D Tellurene.

Low-dimensional piezoelectrics have drawn attention to the realization in nano-scale devices with high integration density. A unique branch of 2D Tellurene bilayers formed of weakly interacting quasi-1D chains via van der Waals forces is found to exhibit piezoelectricity due to the semiconducting band gap and spatial inversion asymmetry. Various bilayer stackings are systematically examined using density functional theory, revealing optimal piezoelectricity when dipole arrangements are identical in each layer. Negative piezoelectricity has been observed in two of the stackings AA' and AA″ while other two stackings exhibit the usual positive piezoelectric effect. The layer-dependent 2D piezoelectricity (∣e222D ∣) increases with an increasing number of layers in contrast to the odd-even effect observed in h-BN and MoS2. Notably, the piezoelectric effect is observed in even-layered structures due to the homogeneous stacking in multilayers. Strain is found to enhance in-plane piezoelectricity by 4.5 times (-66.25 × 10-10C m-1at -5.1% strain) due to the increasing difference in Born effective charges of positively and negatively charged Te-atoms under compressive biaxial strains. Moreover, out-of-plane piezoelectricity is induced by applying an external electric field, thus implying Tellurene is a promising candidate for piezoelectric sensors.

Porous Carbon Template Decorated with MOF-Driven Bimetallic Phosphide: A Suitable Heterostructure for the Production of Uninterrupted Green Hydrogen via Renewable Energy Storage Device.

Water splitting via an uninterrupted electrochemical process through hybrid energy storage devices generating continuous hydrogen is cost-effective and green approach to address the looming energy and environmental crisis toward constant supply of hydrogen fuel in fuel cell driven automobile sector. The high surface area metal-organic framework (MOF) driven bimetallic phosphides (ZnP2 @CoP) on top of CNT-carbon cloth matrix is utilized as positive and negative electrodes in energy storage devices and overall water splitting. The as-prepared positive electrode exhibits excellent specific capacitances/capacity of 1600 F g-1 /800 C g-1 @ 1A g-1 and the corresponding hybrid device reveals an energy density of 83.03 Wh kg-1 at power density of 749.9 W kg-1 . Simultaneously, the electrocatalytic performance of heterostructure shows overpotentials of 90 mV@HER and 204 mV@OER at current density of 10 and 20 mA cm-2 , respectively in alkaline electrocatalyzer. Undoubtedly, it shows overall water splitting with low cell voltage of 1.53 V@10 mA cm-2 having faradic and solar-to-hydrogen conversion efficiency of 98.81% and 9.94%, respectively. In addition, the real phase demonstration of the overall water-splitting is performed where the electrocatalyzer is connected with a series of hybrid supercapacitor devices powered up by the 6 V standard silicon solar panel to produce uninterrupted green H2 .

Bio-piezoelectric phenylalanine-αß-dehydrophenylalanine nanotubes as potential modalities for combinatorial electrochemotherapy in glioma cells.

Bio-piezoelectric materials are endowed with characteristic features such as non-invasiveness, small energy attenuation and deep tissue penetrability. Thus, they have the ability to serve as both diagnostic and therapeutic modalities for targeting and treating various dreaded disorders scourging mankind. Herein, piezoelectric nanotubes derived from a modified amino acid-containing dipeptide, phenylalanine-αß-dehydrophenylalanine (Phe-ΔPhe; FΔF), possessing acoustic stimulation-triggered reactive oxygen species (ROS) generating ability, were employed and projected for achieving a piezo-active response enabled anti-cancer effect in glioma cells. A model anti-cancer drug doxorubicin (Dox) was also loaded into the nanotubes and the combined system depicted enhanced ROS production and cell killing under an acoustically developed piezo-catalytic environment. Cellular level assessment studies demonstrated that the dipeptide based piezoelectric nanotubes could lead to an increase in the cellular Ca2+ ion concentration, further inducing ROS-triggered cytotoxicity accompanied by high therapeutic efficacy in C6 glioma cells. Overall, our structures have the uniqueness of serving as acoustic stimulus-driven, wireless, and non-invasive electro-chemotherapeutic agents for enabling heightened cancer cell killing and may complement other chemotherapeutic modalities for treating the disease.

Super-Hydrophilic Leaflike Sn4P3 on the Porous Seamless Graphene-Carbon Nanotube Heterostructure as an Efficient Electrocatalyst for Solar-Driven Overall Water Splitting.

Water splitting using renewable energy resources is an economic and green approach that is immensely enviable for the production of high-purity hydrogen fuel to resolve the currently alarming energy and environmental crisis. One of the effective routes to produce green fuel with the help of an integrated solar system is to develop a cost-effective, robust, and bifunctional electrocatalyst by complete water splitting. Herein, we report a superhydrophilic layered leaflike Sn4P3 on a graphene-carbon nanotube matrix which shows outstanding electrochemical performance in terms of low overpotential (hydrogen evolution reaction (HER), 62 mV@10 mA/cm2, and oxygen evolution reaction (OER), 169 mV@20 mA/cm2). The outstanding stability of HER at least for 15 days at a high applied current density of 400 mA/cm2 with a minimum loss of potential (1%) in acid medium infers its potential compatibility toward the industrial sector. Theoretical calculations indicate that the decoration of Sn4P3 on carbon nanotubes modulates the electronic structure by creating a higher density of state near Fermi energy. The catalyst also reveals an admirable overall water splitting performance by generating a low cell voltage of 1.482 V@10 mA/cm2 with a stability of at least 65 h without obvious degradation of potential in 1 M KOH. It exhibited unassisted solar energy-driven water splitting when coupled with a silicon solar cell by extracting a high stable photocurrent density of 8.89 mA/cm2 at least for 90 h with 100% retention that demonstrates a high solar-to-hydrogen conversion efficiency of ∼10.82%. The catalyst unveils a footprint for pure renewable fuel production toward carbon-free future green energy innovation.

Designing an efficient bifunctional electrocatalyst heterostructure.

Oxygen and hydrogen evolutions are the two fundamental processes involved in electrocatalytic water splitting. Two dimensional (2D) transition metal dichalcogenides (TMDCs) and graphene-based materials are regarded as the emergent catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, doped graphene and molybdenum dichalcogenide heterostructures are evaluated for their catalytic activity using density functional theory (DFT). The Janus MoSSe and P-doped graphene heterostructure is found to have the best electrocatalytic activities with smaller overpotential values (ηOER = 1.67 V and ηHER = 0.10 V) as compared to those of the parent monolayers graphene (ηOER = 1.85 V and ηHER = 1.80 V) and MoS2 (ηOER = 2.99 V and ηHER = 1.72 V).

Large piezoelectric and thermal expansion coefficients with negative Poisson's ratio in strain-modulated tellurene.

Two dimensional (2D) chalcogenide monolayers have diversified applications in optoelectronics, piezotronics, sensors and energy harvesting. The group-IV tellurene monolayer is one such emerging material in the 2D family owing to its piezoelectric, thermoelectric and optoelectronic properties. In this paper, the mechanical and piezoelectric properties of 2D tellurene in centrosymmetric ß and non-centrosymmetric ß' phases are investigated using density functional theory. ß'-Te has shown a negative Poisson's ratio of -0.024 along the zigzag direction. Giant in-plane piezoelectric coefficients of -83.89 × 10-10 C m-1 and -42.58 × 10-10 C m-1 are observed for ß'-Te under biaxial and uniaxial strains, respectively. The predicted values are remarkably higher, that is 23 and 12 times the piezoelectric coefficient of a MoS2 monolayer with biaxial and uniaxial strain in the zigzag direction, respectively. A large thermal expansion coefficient of tellurene is also estimated using quasi harmonic approximation. High piezoelectricity combined with exotic mechanical and thermal properties makes tellurene a very promising candidate in nanoelectronics.