Unlocking the Potential: Atomically Thin 2D Fluoritene from Exfoliated Fluorite Ore and Its Electrochemical Activity.

Fluorite mineral holds significant importance because of its optoelectronic properties and wide range of applications. Here, we report the successful exfoliation of bulk fluorite ore (calcium fluoride, CaF2) crystals into atomically thin two-dimensional fluoritene (2D CaF2) using a highly scalable liquid-phase exfoliation method. The microscopic and spectroscopy characterizations show the formation of (111) plane-oriented 2D CaF2 sheets with exfoliation-induced material strain due to bond breaking, leading to the changes in lattice parameter. Its potential role in electrocatalysis is further explored for deeper insight, and a probable mechanism is also discussed. The 2D CaF2 with long-term stability shows overpotential values of 670 and 770 mV vs RHE for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, at 10 mA cm-2. Computational simulations demonstrate the unique "direct-indirect" band gap switching with odd and even numbers of layers. Current work offers new avenues for exploring the structural and electrochemical properties of 2D CaF2 and its potential applicability.

Gd3+ Encapsulation on 2D-g-C3N4 Nanostructure for Spintronics and Ultrasound Assisted Photocatalytic Applications: First-Principles and Experimental Studies.

Atomically thin two-dimensional (2D) semiconductors have high potential in optoelectronics and magneto-optics appliances due to their tunable band structures and physicochemical stability. The work demonstrates that Gd3+ incorporated 2D-g-C3N4 nanosheet (Gd3+/2D-g-C3N4 NS) is synthesized through chemisorption methodology for defect enrichment. The material characterizations reveal that the ion decoration enhances the surface area and defect concentration of the 2D sheet. The experimental observations have been further corroborated with the help of density functional theory (DFT) simulation. Spin asymmetry polarizations near the Fermi level, obtained through the partial density of states (PDOS) analyses, reveal the magnetic nature of the synthesized material, validating the room temperature ferromagnetism obtained through a vibrating-sample magnetometer (VSM). Gd3+/2D-g-C3N4 NS shows significant enhancement in saturation magnetization (Ms) experimentally and computationally compared to the pristine one. The magnetic catalyst shows 98% remediation efficiency for ultrasound-assisted visible-light-driven photodegradation of methyl orange (MO). The synergistic approach of liquid chromatography-mass spectrometry (LC-MS) analyses and DFT studies elucidates reaction intermediates and unveils the degradation mechanism. Post-characterization studies assure the stability of the magnetic catalyst through optical, chemical, magnetic, and microscopic analyses. So, the synthesized material can be proficiently used as a magnetic nanocatalyst in wastewater treatments and spin-electronics applications.

High-entropy-based nano-materials for sustainable environmental applications.

High entropy materials (HEMs), epitomized by high entropy alloys (HEAs), have sparked immense interest for a range of clean energy and environmental applications due to their remarkable structural versatility and adjustable characteristics. In the face of environmental challenges, HEMs have emerged as valuable tools for addressing issues ranging from wastewater remediation to energy conversion and storage. This review provides a comprehensive exploration of HEMs, spotlighting their catalytic capabilities in diverse redox reactions, such as carbon dioxide reduction to value-added products, degradation of organic pollutants, oxygen reduction, hydrogen evolution, and ammonia decomposition using electrocatalytic and photocatalytic pathways. Additionally, the review highlights HEMs as novel electrode nanomaterials, with the potential to enhance the performance of batteries and supercapacitors. Their unique features, including high capacitance, electrical conductivity, and thermal stability, make them valuable components for meeting crucial energy demands. Furthermore, the review examines challenges and opportunities in advancing HEMs, emphasizing the importance of understanding the underlying mechanisms governing their catalytic and electrochemical behaviors. Essential considerations for optimizing the HEM performance in catalysis and energy storage are outlined to guide future research. Moreover, to provide a comprehensive understanding of the current research landscape, a meticulous bibliometric analysis is presented, offering insights into the trends, focal points, and emerging directions within the realm of HEMs, particularly in addressing environmental concerns.

Quasicrystal Nanosheet/α-Fe2O3 Heterostructure-Based Low Power NO2 Sensors: Experimental and DFT Studies.

Industrial emissions, environmental monitoring, and medical fields have put forward huge demands for high-performance and low power consumption sensors. Two-dimensional quasicrystal (2D QC) nanosheets of metallic multicomponent Al70Co10Fe5Ni10Cu5 have emerged as a promising material for gas sensors due to their excellent catalytic and electronic properties. Herein, we demonstrate highly sensitive and selective NO2 sensors developed by low-cost and scalable fabrication techniques using 2D QC nanosheets and α-Fe2O3 nanoparticles. The sensitivity (ΔR/R%) of the optimal amount of 2D QC nanosheet-loaded α-Fe2O3 sensor was 32%, which is significantly larger about 3.5 times than bare α-Fe2O3 sensors for 1 ppm of NO2 at 150 °C operating temperature. The sensors exhibited p-type conduction, and resistance was reduced when exposed to NO2, an oxidizing gas. The enhanced sensing characteristics are a result of the formation of nanoheterojunctions between 2D QC and α-Fe2O3, which improved the charge transport and provided a large sensing signal. In addition, the heterojunction sensor demonstrated excellent NO2 selectivity over other oxidizing and reducing gases. Furthermore, density functional theory calculation examines the adsorption energy and charge transfer between NO2 molecules on the α-Fe2O3(110) and QC/α-Fe2O3(110) heterostructure surfaces, which coincides well with the experimental results.

Biotene: Earth-Abundant 2D Material as Sustainable Anode for Li/Na-Ion Battery.

Natural ores are abundant, cost-effective, and environmentally friendly. Ultrathin (2D) layers of a naturally abundant van der Waals mineral, Biotite, have been prepared in bulk via exfoliation. We report here that this 2D Biotene material has shown extraordinary Li-Na-ion battery anode properties with ultralong cycling stability. Biotene shows 302 and 141 mAh g-1 first cycle-specific charge capacity for Li- and Na-ion battery applications with ∼90% initial Coulombic efficiency. The electrode exhibits significantly extended cycling stability with ∼75% capacity retention after 4000 cycles even at higher current densities (500-2000 mA g-1). Further, density functional theory studies show the possible Li intercalation mechanism between the 2D Biotene layers. Our work brings new directions toward designing the next generation of metal-ion battery anodes.

Enhanced toughness and strength of 3D printed carbide-oxide composite for biomedical applications.

Natural materials derived/extracted Ceramics is an excellent material for developing ceramic-based orthopedic implants. Recently, we have demonstrated an easily scalable, energy-efficient green method to extract ceramic particles from bio-waste i.e. chicken bone. Though the chicken bone extract (CBE) has good biocompatibility, it lacks good mechanical properties in the 3D printed condition as that of human bones. Here, we have reinforced CBE with different weight proportions of silicon carbide to improve the mechanical characteristics of the composite. The hybrid of CBE (oxide) and carbide (SiC) is sintered at different temperatures to understand the effect of the interface of the two ceramics. It is observed that temperature has minimal effect and composition has a noticeable effect on mechanical strength as well as bio-toxicity. The toughness (∼3.58 MJ/m3) and compressive strength (∼64.64 MPa) of the 90:10 composition sintered at 1250 °C show the maximum optimum values. A mathematical model has also been developed to predict and correlate the toughness with porosity, volumetric loading, and elastic modulus of the 3D-printed ceramic composite.

Flexible Nanogenerators Based on Enhanced Flexoelectricity in Mn3O4 Membranes.

Atomically thin, few-layered membranes of oxides show unique physical and chemical properties compared to their bulk forms. Manganese oxide (Mn3O4) membranes are exfoliated from the naturally occurring mineral Hausmannite and used to make flexible, high-performance nanogenerators (NGs). An enhanced power density in the membrane NG is observed with the best-performing device showing a power density of 7.99 mW m-2 compared to 1.04 µW m-2 in bulk Mn3O4. A sensitivity of 108 mV kPa-1 for applied forces <10 N in the membrane NG is observed. The improved performance of these NGs is attributed to enhanced flexoelectric response in a few layers of Mn3O4. Using first-principles calculations, the flexoelectric coefficients of monolayer and bilayer Mn3O4 are found to be 50-100 times larger than other 2D transition metal dichalcogenides (TMDCs). Using a model based on classical beam theory, an increasing activation of the bending mode with decreasing thickness of the oxide membranes is observed, which in turn leads to a large flexoelectric response. As a proof-of-concept, flexible NGs using exfoliated Mn3O4 membranes are made and used in self-powered paper-based devices. This research paves the way for the exploration of few-layered membranes of other centrosymmetric oxides for application as energy harvesters.

Lead-Free Piezoelectric Energy Harvester Based on 2D Bismuth Titanate.

The use of two-dimensional (2D) layered materials with a noncentrosymmetric structure dramatically increases the potential of nanoscale electromechanical systems and electronic devices. In this work, liquid-phase exfoliation of bulk bismuth titanate was employed to synthesize atomically thin 2D sheets and fabricate a high-performance piezoelectric energy harvester. The structural and morphological properties of the 2D sheets were analyzed, confirming their phase purity and layer formation. Piezoelectric properties of the 2D sheets were evaluated using Piezoresponse Force Microscopy (PFM), demonstrating a high d33 piezoelectric coefficient of 40 pm/V in a few-layer bismuth titanate nanosheet. A prototype energy harvesting device was fabricated with 2D bismuth titanate as the active material. The piezoelectric response of the fabricated device was recorded at different frequencies and forces, which yielded a maximum d33 of 57.8 pC/N at 1 Hz. Such a solid electromechanical performance at a relatively infinitesimal input response indicates that 2D bismuth titanate can be useful for piezoelectric energy harvesting applications.

Utilization of DNA and 2D metal oxide interaction for an optical biosensor.

The efficient monitoring and early detection of viruses may provide essential information about diseases. In this work, we have highlighted the interaction between DNA and a two-dimensional (2D) metal oxide for developing biosensors for further detection of viral infections. Spectroscopic measurements have been used to probe the efficient interactions between single-stranded DNA (ssDNA) and the 2D metal oxide and make them ideal candidates for detecting viral infections. We have also used fully atomistic molecular dynamics (MD) simulation to give a microscopic understanding of the experimentally observed ssDNA-metal oxide interaction. The adsorption of ssDNA on the inorganic surface was found to be driven by favourable enthalpy change, and 5'-guanine was identified as the interacting nucleotide base. Additionally, the in silico assessment of the conformational changes of the ssDNA chain during the adsorption process was also performed in a quantitative manner. Finally, we comment on the practical implications of these developments for sensing that could help design advanced systems for preventing virus-related pandemics.

Low bandgap high entropy alloy for visible light-assisted photocatalytic degradation of pharmaceutically active compounds: Performance assessment and mechanistic insights.

The incessant accumulation of pharmaceutically active compounds (PhACs) in various environmental compartments represents a global menace. Herein, an equimolar high entropy alloy (HEA), i.e., FeCoNiCuZn, is synthesized via a facile and scalable method, and its effectiveness in eliminating four different PhACs from aqueous matrices is rigorously examined. Attributing to its relatively low bandgap and multielement active sites, the as-synthesized quinary HEA demonstrates more pronounced photocatalytic decomposition efficiency, towards tetracycline (86%), sulfamethoxazole (94%), ibuprofen (80%), and diclofenac (99%), than conventional semiconductor-based photocatalysts, under visible light irradiation. Additionally, radical trapping assays are conducted, and the dissociation intermediates are identified, to probe the plausible photocatalytic degradation pathways. Further, the end-products of FeCoNiCuZn-mediated photocatalysis are apparently non-toxic, and the HEA can be successfully recycled repeatedly, with no obvious leaching of heavy metal ions. Overall, the findings of this study testify the applicability of FeCoNiCuZn as a visible light-active photocatalyst, for treating wastewaters contaminated with PhACs.

Prospective applications of two-dimensional materials beyond laboratory frontiers: A review.

The development of nanotechnology has been advancing for decades and gained acceleration in the 21st century. Two-dimensional (2D) materials are widely available, giving them a wide range of material platforms for technological study and the advancement of atomic-level applications. The design and application of 2D materials are discussed in this review. In order to evaluate the performance of 2D materials, which might lead to greater applications benefiting the electrical and electronics sectors as well as society, the future paradigm of 2D materials needs to be visualized. The development of 2D hybrid materials with better characteristics that will help industry and society at large is anticipated to result from intensive research in 2D materials. This enhanced evaluation might open new opportunities for the synthesis of 2D materials and the creation of devices that are more effective than traditional ones in various sectors of application.

Dimensionality effects of g-C3N4 from wettability to solar light assisted self-cleaning and electrocatalytic oxygen evolution reaction.

Unique interfacial properties of 2D materials make them more functional than their bulk counterparts in a catalytic application. In the present study, bulk and 2D graphitic carbon nitride nanosheet (bulk g-C3N4 and 2D-g-C3N4 NS) coated cotton fabrics and nickel foam electrode interfaces have been applied for solar light-driven self-cleaning of methyl orange (MO) dye and electrocatalytic oxygen evolution reaction (OER), respectively. Compared to bulk, 2D-g-C3N4 coated interfaces show higher surface roughness (1.094 > 0.803) and enhanced hydrophilicity (θ âˆ¼ 32° < 62° for cotton fabric and θ âˆ¼ 25° < 54° for Ni foam substrate) due to oxygen defect induction as confirmed from morphological (HR-TEM and AFM) and interfacial (XPS) characterizations. The self-remediation efficiencies for blank and bulk/2D-g-C3N4 coated cotton fabrics are estimated through colorimetric absorbance and average intensity changes. The self-cleaning efficiency for 2D-g-C3N4 NS coated cotton fabric is 87%, whereas the blank and bulk-coated fabric show 31% and 52% efficiency. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis determines the reaction intermediates for MO cleaning. 2D-g-C3N4 shows lower overpotential (108 mV) and onset potential (1.30 V) vs. RHE for 10 mA cm-2 OER current density in 0.1 M KOH. Also, the decreased charge transfer resistance (RCT = 12 Ω) and lower Tafel's slope (24 mV dec-1) of 2D-g-C3N4 make it the most efficient OER catalyst over bulk-g-C3N4 and state-of-the-art material RuO2. The pseudocapacitance behavior of OER governs the kinetics of electrode-electrolyte interaction through the electrical double layer (EDL) mechanism. The 2D electrocatalyst demonstrates long-term stability (retention ∼94%) and efficacy compared to commercial electrocatalysts.

Energy harvesting from radio waves using few-layer 2D galena (galenene).

Radiofrequency (RF) energy harvesting is receiving increased attention in today's digital era due to its potential to replace or improve the longevity of energy storage devices in low-power IoT devices. RF energy is available in the ambient environment, but efficient devices are still not commonly known for RF energy harvesting applications. Here, the main goal is to develop an RF energy harvesting device using multi-layered two-dimensional (2D) galena (PbS). A Schottky diode is fabricated by using 2D galena. RF energy harvesting is demonstrated using a handheld radio transceiver with a carrier frequency of 140-170 MHz. The device extracts RF energy and produces an output DC voltage of a maximum of 1.8 volts and a corresponding output power of 38 mW at 150 MHz, and lights up an LED within a range of 100 cm. At 150 MHz, the device's power conversion efficiency is found to be 19%. DFT calculations support the experimental observations of energy harvesting using 2D galena. The performance results show that 2D galena is a promising material for RF energy harvesting devices.

An efficient transition metal chalcogenide sensor for monitoring respiratory alkalosis.

For many biomedical applications, high-precision CO2 detection with a rapid response is essential. Due to the superior surface-active characteristics, 2D materials are particularly crucial for electrochemical sensors. The liquid phase exfoliation method of 2D Co2Te3 production is used to achieve the electrochemical sensing of CO2. The Co2Te3 electrode performs better than other CO2 detectors in terms of linearity, low detection limit, and high sensitivity. The outstanding physical characteristics of the electrocatalyst, including its large specific surface area, quick electron transport, and presence of a surface charge, can be credited for its extraordinary electrocatalytic activity. More importantly, the suggested electrochemical sensor has great repeatability, strong stability, and outstanding selectivity. Additionally, the electrochemical sensor based on Co2Te3 could be used to monitor respiratory alkalosis. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03497-z.

3D Printing of a Biocompatible Nanoink Derived from Waste Animal Bones.

Direct ink writing (DIW) additive manufacturing is a versatile 3D printing technique for a broad range of materials. DIW can print a variety of materials provided that the ink is well-engineered with appropriate rheological properties. DIW could be an ideal technique in tissue engineering to repair and regenerate deformed or missing organs or tissues, for example, bone and tooth fracture that is a common problem that needs surgeon attention. A critical criterion in tissue engineering is that inserts must be compatible with their surrounding environment. Chemically produced calcium-rich materials are dominant in this application, especially for bone-related applications. These materials may be toxic leading to a rejection by the body that may need secondary surgery to repair. On the other hand, there is an abundance of biowaste building blocks that can be used for grafting with little adverse effect on the body. In this work, we report a bioderived ink made entirely of calcium derived from waste animal bones using a benign process. Calcium nanoparticles are extracted from the bones and the ink prepared by mixing with different biocompatible binders. The ink is used to print scaffolds with controlled porosity that allows better growth of cells. DIW printed parts show better mechanical properties and biocompatibility that are important for the grafting application. Degradation tests and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay study were done to examine the biocompatibility of the extracted materials. In addition, discrete element modeling and computational fluid dynamics numerical methods are used in Rocky and Ansys software programs. This work shows that biowaste materials if well-engineered can be a never-ending source of raw materials for advanced application in orthopedic grafting.

Vacancy-Mediated Anomalous Emission Characteristics of Size-Confined Semiconducting CoTe2.

Transition-metal tellurides (TMTs) are promising materials for "post-graphene age" nanoelectronics and energy storage applications owing to their industry-standard compatibility, high electron mobility, large spin-orbit coupling (SOC), etc. However, tellurium (Te) having a larger ionic radius (Z = 52) and broader d-bands endows TMTs with semimetallic nature, restricting their application in photonic and optoelectronic domains. In this work, we report the optical properties of the quantum-confined semiconducting phase of cobalt ditelluride (CoTe2) for the first time, exhibiting excellent two-color band photoabsorption attributes covering the UV-visible and near-infrared regions. Furthermore, novel excitonic resonances (X) of size-varying CoTe2 nanocrystals and quantum dots (QDs) are indicated by their temperature-dependent emission characteristics, which are attributed to the splitting of band edge states via confinement. On the other hand, the sudden rupture of the large-area CoTe2 nanosheets via ultrasonication incorporates Co vacancy-mediated localized trap states within the band gap, which is attributed to the superior room-temperature photoluminescence (PL) quantum yield of QDs and further corroborated using Raman analysis and atomistic density functional theory (DFT) simulations. Most interestingly, the excitonic peak of CoTe2 QDs reveals a unique positive-to-negative thermal quenching transition phenomenon, owing to the thermal activation of nonradiative surface trap states. These results introduce an exciting approach for the defect-mediated color-saturated light emission that paves the way for solution-processed telluride-based QD light-emitting diodes.

Identification of aggregated 2D cobalt tellurides using a spatial self-phase modulation technique.

We report a previously unreported application of the spatial self-phase modulation (SSPM) technique for recognizing solute-solvent interaction in a suspension of 2D material. Broadband optical absorption of the 2D Co2Te3 leads to a nonlinear optical (NLO) susceptibility for the monolayer, i.e., χ M o n o(3) of 1.5 ×10-9 (3.3 ×10-9) esu at 532 (632) nm, which is 1-2 orders higher than for the 2D CoTe and CoTe2. The fine structure of the SSPM patterns is analyzed to explore the foundations of the observed NLO effects. With increasing polarity of the liquid media, a change of 2D Co2Te3 from homophonous dispersion to aggregation occurs, as confirmed from in situ optical microscopy and UV-vis absorption spectroscopy. As a result, type-I (thickest outer ring) SSPM ring patterns are converted to type-II (thinnest outer ring) SSPM ring patterns. Therefore, using SSPM with a CW laser as an optical tool to identify solvent-polarity-induced aggregation in 2D materials is possible.

Synthesis and Characterization of Biotene: A New 2D Natural Oxide From Biotite.

In this work, the synthesis and characterization of ultrathin metal oxide, called biotene, using liquid-phase exfoliation from naturally abundant biotite are demonstrated. The atomically thin biotene is used for energy harvesting using its flexoelectric response under multiple bending. The effective flexoelectric response increases due to the presence of surface charges, and the voltage increases up to ≈8 V, with a high mechano-sensitivity of 0.79 V N-1 for normal force. This flexoelectric response is further validated by density functional theory (DFT) simulations. The atomically thin biotene shows an increased response in the magnetic field and thermal heating. The synthesis of two-dimensional (2D) metal-oxide biotene suggests a wealth of future 2D-oxide material for energy generation and energy harvesting applications.