Tunable Function Research Articles

Photonic generation of triangular waveform with tunable symmetry based on channelized frequency synthesis.

A symmetry tunable triangular waveform photonic generator based on channelized frequency synthesis is proposed and studied. The generator adopts a multichannel system architecture and harmonic amplitude control algorithm to physically isolate each subchannel. In a single subchannel, quadrature phase shift keying modulation and coherent dual-wavelength balanced detection are used to realize optical upconversion and suppress mixing interference in the process of frequency conversion. Therefore, the model has the characteristics of a high-order Fourier series fitting tunable function waveform output. The analysis results show that the Fourier series harmonic coefficients can be adjusted flexibly by the multivariable joint regulation algorithm. The relationship between the variables is analyzed and discussed. The feasibility of the scheme is verified by optical simulation; when the rms error (RMSE)≤0.03, a 20%-80% tunable symmetry triangular waveform can be obtained.

Application of Covalent Organic Frameworks in Sulfur‐Based Battery Separators

Owing to the high storage capacity and multiple‐electron‐transfer chemistry of sulfur (S), sulfur‐based (S‐based) batteries with merits of high theoretical capacity/energy density, eco‐friendliness, and abundant supply hold much potential for energy‐storage/conversion devices. The capacity of S‐based batteries is much higher than that of traditional‐metal‐oxide cathode‐based lithium‐ion batteries, which is regarded as the highest capacity of solid‐state cathode materials at the current stage. As a vital component of S‐based batteries, separators play a profound role in resolving urgent issues (e.g., shuttling effect, volume expansion, poor conductivity, and metal dendrites, etc.). So far, some pioneering works have been reported in the exploration of separators for S‐based battery. On this basis, covalent organic frameworks (COFs), as a kind of functional materials, offer much possibility for S‐based battery separators due to their advantages such as high porosity, crystalline and well‐defined structures, designable struts, and tunable functions, etc. Herein, the reported works about COFs in S‐based battery separators including their structural characteristics, preparation methods, application forms, and battery properties are summarized. Moreover, also, a brief perspective is proposed on the challenges of COFs applied in S‐based battery separators, and new insights are provided for scientists in this field.

Simulation studies on MoS2 (n)/a-Si:H (i)/c-Si (p)/MoO3 heterojunction solar cells using one sided short diode approximation

C-Si based heterojunction solar cells with dopant-free electron and hole transport layers (ETL and HTL) have attracted the researcher’s attention due to their high efficiency and relatively less complicated fabrication process. A number of materials have been proposed for their applications, as ETL and HTL. We have chosen n-type MoS2 monolayer as ETLfor c-Si based heterojunction solar cells and optimized the layer parameters, doping and thickness to achieve the efficiency of 21.05% with a Voc of 641 mV and Jsc of 45.88 mA/cm2 when direct metallization of Ag is used at back contact using one sided short diode approximation. Further, withinsertion of MoO3 as HTL at the back before Ag electrode, the efficiency could be improved to 23.54%with proper tuning of work function of MoO3. The increase in efficiency is accompanied with a small increase in Voc (650 mV) and Jsc (46.5 mA/cm2). Our studies provide a pathway to fabricate dopant free c-Si based heterojunction solar cells with comparable efficiency as those for HIT solar cells.

A crystalline carbon nitride-based separator for high-performance lithium metal batteries.

Lithium metal anodes with ultrahigh theoretical capacities are very attractive for assembling high-performance batteries. However, uncontrolled Li dendrite growth strongly retards their practical applications. Different from conventional separator modification strategies that are always focused on functional group tuning or mechanical barrier construction, herein, we propose a crystallinity engineering-related tactic by using the highly crystalline carbon nitride as the separator interlayer to suppress dendrite growth. Interestingly, the presence of Cl- intercalation and high-content pyrrolic-N from molten salt treatment along with highly crystalline structure enhanced the interactions of carbon nitride with Li+ and homogenized lithium flux for uniform deposition, as supported by both experimental and theoretical evidences. The Li-Li cell with the modified separator therefore delivered ultrahigh stability even after 3,000 h with dendrite-free cycled electrodes. Meanwhile, the assembled Li-LiFePO4 full-cell also presented high-capacity retention. This work opens up opportunities for design of functional separators through crystallinity engineering and broadens the use of C3N4 for advanced batteries.

Biomass derived nanoarchitectonics of porous carbon with tunable oxygen functionalities and hierarchical structures and their superior performance in CO2 adsorption and energy storage

Biomass-derived nanoporous carbons (BNCs) are attractive materials for CO2 capture and energy storage due to their unique surface properties and the availability of low-cost and abundant supply of carbon sources. However, the order of the carbon atoms, the nature of the porosity and surface functional groups are critical in dictating the performance of BNCs for such applications. Herein, a solid-phase activation strategy is introduced to prepare O-functionalized BNCs with embedded graphene-like structures using d(+)-glucose as a precursor. The optimised material shows a high surface area (3572 m2 g−1), and surface oxygenated functional groups, which lead to a high CO2 adsorption of 5.28 mmol g−1 at 1 bar and 31.5 mmol g−1 at 30 bar at 0 °C. Moreover, as an electrode material, the optimised sample exhibits an impressive specific capacitance (Cs) of 305 F g-1 at 0.5 A g−1 and 207 F g-1 at 10 A g−1 in a three-electrode supercapacitor. It also shows high specific capacitance (250 F g-1 at 0.5 A g−1), a high energy density (58 Wh/kg), and stable cyclic performance in a two-symmetric electrode system. The presented materials and their application performance results are promising and could pave the way for the development of more sophisticated materials for CO2 capture, energy storage and beyond.

Work function tuning of directly grown graphene via ultraviolet–ozone treatment for electrode application in organic photovoltaic devices

Graphene is an efficient electrode material for flexible optoelectronic devices because of its high transmittance and electrical conductivity. A graphene film directly grown using plasma-enhanced chemical vapor deposition is suitable for electrode applications because it can be prepared on a glass substrate at relatively low temperatures without a transfer process from a metal catalyst. However, to obtain efficient optoelectronic devices using graphene electrodes, surface modification is necessary. Herein, we tuned the work function of a graphene electrode using ultraviolet (UV)-O3 treatment. The power conversion efficiency of organic photovoltaic devices was significantly increased by the UV-O3 treatment of the graphene anode. To investigate the origin of the improved device performance, the interface between the graphene anode and tetraphenyldibenzoperiflanthene (DBP) donor layer was analyzed via in situ ultraviolet photoelectron spectroscopy. The energy offset between the Fermi level of graphene and the highest occupied molecular orbital level of DBP was significantly reduced because of the increased work function. The results indicate that the electronic structure modification of graphene is of significant importance for fabricating efficient optoelectronic devices.

A frequency tunable resonator using liquid crystals on flexible substrates

ABSTRACT Liquid crystals have already been widely used in reconfigurable microwave devices through external electrically controlled dielectric properties. The traditional method is to sandwich liquid crystals between two metal layers etched on hard substrates. However, this method of adding external electric fields tends to cause short-circuiting between the upper and lower electrodes of liquid crystals in the bending state for the case of electrodes on flexible substrates. In this paper, a novel method is proposed to realise a frequency tunable resonator using liquid crystal fabricated on flexible substrates. The resonator is composed of coplanar waveguide structures. Since the metal layers of the coplanar waveguide placed on the same horizontal plane do not touch each other when bending, it allows the controlled electric field direction to be parallel to the electrode layers. Liquid crystals are placed under the coplanar metals for the electric field control. In order to maximise tunability, the structural parameters of the proposed structure were analysed in detail. The test results agree with the theory and simulation to verify the reliability of this frequency tunable resonator. Furthermore, the test results also illustrate that the applied electric field method can achieve the frequency continuous electrically tunable function when the flexible resonator is bending.

Scalable biomimetic sensing system with membrane receptor dual-monolayer probe and graphene transistor arrays.

Affinity-based biosensing can enable point-of-care diagnostics and continuous health monitoring, which commonly follows bottom-up approaches and is inherently constrained by bioprobes' intrinsic properties, batch-to-batch consistency, and stability in biofluids. We present a biomimetic top-down platform to circumvent such difficulties by combining a "dual-monolayer" biorecognition construct with graphene-based field-effect-transistor arrays. The construct adopts redesigned water-soluble membrane receptors as specific sensing units, positioned by two-dimensional crystalline S-layer proteins as dense antifouling linkers guiding their orientations. Hundreds of transistors provide statistical significance from transduced signals. System feasibility was demonstrated with rSbpA-ZZ/CXCR4QTY-Fc combination. Nature-like specific interactions were achieved toward CXCL12 ligand and HIV coat glycoprotein in physiologically relevant concentrations, without notable sensitivity loss in 100% human serum. The construct is regeneratable by acidic buffer, allowing device reuse and functional tuning. The modular and generalizable architecture behaves similarly to natural systems but gives electrical outputs, which enables fabrication of multiplex sensors with tailored receptor panels for designated diagnostic purposes.

Surface engineering of mesoporous-TiO2 electron transport layer for improved performance of organic-inorganic perovskite solar cells via suppressing interface defects, enhancing charge extraction and boosting carrier transport

Organic-inorganic perovskite solar cells (PrSCs) have emerged as a promising solar photovoltaic technology in terms of realizing high power conversion efficiency (PCE). However, their limited lifetime and poor device stability limit their commercialization in future. In this regard, interface engineering of the electron transport layer (ETL) using 2D materials have been currently used owing to their high carrier mobility, high thermal stability and tunable work function which in turn enormously impact the charge carrier dynamics. In this work, we report an easy and effective way of simultaneously enhancing the efficiency and air-stability of PrSCs via interface engineering by incorporating 2D-MoS2 (bi/tri-layered) in mesoporous-titanium dioxide (mp-TiO2) scaffold electron transport buffer layer, and using CVD grown perovskite layers. The PrSCs were fabricated in ambient air conditions in device configuration, FTO/c-TiO2/mp-TiO2:2D-MoS2/CH3NH3PbI3/P3HT/Au, with an active area of 0.16 cm2. The best device using c-TiO2/mp-TiO2:2D-MoS2 (0.5 wt%) ETL exhibited a substantial increase in PCE ∼13.04% as compared to PCE ∼8.75% realized in reference device fabricated without incorporating MoS2 in mp-TiO2 buffer layer. The incorporation of MoS2 nanoflakes in mp-TiO2 ETL not only enhances the PCE to ∼49%, but also improve the lifetime (retaining PCE ∼86% of its initial value up to 500 hrs, without encapsulation). The enhancement in performance of c-TiO2/mp-TiO2:2D-MoS2 ETL based devices as compared with reference c-TiO2/mp-TiO2 ETL based devices is attributed to, (i) reduction in the work function of mp-TiO2 ETL buffer on dispersion of 2D-MoS2 nanoflakes forming of a perfect interface at ETL/perovskite offering extremely less interfacial energy barrier to promote the charge extraction process at the interface, and suppress the surface recombination losses, (ii) fast charge collection as 2D-MoS2 in TiO2 strongly support the electron transport due to their highly crystalline nature, and (iii) lifetime improvement due to better moisture stability of 2D-MoS2 and high quality of chemical vapor grown perovskite thin films. This work presents an efficient mp-TiO2:2D-MoS2 scaffold ETL for realizing high performance, low cost, air-processed PrSCs for their future development.

Amino acid modified Ti3C2Tx as electron transport layers for high-performance organic solar cells

The Ti3C2Tx, as a typical representative of the MXene family, has attracted much attention due to excellent properties in terms of transmittance, conductivity, tunable work function (WF), and low temperature solution processability. However, the work function that needs to be adjusted and a large number of crystal defects in Ti3C2Tx greatly restrict its use in electronic devices. Herein, Ti3C2Tx is modified with amino acids to modulate WF of Ti3C2Tx and passivate its defect sites, thereby improving the electrical properties of Ti3C2Tx and enhancing the performance of organic solar cells (OSCs). Amino acids interact with Ti3C2Tx by charge transfer and forming a surface dipole on the surface, which reduces the WF of Ti3C2Tx. Moreover, -NH2 of amino acids passivates the negatively charged Ti vacancies in Ti3C2Tx, while -COOH of amino acids passivates the positively charged C vacancies, increasing the conductivity of Ti3C2Tx. Consequently, the OSCs with amino acid-modified Ti3C2Tx-based as new electron transport layer (ETL) exhibit more than 18% of power conversion efficiency (PCE) and good device stability. The work shows OSCs with high performance can be fabricated by using environmental-friendly amino acids, which inspires researchers to seek ideas for fabricating efficient devices from natural materials.

Acoustic metalens with switchable and sharp focusing

Sharp and tunable focusing functionality is highly desired in various acoustic application fields. Here, we propose a simply structured metalens for water-borne sounds with a switchable focusing functionality. Each meta-atom in the lens is composed of two elliptical iron cylinders, and is smartly designed so that it can redirect a normally incident plane wave toward the same focal spot. A switchable focusing functionality between a transmissive lens and a reflective one can be achieved by simply rotating the elliptical cylinders. Furthermore, a sharp focusing effect is obtained with a high-intensity concentration ratio along both transverse and longitudinal directions.

Research Advances on 2D Mxenes for Photovoltaic Applications

MXene, a two-dimensional nanomaterial, has an impressive range of properties that make it a perfect choice for a variety of applications, including energy systems, high-tech sensors, optics, medical devices, and electromagnetic interference shielding. Its high carrier mobility, metallic electrical conductivity, superior transparency, excellent mechanical characteristics, and tunable work function have drawn much attention. This review examines the utilization of MXene in solar technology, highlighting its potential as an electrode, charge carrier, and additive in quantum dot-sensitized, perovskite, silicon wafer-based, and organic solar cells. Additionally, a summary table is provided that briefly outlines the different methods of synthesizing MXene and their respective etching chemicals and precursors. This review’s latter part looks at the challenges associated with MXene and offers potential solutions and prospects.

Supramolecular Self-Assembly of Engineered Polyproline Helices.

The ability to rationally design biomaterials to form desired supramolecular constructs presents an ever-growing research field, with many burgeoning works within recent years providing exciting results; however, there exists a broad expanse of promising avenues of research yet to be investigated. As such we have set out to make use of the polyproline helix as a rigid, tunable, and chiral ligand for the rational design and synthesis of supramolecular constructs. In this investigation, we show how an oligoproline tetramer can be specifically designed and functionalized, allowing predictable tuning of supramolecular interactions, to engineer the formation of supramolecular peptide frameworks with varying properties and, consequently, laying the groundwork for further studies utilizing the polyproline helix, with the ability to design desired supramolecular structures containing these peptide building blocks, having tunable structural features and functionalities.

3D-Printed Polylactic Acid/Lignin Films with Great Mechanical Properties and Tunable Functionalities towards Superior UV-Shielding, Haze, and Antioxidant Properties.

Three-dimensional (3D) printing is regarded as a novel technique to realize the customized production of films. However, the relative lack of printable materials with excellent mechanical properties and tailored functionalities seriously restricts its wide application. Herein, a promising multifunctional 3D printing filament was fabricated by incorporating lignin into the polylactic acid (PLA) matrix and firstly applied to film production. The results indicate that lignin was an excellent mechanical reinforcement of the PLA matrix, especially for toughening. Only 0.5% lignin doping improved the toughness by 81.8%. Additionally, 3D-printed films with 0.5-5% lignin exhibited excellent ultraviolet (UV)-blocking capability of 87.4-99.9% for UVB and 65.6-99.8% for UVA, as well as remarkable antioxidant properties, ranging from 24.0% to 79.0%, and high levels of haze, ranging from 63.5% to 92.5%. Moreover, the prepared PLA/lignin (P/L) films based on 3D printing achieved the customization of film production and have potential applications in the fields of packaging, electronic products, medical care, and so forth. Overall, this work not only enriches the 3D printing composites with tailored multifunctionality but also brings the promising potential for the production of customized films.

High single Zn-ion conductive porous organic conductors decorated with dense acidic groups via double post-synthetic sulfonations

Solid Zn-ionic conductors are one of the important components of rechargeable aqueous Zn-ion batteries. Although ion-conductive porous materials have been intensively studied due to their effective conduction pathways through large surface areas and tunable functionalities, porous material-based Zn ion conductors have been rarely reported because the strong electrostatic bonding properties of divalent Zn2+ ions generally lead to slow diffusion rates and low conductivity. Herein, we prepared porous organic polymer (POP)-based Zn-ion conductors via multiple post-synthetic modifications. The porous conductor with a large number of Zn-ion-incorporated sites exhibited a conductivity value of 3.24×10−4 S cm−1, and a transference number of 0.94, which are the highest values among other porous materials. The long-term performance of conductivity was retained for at least one week. This work highlights the remarkable effectiveness of multiple post-synthetic modifications to achieve high Zn-ion conductivity and provides the first demonstration of a Zn-ion POP conductor.

Miniaturized Bloch Surface Wave Platform on a Multicore Fiber

We propose a novel implementation of a miniaturized photonic platform fabricated on a multicore fiber tip, capable of tunable optical functions via coupling to Bloch surface waves (BSWs). A one-dimensional photonic crystal is deposited on the cleaved surface of a fiber tip, allowing the propagation of BSWs in the near-infrared. On top of each core, subwavelength gratings are fabricated to operate as optical couplers between BSWs and the corresponding fiber modes. The ability to control the optical interconnection among different pairs of cores of the multicore fiber via polarization-selective BSW coupling is demonstrated. The resulting compact, tunable, and portable platforms can be fruitfully employed in the vast application domain covered by optical fiber technology including sensing, optical trapping, manipulation, and information processing.

Synthesis, Characterization, and Docking Study of Novel Thioureidophosphonate-Incorporated Silver Nanocomposites as Potent Antibacterial Agents.

Newly synthesized mono- and bis-thioureidophosphonate (MTP and BTP) analogues in eco-friendly conditions were employed as reducing/capping cores for 100, 500, and 1000 mg L-1 of silver nitrate. The physicochemical properties of silver nanocomposites (MTP(BTP)/Ag NCs) were fully elucidated using spectroscopic and microscopic tools. The antibacterial activity of the nanocomposites was screened against six multidrug-resistant pathogenic strains, comparable to ampicillin and ciprofloxacin commercial drugs. The antibacterial performance of BTP was more substantial than MTP, notably with the best minimum inhibitory concentration (MIC) of 0.0781 mg/mL towards Bacillus subtilis, Salmonella typhi, and Pseudomonas aeruginosa. Among all, BTP provided the clearest zone of inhibition (ZOI) of 35 ± 1.00 mm against Salmonella typhi. After the dispersion of silver nanoparticles (AgNPs), MTP/Ag NCs offered dose-dependently distinct advantages over the same nanoparticle with BTP; a more noteworthy decline by 4098 × MIC to 0.1525 × 10-3 mg/mL was recorded for MTP/Ag-1000 against Pseudomonas aeruginosa over BTP/Ag-1000. Towards methicillin-resistant Staphylococcus aureus (MRSA), the as-prepared MTP(BTP)/Ag-1000 displayed superior bactericidal ability in 8 h. Because of the anionic surface of MTP(BTP)/Ag-1000, they could effectively resist MRSA (ATCC-43300) attachment, achieving higher antifouling rates of 42.2 and 34.4% at most optimum dose (5 mg/mL), respectively. The tunable surface work function between MTP and AgNPs promoted the antibiofilm activity of MTP/Ag-1000 by 1.7 fold over BTP/Ag-1000. Lastly, the molecular docking studies affirmed the eminent binding affinity of BTP over MTP-besides the improved binding energy of MTP/Ag NC by 37.8%-towards B. subtilis-2FQT protein. Overall, this study indicates the immense potential of TP/Ag NCs as promising nanoscale antibacterial candidates.

The Unique Light-Harvesting System of the Algal Phycobilisome: Structure, Assembly Components, and Functions.

The phycobilisome (PBS) is the major light-harvesting apparatus in cyanobacteria and red algae. It is a large multi-subunit protein complex of several megadaltons that is found on the stromal side of thylakoid membranes in orderly arrays. Chromophore lyases catalyse the thioether bond between apoproteins and phycobilins of PBSs. Depending on the species, composition, spatial assembly, and, especially, the functional tuning of different phycobiliproteins mediated by linker proteins, PBSs can absorb light between 450 and 650 nm, making them efficient and versatile light-harvesting systems. However, basic research and technological innovations are needed, not only to understand their role in photosynthesis but also to realise the potential applications of PBSs. Crucial components including phycobiliproteins, phycobilins, and lyases together make the PBS an efficient light-harvesting system, and these provide a scheme to explore the heterologous synthesis of PBS. Focusing on these topics, this review describes the essential components needed for PBS assembly, the functional basis of PBS photosynthesis, and the applications of phycobiliproteins. Moreover, key technical challenges for heterologous biosynthesis of phycobiliproteins in chassis cells are discussed.

Reconstructing the cosmological density and velocity fields from redshifted galaxy distributions using V-net

The distribution of matter that is measured through galaxy redshift and peculiar velocity surveys can be harnessed to learn about the physics of dark matter, dark energy, and the nature of gravity. To improve our understanding of the matter of the Universe, we can reconstruct the full density and velocity fields from the galaxies that act as tracer particles. In this paper, we usethe simulated halos as proxies for the galaxies. We use a convolutional neural network, a V-net, trained on numerical simulations of structure formation to reconstruct the density and velocity fields. We find that, with detailed tuning of the loss function, the V-net could produce better fits to the density field in the high-density and low-density regions, and improved predictions for the probability distribution of the amplitudes of the velocities. However, the weights will reduce the precision of the estimated β parameter. We also find that the redshift-space distortions of the halo catalogue do not significantly contaminate the reconstructed real-space density and velocity field. We estimate the velocity field β parameter by comparing the peculiar velocities of halo catalogues to the reconstructed velocity fields, and find the estimated β values agree with the fiducial value at the 68% confidence level.

Production of nanocellulose using controlled acid hydrolysis from large-scale production of micro-fibrillated cellulose derived from oil palm empty fruit bunches

Nanocellulose is generally known as a versatile material, which is suitable for various applications due to its unique physicochemical properties, including light weight, ease of tunable surface functionalization, and excellent mechanical properties. This research aims to characterize and synthesize nanocellulose produced from acid hydrolysis of large-scaled micro-fibrillated cellulose (MFC) derived from oil palm empty fruit bunches by varying concentrations of H2SO4 from 20 to 35 v/v %. The obtained large-scaled MFC had a density of 1.01 kg/m3 and was dominantly composed of 71% cellulose. After acid hydrolysis of MFC, there were gradual changes in the colour of the obtained cellulose nanocrystals (CNC) dispersion from light white to a darker color with the increase of acid concentration, in which the over hydrolysis occurs at 35% of acid concentration. The use of 25-30% H2SO4 showed the optimum condition to avoid over-hydrolysis and resulted in bright white color of CNC dispersion with excellent stability at zeta potential value of -74.2±0.1 to -88.4±0.2 mV. It was supported by Fourier transform infrared (FTIR) due to the presence of negatively charged sulfonyl and hydroxyl groups upon CNC formation to offer excellent dispersion stability. Based on transmission electron microscope (TEM), rod-like shape CNC with a low aspect ratio of 11.8 at the dimension of 12.8 ± 6.7 nm in width and 151.9 ± 38.3 nm in length was successfully produced. Based on X-ray diffraction (XRD) analysis, the crystallinity of the sample was 76%.