Recent advances in graphene-based phase change composites for thermal energy storage and management

Energy storage and conservation are receiving increased attention due to rising global energy demands.Therefore,the development of energy storage materials is crucial.Thermal energy storage(TES)systems based on phase change materials(PCMs)have increased in prominence over the past two decades,not only because of their outstanding heat storage capacities but also their superior thermal energy regulation capability.However,issues such as leakage and low thermal conductivity limit their applicability in a variety of settings.Carbon-based materials such as graphene and its derivatives can be utilized to surmount these obstacles.This study examines the recent advancements in graphene-based phase change composites(PCCs),where graphene-based nanostructures such as graphene,graphene oxide(GO),functionalized graphene/GO,and graphene aerogel(GA)are incorporated into PCMs to substantially enhance their shape stability and thermal conductivity that could be translated to better storage capacity,durability,and temperature response,thus boosting their attractiveness for TES systems.In addition,the applications of these graphene-based PCCs in various TES disciplines,such as energy conservation in buildings,solar utilization,and battery thermal management,are discussed and summarized.

Wax from Pyrolysis of Waste Plastics as a Potential Source of Phase Change Material for Thermal Energy Storage

Over the past half-century, plastic consumption has grown rapidly due to its versatility, low cost, and unrivaled functional properties. Among the diff erent implemented strategies for recycling waste plastics, pyrolysis is deemed the most economical option. Currently, the wax obtained from the pyrolysis of waste plastics is mainly used as a feedstock to manufacture chemicals and fuels or added to asphalt for pavement construction, with no other applications of wax being reported. Herein, the thermal pyrolysis of three common waste polyolefin plastics: high-density polyethylene(HDPE), low-density polyethylene(LDPE), and polypropylene(PP), was conducted at 450 ℃. The waste plastics-derived waxes were characterized and studied for a potential new application: phase change materials(PCMs) for thermal energy storage(TES). Gas chromatography–mass spectrometry analysis showed that paraffin makes up most of the composition of HDPE and LDPE waxes, whereas PP wax contains a mixture of naphthene, isoparaffin, olefin, and paraffin. Diff erential scanning calorimetry(DSC) analysis indicated that HDPE and LDPE waxes have a peak melting temperature of 33.8 ℃ and 40.3 ℃, with a relatively high latent heat of 103.2 J/g and 88.3 J/g, respectively, whereas the PP wax was found to have almost negligible latent heat. Fourier transform infrared spectroscopy and DSC results revealed good chemical and thermal stability of HDPE and LDPE waxes after 100 cycles of thermal cycling. Performance evaluation of the waxes was also conducted using a thermal storage pad to understand their thermoregulation characteristics for TES applications.

ZIF-Mediated Anchoring of Co species on N-doped Carbon Nanorods as an Efficient Cathode Catalyst for Zn-Air Batteries

Developing efficient oxygen reduction reaction(ORR)catalyst is essential for the practical application of Zn-air batteries(ZABs).In this contribution,we develop a novel zeolitic imidazolate framework(ZIF)-mediated strategy to anchor Co species on N-doped carbon nanorods for efficient ORR.Featuring ultrahigh N-doping(10.29 at.%),monodisperse Co nanocrystal decoration,and well-dispersed Co-N_(x)functionalization,the obtained Co-decorated N-doped carbon nanorods(Co@NCNR)exhibit a decent ORR performance comparable to commercial Pt/C in alkaline media.Aqueous ZABs have been assembled using Co@NCNR as the cathode catalyst.The assembled ZABs manifest high initial open-circuit voltage as well as high energy density.In addition,the Co@NCNR also demonstrates ideal ORR performance in quasi-solid-state ZABs.

Bottom-Up Engineering Strategies for High-Performance Thermoelectric Materials

The recent advancements in thermoelectric materials are largely credited to two factors,namely established physical theories and advanced materials engineering methods.The developments in the physical theories have come a long way from the“phonon glass electron crystal”paradigm to the more recent band convergence and nanostructuring,which consequently results in drastic improvement in the thermoelectric figure of merit value.On the other hand,the progresses in materials fabrication methods and processing technologies have enabled the discovery of new physical mechanisms,hence further facilitating the emergence of high-performance thermoelectric materials.In recent years,many comprehensive review articles are focused on various aspects of thermoelectrics ranging from thermoelectric materials,physical mechanisms and materials process techniques in particular with emphasis on solid state reactions.While bottom-up approaches to obtain thermoelectric materials have widely been employed in thermoelectrics,comprehensive reviews on summarizing such methods are still rare.In this review,we will outline a variety of bottom-up strategies for preparing high-performance thermoelectric materials.In addition,state-of-art,challenges and future opportunities in this domain will be commented.

Enhancement of current density using effective membranes electrode assemblies for water electrolyser system

The goal of this study was to develop and design a composite proton exchange membrane（PEM） and membrane electrode assembly（MEA） that are suitable for the PEM based water electrolysis system. In particular,it focuses on the development of sulphonated polyether ether ketone（SPEEK） based membranes and caesium salt of silico-tungstic acid（Cs Si WA） matrix compared with one of the transition metal oxides such as titanium dioxide（TiO2）, silicon dioxide（SiO2） and zirconium dioxide（ZrO2）. The resultant membranes have been characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, ion exchange capacity（IEC）, water uptake and atomic force microscopy. Comparative studies on the performance of MEAs were also conducted utilizing impregnation-reduction and conventional brush coating methods. The PEM electrolysis performance of SPEEK-Cs Si WA-ZrO2 composite membrane was more superior than that of other membranes involved in this study. Electrochemical characterization shows that a maximum current density of 1.4 A/cm^2 was achieved at 60 °C, explained by an increased concentration of protonic sites available at the interface.

Insight into the structure-capacity relationship in biomass derived carbon for high-performance sodium-ion batteries

Carbonaceous materials are the most promising candidates as the anode for sodium-ion batteries (SIBs), however, they still suffer from low electric conductivity and sluggish sodium ion (Na+) reaction kinetics. Appropriate composition modulation using heteroatoms doping and structure optimization is highly desired. A basic empirical understanding of the structure-capacity relationship is also urgent in tackling the above problems. Herein, multi-functional nitrogen (N) doped carbon micro-rods with enlarged interlayer spacing are synthesized and investigated as the anode in SIBs, showing an ultra-stable capacity of 161.5 mAh g^(−1) at 2 A g^(−1) for over 5000 cycles. Experimental investigations and first-principle calculations indicate that the enlarged interlayer spacing can facilitate Na+ intercalation and N doping can guarantee the high electric conductivity and favorable electrochemical active sites. Additionally, pyridinic N is theoretically proved to be more effective to enhance Na+ adsorption than pyrrolic N due to the lower adsorption energy and stronger binding energy with Na+. Full SIBs show a high capacity and cyclability, making the biomass-derived carbon micro-rods to be a promising anode for practical SIBs applications.

Molecular mechanisms of tumor resistance to PI3K-mTOR-targeted therapy

Deregulation of the phosphatidylinositide 3-kinase(PI3K) and mammalian target of rapamycin(mTOR) signaling pathway occurs frequently in a wide range of human cancers and is a major driving force in tumorigenesis.Thus,small molecules targeting this pathway are under active development as anticancer therapeutics.Although small-molecule inhibitors of the PI3K-mTOR pathway have shown promising clinical efficacy against human cancers,the emergence of drug resistance may limit their success in the clinic.To date,several resistance mechanisms,including both PI3K-dependent and-independent mechanisms,have been described.Here,we summarize the current understanding of resistance mechanisms to PI3K-mTOR inhibitors and discuss potential strategies for overcoming resistance for potential clinical application.

Nutrient supplemented serum-free medium increases cardiomyogenesis efficiency of human pluripotent stem cells

AIM: To development of an improved p38 MAPK inhibitor-based serum-free medium for embryoid body cardiomyocyte differentiation of human pluripotent stem cells. METHODS: Human embryonic stem cells (hESC) differentiated to cardiomyocytes (CM) using a p38 MAPK inhibitor (SB203580) based serum-free medium (SB media). Nutrient supplements known to increase cell viability were added to SB medium. The ability of these supplements to improve cardiomyogenesis was evaluated by measurements of cell viability, total cell count, and the expression of cardiac markers via flow cytometry. An improved medium containing Soy hydrolysate (HySoy) and bovine serum albumin (BSA) (SupSB media) was developed and tested on 2 additional cell lines (H1 and Siu-hiPSC). Characterization of the cardiomyocytes was done by immunohistochemistry, electrophysiology and quantitative real-time reverse transcriptionpolymerase chain reaction. RESULTS: hESC cell line, HES-3, differentiating in SB medium for 16 d resulted in a cardiomyocyte yield of 0.07 ± 0.03 CM/hESC. A new medium (SupSB media) was developed with the addition of HySoy and BSA to SB medium. This medium resulted in 2.6 fold increase in cardiomyocyte yield (0.21 ± 0.08 CM/hESC). The robustness of SupSB medium was further demonstrated using two additional pluripotent cell lines (H1, hESC and Siu1, hiPSC), showing a 15 and 9 fold increase in cardiomyocyte yield respectively. The age (passage number) of the pluripotent cells did not affect the cardiomyocyte yields. Embryoid body (EB) cardiomyocytes formed in SupSB medium expressed canonical cardiac markers (sarcomeric α-actinin, myosin heavy chain and troponin-T) and demonstrated all three major phenotypes: nodal-, atrial- and ventricular-like. Electrophysiological characteristics (maximum diastolic potentials and action potential durations) of cardiomyocytes derived from SB and SupSB media were similar. CONCLUSION: The nutrient supplementation (HySoy and BSA) leads to increase in cell viability, cell yield and cardiac marker expression during cardiomyocyte differentiation, translating to an overall increase in cardiomyocyte yield.

Advances in the design and development of SARS-CoV-2 vaccines

Since the end of 2019,coronavirus disease 2019(COVID-19)caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has spread worldwide.The RNA genome of SARS-CoV-2,which is highly infectious and prone to rapid mutation,encodes both structural and non-structural proteins.Vaccination is currently the only effective method to prevent COVID-19,and structural proteins are critical targets for vaccine development.Currently,many vaccines are in clinical trials or are already on the market.This review highlights ongoing advances in the design of prophylactic or therapeutic vaccines against COVID-19,including viral vector vaccines,DNA vaccines,RNA vaccines,live-attenuated vaccines,inactivated virus vaccines,recombinant protein vaccines and bionic nanoparticle vaccines.In addition to traditional inactivated virus vaccines,some novel vaccines based on viral vectors,nanoscience and synthetic biology also play important roles in combating COVID-19.However,many challenges persist in ongoing clinical trials.

Mesenchymal Stromal Cells Derived from Human Embryonic Stem Cells, Fetal Limb and Bone Marrow Share a Common Phenotype but Are Transcriptionally and Biologically Different

Mesenchymal stromal cells (MSCs) can be obtained from several sources and the significant differences in their properties make it crucial to investigate the differentiation potential of MSCs from different sources to determine the optimal source of MSCs. We investigated if this biological heterogeneity in MSCs from different sources results in different mechanisms for their differentiation. In this study, we compared the gene expression patterns of phenotypically defined MSCs derived from three ontogenically different sources: Embryonic stem cells (hES-MSCs), Fetal limb (Flb-MSCs) and Bone Marrow (BM-MSCs). Differentially expressed genes between differentiated cells and undifferentiated controls were compared across the three MSC sources. We found minimal overlap (5% - 16%) in differentially expressed gene sets among the three sources. Flb-MSCs were similar to BM-MSCs based on differential gene expression patterns. Pathway analysis of the differentially expressed genes using Ingenuity Pathway Analysis (IPA) revealed a large variation in the canonical pathways leading to MSC differentiation. The similar canonical pathways among the three sources were lineage specific. The Flb-MSCs showed maximum overlap of canonical pathways with the BM-MSCs, indicating that the Flb-MSCs are an intermediate source between the less specialised hES-MSC source and the more specialised BM-MSC source. The source specific pathways prove that MSCs from the three ontogenically different sources use different biological pathways to obtain similar differentiation outcomes. Thus our study advocates the understanding of biological pathways to obtain optimal sources of MSCs for various clinical applications.

Recent Advances in Detection of Ochratoxin-A

Ochratoxin-A[7-(L-β-phenylalanylcarbonyl)-carboxyl-5-chloro-8-hydroxy-3,4-dihydro-3R-methyl-isocumarin, OTA] is a common food contaminant mycotoxin that enters the human body through the consumption of improperly stored food products. Upon ingestion, it leads to immuno-suppression and immuno-toxicity. OTA has been known to produce nephrotoxic, teratogenic, and carcinogenic activity (via oxidative DNA damage) in several species. This review introduces potentials of electrochemical biosensor to provide breakthroughs in OTA detection through improved selectivity and sensitivity and also the current approaches for detecting OTA in food products.

High-throughput fabrication of large-scale metasurfaces using electron-beam lithography with SU-8 gratings for multilevel security printing

The field of metasurface research has rapidly developed in the past decade.Electron-beam lithography(EBL)is an excellent tool used for rapid prototyping of metasurfaces.However,Gaussian-beam EBL generally struggles with low throughput.In conjunction with the recent rise of interest in metasurfaces made of low-index dielectric materials,we propose in this study the use of a relatively unexplored chemically amplified resist,SU-8 with EBL,as a method for rapid prototyping of low-index metasurfaces.We demonstrate the use of SU-8 grating on silicon for cost-efficient fabrication of an all-dielectric multilevel security print for anti-counterfeiting purposes,which encrypt different optical information with different light illumination conditions,namely,bright-field reflection,dark-field reflection,and cross-polarized reflection.The large-scale print(1 mm^(2))could be exposed in a relatively short time(~11 min)due to the ultrahigh sensitivity of the resist,while the feature size of~200 nm was maintained,demonstrating that SU-8 EBL resist serves as a good candidate for rapid prototyping of metasurface designs.Our results could find applications in the general area of increasing EBL patterning speed for a variety of other devices and structures.

Alleviating mechanical degradation of hexacyanoferrate via strain locking during Na^(+) insertion/extraction for full sodium ion battery

Generation of large strains upon Na^(+) intercalation is one of the prime concerns of the mechanical degradation of Prussian blue(PB)and its analogs.Structural construction from the atomic level is imperative to maintain structural stability and ameliorate the long-term stability of PB.Herein,an inter nickel hexacyanoferrate(NNiFCN)is successfully introduced at the out layer of iron hexacyanoferrate(NFFCN)through ion exchange to improve structural stability through compressive stress locking by forming NNiFCN shell.Furthermore,the kinetics of sodium ion diffusion is enhanced through the built-in electric pathway.The electrochemical performance is therefore significantly improved with a remarkable long-term cycling stability over 3,000 cycles at 500 mA·g^(–1) in the full sodium-ion batteries(SIBs)with a maximum energy density of 91.94 Wh·g^(–1),indicating that the core-shell structured NNiFCN/NFFCN could be the low-cost and high-performance cathode for full SIBs in large-scale EES applications.

Metasurface-based subtractive color filter fabricated on a 12-inch glass wafer using a CMOS platform

Optical color filters are widely applied in many areas including display,imaging,sensing,holography,energy harvest,and measurement.Traditional dye-based color filters have drawbacks such as environmental hazards and instability under high temperature and ultraviolet radiation.With advances in nanotechnology,structural color filters,which are based on the interaction of light with designed nanostructures,are able to overcome the drawbacks.Also,it is possible to fabricate structural color filters using standard complementary metal-oxide-semiconductor(CMOS)fabrication facilities with low cost and high volume.In this work,metasurface-based subtractive color filters(SCFs)are demonstrated on 12-inch(300-mm)glass wafers using a CMOS-compatible fabrication process.In order to make the transmissive-type SCF on a transparent glass wafer,an in-house developed layer transfer process is used to solve the glass wafer handling issue in fabrication tools.Three different heights of embedded silicon nanopillars(110,170,and 230 nm)are found to support magnetic dipole resonances.With pillar height and pitch variation,SCFs with different displayed colors are achieved.Based on the resonance wavelength,the displayed color of the metasurface is verified within the red-yellow-blue color wheel.The simulation and measurement results are compared and discussed.The work provides an alternative design for high efficiency color filters on a CMOS-compatible platform,and paves the way towards mass-producible large-area metasurfaces.

Synergistic Effect of Carbon Nanotubes and Layered Double Hydroxides on the Mechanical Reinforcement of Nylon-6 Nanocomposites

Synergistic effect in network formation of nylon-6 （PA6） nanocomposites containing one dimensional （ID） multi-walled carbon nanotubes （CNTs） and two dimensional （2D） layered double hydroxide （LDH） platelets on improving the mechanical properties has been studied. Mechanical tests show that, with incorporation of 1 wt% LDHs and 0.5 wt% CNTs, the tensile modulus, the yield strength as well as the hardness of the ternary composite are greatly improved by about 230%, 128% and 110% respectively, as compared with neat PA6. This is mainly attributed to the unique, strong interactions between the CNTs and the LDHs as well as the jammed network-like structure thus formed between the nanofillers, as confirmed by the morphological observations. As compared with the binary nanocomposites, a much enhanced solid-like behavior in the terminal region of the rheological curves can clearly be observed for the ternary system, which also indicates the formation of a percolating filler network.

Silicon substrate-integrated hollow waveguide for miniaturized optical gas sensing

Gas sensors have a wide variety of applications.Among various existing gas sensing technologies,optical gas sensors have outstanding advantages.The development of the Internet of Things and consumer electronics has put stringent requirements on miniaturized gas sensing technology.Here,we demonstrate a chip-scale silicon substrate-integrated hollow waveguide(Si-iHWG) to serve as an optical channel and gas cell in an optical gas sensor.It is fabricated through silicon wafer etching and wafer bonding.The Si-i HWG chip is further assembled with an off-chip light source and detector to build a fully functional compact nondispersive infrared(NDIR) CO_(2) sensor.The chip size is 10 mm × 9 mm,and the dimension of the sensor excluding the microcontroller board is 50 mm × 25 mm × 16 mm.This chip solution with compactness,versatility,robustness,and low cost provides a cost-effective platform for miniaturized optical sensing applications ranging from air quality monitoring to con-sumer electronics.

Hypervelocity impact induced shock acoustic emission waves for quantitative damage evaluation using in situ miniaturized piezoelectric sensor network

Manmade debris and natural meteoroids, travelling in the Low Earth Orbit at a speed of several kilometers per second, pose a severe safety concern to the spacecraft in service through the HyperVelocity Impact(HVI). To address this issue, an investigation of shock Acoustic Emission(AE) waves induced by HVI to a downscaled two-layer Whipple shielding structure is performed,to realize a quantitative damage evaluation. Firstly a hybrid numerical model integrating smoothparticle hydrodynamics and finite element is built to obtain the wave response. The projectiles, with various impact velocities and directions, are modelled to impact the shielding structure with different thicknesses. Then experimental validation is carried out with built-in miniaturized piezoelectric sensors to in situ sense the HVI-induced AE waves. A quantitative agreement is obtained between numerical and experimental results, demonstrating the correctness of the hybrid model and facilitating the explanation of obtained AE signals in experiment. Based on the understanding of HVI-induced wave components, assessment of the damage severity, i.e., whether the outer shielding layer is perforated or not, is performed using the energy ratio between the regions of ‘‘high frequency" and ‘‘low frequency" in the acquired AE signals. Lastly, the direct-arrival fundamentalsymmetric wave mode is isolated from each sensing signal to be input into an enhanced delay-andsum algorithm, which visualizes HVI spots accurately and instantaneously with different sensor network configuration. All these works demonstrate the potential of quantitative, in situ, and real time HVI monitoring using miniaturized piezoelectric sensor network.

In-plane coherent control of plasmon resonances for plasmonic switching and encoding

Considerable attention has been paid recently to coherent control of plasmon resonances in metadevices for potential applications in all-optical light-with-light signal modulation and image processing.Previous reports based on out-ofplane coherent control of plasmon resonances were established by modulating the position of a metadevice in standing waves.Here we show that destructive and constructive absorption can be realized in metallic nano-antennas through in-plane coherent control of plasmon resonances,which is determined by the distribution rule of electricalfield components of nano-antennas.We provide proof-of-principle demonstrations of plasmonic switching effects in a gold nanodisk monomer and dimer,and propose a plasmonic encoding strategy in a gold nanodisk chain.In-plane coherent control of plasmon resonances may open a new avenue toward promising applications in optical spectral enhancement,imaging,nanolasing,and optical communication in nanocircuits.

Construction of a hierarchical multiscale conducting network for enhanced thermoelectric response in organic PEDOT:PSS based nanocomposites

Thermoelectric technology,which is characterized by the interconversion between heat and electricity,is demonstrated as an efficient and environmentally friendly route for thermal energy harvesting and solid-state cooling devices.The pursuit for high-performance room temperature thermoelectric materials is of significant interest.Here,we proposed a design strategy to dramatically improve the thermoelectric response by constructing a hierarchical multiscale conductor network(AgNWs/CNT)in polymer matrix(PEDOT:PSS).At the optimized composition,the highest Seebeck coefficient and electrical conductivity of base treated ternary PEDOT:PSS/AgNWs/CNT composite are optimized to be 58.6μV K^(-1)and~1950 S cm-1.Correspondingly,the power factor is thus calculated to be on the order of 670μV m^(-1)K^(-2),which is among one of the highest values compared with previous reports.The underlying mechanism is illustrated based on detailed structure,morphology and electron transport quantification.This work affords a novel strategy for the future development of high-performance room temperature nanocomposite thermoelectrics.

Empowering magnetic strong coupling and its application for nonlinear refractive index sensing

In the context of quantum strong coupling,the magnetic dipole(MD)emitters are largely overlooked due to the rarity of MD source and the non-magnetic nature of matters at high frequencies.Based on a semi-classic model,we theoretically demonstrate magnetic strong coupling between an MD cluster(Er^(3+):4 I13/2→4 I15/2 transition at 1,550 nm)and an antenna-in-cavity structure.It is found that placing the plasmonic diabolo/s-diabolo nanoantenna,which supports strong electric/magnetic dipole mode,inside a dielectric cavity could largely improve the strong coupling coefficient while suppressing the cavity loss rate compared to the bare nanoantenna counterparts,empowering the magnetic quantum strong coupling at a level of 104 emitters,which is remarkable considering the weak MD dipole momentum and small hotspot region at high frequency.Furthermore,the two Rabi resonance branches undergo highly asymmetrical changes upon a small variation on the environmental refractive index,which leads to an exotic exponential sensitivity profile by tracing the ratio between the two resonances widths.The proposed magnetic strong coupling for nonlinear refractive index sensing may add a new category to quantum plasmonic sensors.