Structure and electrochemical performance of delafossite AgFeO_(2)nanoparticles for supercapacitor electrodes

Delafossite AgFeO_(2)nanoparticles with a mixture of 2H and 3R phases were successfully fabricated by using a simple co-precipitation method.The resulting precursor was calcined at temperatures of 100,200,300,400,and 500℃to obtain the delafossite AgFe0_(2)phase.The morphology and microstructure of the prepared AgFeO_(2)samples were characterized by using field emission scanning electron microscopy(FESEM),transmission electron microscopy(TEM),N_(2) adsorption/desorption,X-ray absorption spectroscopy(XAS),and Xray photoelectron spectroscopy(XPS)techniques.A three-electrode system was employed to investigate the electrochemical properties of the delafossite AgFeO_(2)nanoparticles in a 3 M KOH electrolyte.The delafossite AgFeO_(2)nanoparticles calcined at 100℃(AFO100)exhibited the highest surface area of 28.02 m^(2)·g^(-1)and outstanding electrochemical performance with specific capacitances of 229.71 F·g^(-1)at a current density of 1 A·g^(-1)and 358.32 F·g^(-1)at a scan rate of 2 mV·s^(-1).This sample also demonstrated the capacitance retention of 82.99% after 1000 charge/discharge cycles,along with superior specific power and specific energy values of 797.46 W·kg^(-1)and 72.74Wh·kg^(-1),respectively.These findings indicate that delafossite AgFeO_(2)has great potential as an electrode material for supercapacitor applications.

Dynamic phase transition behavior of a LiMn_(0.5)Fe_(0.5)PO_(4) olivine cathode material for lithium-ion batteries revealed through in-situ X-ray techniques

LiMn_(0.5)Fe_(0.5)PO_(4) has attracted great interest due to its good electrochemical performance and higher operating voltages.This has led to a greater than 30 percent higher energy density than for commercial Li Fe PO4 olivine cathodes.Understanding the phase transition behaviors and kinetics of this material will help researchers to design and develop next generation cathodes for Li-ion batteries.In this study,we investigated non-equilibrium phase transition behaviors in a LiMn_(0.5)Fe_(0.5)PO_(4) cathode material during charge–discharge processes by varying current rates(C-rates)using synchrotron in-situ X-ray techniques.These methods included wide angle X-ray scattering(in-situ WAXS)and X-ray absorption spectroscopy(in-situ XAS).The WAXS spectra indicate that the phase transition of LiMn_(0.5)Fe_(0.5)PO_(4) material at slow C-rates is induced by a two-phase reaction.In contrast,at a high C-rate(5 C),the formation of an intermediate phase upon discharge is clearly observed.Concurrently,the oxidation numbers of the redox reactions of Fe^(2+)/Fe^(3+)and Mn^(2+)/Mn^(3+)were evaluated using in-situ XAS.This combination of synchrotron in-situ X-ray techniques gives clear insights into the non-equilibrium phase transition behavior of a LiMn_(0.5)Fe_(0.5)PO_(4) cathode material.This new understanding will be useful for further developments of this highly promising cathode material for practical commercialization.

Synergistic anticancer effect of the extracts from Polyalthia evecta caused apoptosis in human hepatoma(HepG2)cells

Objective:To evaluate the anticancer activity of the extract fraction of Polyalthia evecta(P. evecta)(Pierre) Finet & Gagnep and the synergistic anticancer effect of the extracts from P.evecta by using the ATR/FT-IR spectroscopy.Methods:The 50%ethanol-water crude leaf extract of P.evecta(EW-L) was prepared and was further fractionated to isolate various fractions.The anticancer activity was investigated from cytotoxicity against HepG2 using a neutral red assay and apoptosis induction by evaluation of nuclei morphological changes after DAPI staining. Synergistic anticancer effects of the extracts from P.evecta were performed using the ATR/FTIR spectroscopy.Results:The result showed that the EW-L showed higher cytotoxicity and apoptosis induction in HepG2 cells than its fractionated extracts.The hexane extract exhibited higher cytotoxicity and apoptosis induction than the water extracts,but less than the EW-L. The combined water and hexane extracts apparently increased cytotoxicity and apoptosis induction.The%apoptotic cells induced by the extract mixture were increased about 2-fold compared to the single hexane extract Conclusions:The polar extract fraction is necessary for the anticancer activity of the non-polar extract fraction.The ATR/FT-IR spectra illustrates the physical interaction among the constituents in the extract mixture and reveals the presence of polyphenolic constituents in the EW-L,which might play a role for the synergistic anticancer effect.

Sulforaphene in Raphanus sativus L. var. caudatus Alef increased in late-bolting stage as well as anticancer activity

Objectives: To evaluate the concentration differences of sulforaphene and sulforaphane at various ages and in different parts of Raphanus sativus L. var. caudatus with respect to their potential cancer preventive effect on HCT116 colon cancer cells.Methods: FTIR–ATR and GC–MS were used to characterize the isothiocyanates in the plant extracts followed by HPLC for quantification. Antiproliferation and apoptosis induction were determined by using MTT assay and flow cytometry, respectively.Results: The respective rank of anticancer activity of Raphanus sativus were as follows:vegetative(3 week) < older rosette(4 week) < early-bolting(5 week) < senescence(7 week) < late-bolting(6 week). The low to high concentration of sulforaphene and sulforaphane occurred in the same stage order.Conclusions: The reproductive parts(flower, pod, and dry seed) of Raphanus sativus have the greatest isothiocyanate concentration, evidenced by a sulforaphene concentration higher than the sulforaphane. This result should inform the selection of the most appropriate harvesting stage and plant part for use as a potential chemopreventive agent.

Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

Synthesis, characterization and magnetic properties of KFeO_(2) nanoparticles prepared by a simple egg white solution route

Nanoparticles of potassium ferrite(KFeO_(2))in this work were synthesized by a simple egg white solution method upon calcination in air at 773,873,and 973 K for 2 h.The effects of calcination temperature on the structural and magnetic properties of the synthesized KFeO_(2) nanoparticles were investigated.By varying the calcination temperature,X-ray diffraction and transmission electron microscopy results indicated the changes in crystallinity and morphology including particle size,respectively.Notably,the reduction in particle size of the synthesized KFeO_(2) was found to have a remarkable influence on the magnetic properties.At room temperature,the synthesized KFeO_(2) nanoparticles prepared at 873 K exhibited the highest saturation magnetization(M_(S))of 2.07×10^(4) A·m^(−1).In addition,the coercivity(H_(C))increased from 3.51 to 16.89 kA·m^(−1) as the calcination temperature increased to 973 K.The zero-field cooled(ZFC)results showed that the blocking temperatures(T_(B))of about 125 and 85 K were observed in the samples calcined at 773 and 873 K,respectively.Therefore,this work showed that the egg white solution method is simple,cost effective,and environmentally friendly for the preparation of KFeO_(2) nanoparticles.

Local Structure Analysis of Lead Zinc Niobate-Barium Titanate Ceramic by X-Ray Absorption Spectroscopy and Density Functional Calculation

The local structure of an alternative Pb（Zn1/3Nb2/3）O3-based perovskite ceramic is investigated. The 0.07BaTiO33-0.93Pb（Zn1/3Nb2/3）O3 ceramic is synthesized using a combination of Zn3Nb2O8 B-site precursor and BaTiO33 perovskite phase stabilizer. Then, x-ray absorption spectroscopy and density functional theory are employed to calculate the local structure configuration and formation energy of the prepared samples. Ba2＋ is found to replace Pb2＋ in AA-site with Zn2＋ occupying BB-site in Pb（Zn1/3Nb2/3）O3, while in the neighboring structure, Ti4＋4＋ replaces Nb5＋5＋ in BB-site with Pb2＋2＋ occupying AA-site. With the substitution of BaTiO33 in Pb（Zn1/3Nb2/3）O3, the bond length between Zn2＋ and Pb2＋ is longer than that of the typical perovskite phase of Pb（Zn1/3Nb2/3）O3. This indicates the key role of BaTiO33 in decreasing the steric hindrance of Pb2＋ lone pair, and the mutual interactions between Pb2＋ lone pair and Zn2＋ and the formation energy is seen to decrease. This finding of the formation energy and local structure configuration relationship can further extend a fundamental understanding of the role of BaTiO33 in stabilizing the perovskite phase in PbZn13Nb23O3-based materials, which in turn will lead to an improved preparation technique for desired electrical properties.

Influence of polymer solution on the morphology and local structure of NH_(4)ZnPO_(4)powders synthesized by a simple precipitation method at room temperature

NH_(4)Zn PO_(4)powders were synthesized using a simple precipitation method at room temperature.The effects of polyvinyl pyrrolidone(PVP),polyvinyl alcohol(PVA),glucose,and hexadecyltrimethylammonium bromide(CTAB)solutions on the morphology and structure of the prepared samples were investigated.The phase composition and morphology of the prepared samples were characterized using X-ray diffraction and scanning electron microscopy,respectively.Depending on the polymer sources,the hexagonal structure prepared using non-surfactant of water completely changed to monoclinic structure when CTAB was added.X-ray absorption near-edge structure(XANES)and X-ray photoelectron spectroscopy(XPS)were performed to study the local structure and surface electronic structure of the prepared samples,confirming that the oxidation states of P and Zn ions are^(5+)and^(2+),respectively.On the basis of the results of inductively coupled plasma atomic emission spectroscopy(ICP-OES),the NH_(4)Zn PO_(4)powders can be classified as a slow-release fertilizer where less than 15%of the ions were released in 24 h.A simple precipitation method using water,PVP,PVA,sucrose,and CTAB as a template can be used to synthesize NH4 Zn PO4 powders.In addition,this method may be extended for the preparation of other oxide materials.

Biomolecular changes and DNA targeting effect of sesamol in human lung adenocarcinoma (SK-LU-1) cells by FTIR microscopy

Objective: To investigate biomolecular alteration of sesamol on human lung adenocarcinoma(SK-LU-1) cells compared with cisplatin using Fourier transform infrared microscopy(FTIR). Methods: Cytotoxicity of sesamol was investigated against SK-LU-1 cells by using neutral red. DNA fragmentation and the cell cycle analysis were determined by agarose gel electrophoresis and flow cytometry, respectively. The FTIR microscopy technique was applied to explore the changes in cellular biochemical compositions in cells treated with sesamol that the biochemical and biological assays cannot cover. The alkylating property was determined by 4-(4-nitrobenzyl)pyridine assay. Results: Sesamol and cisplatin exerted an antiproliferative effect at 48 h with respective IC50 values of 2.7 and 0.07 m M. Both induced apoptosis by causing DNA damage and accumulation of cell populations at sub-G1. FTIR microscopy and Principle Component Analysis clearly discriminated the sesamol-and cisplatin-treated cells from the untreated cells or control. A significant increase of total lipid content was found in cisplatin-treated cells. Conformational changes in the proteins secondary structure from the β-helix to the β-sheet were found in both sesamol-and cisplatin-treated cells, as well as significant reductions in relative DNA content of both compared to the control were observed, suggesting DNA damage. A shift in the peak position of DNA region provides insight on the DNA interactions. Conclusions: The non-alkylating effect of sesamol based on the nitrobenzyl pyridine assay delineates the non-covalent binding mode of sesamol on DNA. Hydrogen bonding is the binding mode of sesamol on DNA, while for cisplatin it was covalent and hydrogen bonding.

Hydrogenated Amorphous Carbon Films from Palmyra Sugar

A simple,highly reproducible,and environmentally friendly method is a considered approach in generating renewable energy materials.Here,hydrogenated amorphous carbon(a-C)films have been successfully prepared from palmyra liquid sugar,employing spin-coating and spraying methods.Compared with the former method,the latter shows a significance in producing a better homogeneity in particle size and film thickness.The obtained films have a thickness of approximately 1000 to 100 nm and contain an sp^(2) hexagonal structure(~70%)and sp^(3) tetrahedral configuration(~30%)of carbons.The introduction of boron(B)and nitrogen(N)as dopants has created the local structural modification of bonding,inducing a slight change of electrical conductivity,electronic energy bandgap,and optical transparency near-infrared region.The obtained α-C film features a“green”semiconducting material.

Unleashing the potential of morphotropic phase boundary based hybrid triboelectric–piezoelectric nanogenerator

Morphotropic phase boundary(MPB)-based ceramics are excellent for energy harvesting due to their enhanced physical properties at phase boundaries,broad operating temperature range,and ability to customize properties for efficient conversion of mechanical energy into electrical energy.In this work,Bi_(1–x)Na_(x)Fe_(1–x)Nb_(x)O_(3)(x=0.20,0.30,0.32 and 0.40,BNFNO abbreviation)based ceramics were synthesized using a solid-state route and blended with Polydimethylsiloxane(PDMS)to achieve flexible composites.Various material characterization and energy harvesting were performed by designing a hybrid piezoelectric(PENG)-triboelectric(TENG)device.The voltage and current of PENG,TENG,and hybrid bearing same device area(2 cm×2 cm)were recorded as 11 V/0.3μA;60 V/0.7μA;110 V/2.2μA.The strategies for enhancing the output performance of the hybrid device were evaluated,such as increased surface area(creating micro-roughness and porous morphology)and increasing electrode size and multi-layer hybrid device formation.The self-powered acceleration monitoring was demonstrated using the hybrid device.Further,the low-frequency-based wave energy is converted into electrical energy,confirming the usage of hybrid PENG-TENG devices as a base for battery-free sensors and blue energy harvesting.

The role ofγ-C_(2)H_(5)NO_(2) as a new transient liquid phase in cold sintering process of BaTiO_(3) composites

Dielectric materials,such as barium titanate(BT)-based materials,have excellent dielectric properties but require high temperatures(above 1300℃)for ceramic fabrication,leading to high costs and energy loss.The cold sintering process(CSP)offers a solution to these issues and is gaining worldwide attention as an innovative fabrication route.In this work,we proposed an alternative organic ferroelectric phase,gamma-glycine(γ-GC),which acts as a transient liquid phase to fabricate high-density composites with barium titanate(BT)at low temperatures through CSP.Our findings show that the density of 15γ-GC/85BT reached 96.7%±1.6%when it was sintered at 120℃for 6 h under 10 MPa uniaxial pressure.Scanning electron microscopy‒energy dispersive X-ray spectroscopy(SEM‒EDS)mappings of the composite suggested thatγ-GC completely underwent the precipitation-dissolution process and,therefore,filled between BT particles.Moreover,X-ray diffraction(XRD)and Fourier-transform infrared spectroscopy(FTIR)confirmed the preservation ofγ-GC without undesired phase transformation.In addition,the ferroelectric and dielectric properties ofγ-GC/BT composites have been reported.The high dielectric constant(ε_(r))was 3600,and the low dielectric loss(tanδ)was 1.20 at 200℃and 100 kHz for the 15γ-GC/85BT composite.The hysteresis loop showed a remanent polarization(P_(r))of 0.55µC·cm^(−2)and a coercive field(E_(c))of 7.25 kV·cm^(−1).Our findings reaffirmed that an organic ferroelectric material(γ-GC)can act as a transient liquid phase in a CSP that can successfully and sustainably fabricateγ-GC/BT composites at low temperatures while delivering outstandingly high performance.

Dynamic observation of in-plane h-BN/graphene heterostructures growth on Ni(lll)

The lateraI incorporation of graphene and hexagonal boron nitride(h-BN)onto a substrate surface creates irvplane h-BN/graphene heterostructures,which have promising applications in novel two-dimensional electronic and photoelectronic devices.The quality of h-BN/graphene domain boundaries depends on their orientation,which is crucial for device performances.Here,the heteroepitaxial growth of graphene along the edges of h-BN domains on Ni(111)surfaces as well as the growth dynamics of h-BN using chemical vapor deposit!on(CVD)are in situ investigated by surface imaging measurements.The nucieating seed effect of h-BN has been revealed,which con tributes to the single orie ntation of heterostructures with epitaxial stitch i ng.Further,the growth of h-BN prior to that of graphene is essential to obtain high-quality in-plane h-BN/graphene heterostructures on Ni(111).The“compact to fractal”shape transition of h-BN domains appears with the increasing surface concentration of the growth blocks,suggesting that the dynamic growth mechanism follows diffusion-limited aggregation(DLA)but not reaction・limited aggregation(RLA).Our results provide in sights into the syn thesis of well-defi ned h-BN/graphene heterostructures and deep un derstanding of the growth dynamics of h-BN on metal surfaces.

A novel low-cost and environment-friendly cathode with large channels and high structure stability for potassium-ion storage

Potassium-ion batteries (KIBs) are promising candidates for large-scale energy storage due to the abundance of potassium and its chemical similarity to lithium.Nevertheless,the performances of KIBs are still unsatisfactory for practical applications,mainly hindered by the lack of suitable cathode materials.Herein,combining the strong inductive effect of sulphate and the feasible preparation of Fe^(2+)-containing compounds in oxalate system,a compound with novel architecture,K_(4)Fe_(3)(C_(2)O_(4))_(3)(SO_(4))_(2),has been identified as a lowcost and environmentally friendly cathode for stable potassium-ion storage.Its unique crystal structure possesses an unprecedented two-dimensional framework of triple layers,with 3.379Åinterlayer distance and large intralayer rings in the size of 4.576×6.846Å.According to first-principles simulations,such a configuration is favorable for reversible K-ion migration with a very low volume change of 6.4%.Synchrotron X-ray absorption spectra and X-ray diffraction characterizations at different charging/discharging states and electrochemical performances based on its half and full cells further verify its excellent reversibility and structural stability.Although its performance needs to be improved via further composition tuning with multi-valent transition metals,doping,structural optimization,etc.,this study clearly presents a stable structural model for K-ion cathodes with merits of low cost and environmental friendliness.

Enhanced giant dielectric properties and improved nonlinear electrical response in acceptor-donor (Al^(3+), Ta^(5+))-substituted CaCu_(3)Ti_(4)0_(12) ceramics

The giant dielectric bchavior of CaCu_(3)Ti_(4)0_(12)(CCTO)has been widely investigated owing to its potential applications in electronics;however,the loss tangent(tan8)of this material is too large for many applications.A partial substitution of CCTO ceramics with either Al^(3+) or Ta^(5+)-ions generally results in poorer nonlinear properties and an associated increase in tan8(to~0.29-1.15).However,first-principles calculations showed that self-charge compensation occurs between these two dopant ions when co-doped into Tit sites,which can improve the electrical properties of the grain boundary(GB).Surprisingly,in this study,a greatly enhanced breakdown electric field(~200--6588 V/cm)and nonlinear coefficient(-4.8-15.2)with a significantly reduced tan8(~0.010--0.036)were obtained by simultaneous partial substitution of CCTO with acceptor-donor(Al^(3+),Ta^(5+))dopants to produce(Al^(3+),Ta^(5+))-CCTO ceramics.The reduced tan8 and improved nonlinear properties were attributed to the synergistic effects of the co-dopants in the doped CCTO structure.The signifcant reduction in the mean grain size of the(Al^(3+),Ta^(5+))-CCTO ceramics compared to pure CCTO was mainly because of the Ta^(5+)-ions.Accordingly,the increased GB density due to the reduced grain size and the larger Schottky barrier height(Ф_(b))at the GBs of the co-doped CCTO ceramics were the main reasons for the greatly increased GB resistance,improved nonlinear properties,and reduced tan8 values compared to pure and single-doped CCTO.In addition,high dielectric constant values(ε'≈(0.52-2.7)×10^(4))were obtained.A fine-grained microstructure with highly insulating GBs was obtained by Ta doping,while co-doping with Ta^(5+) and Al^(3+ )resulted in a high Ф_(b).The obtained results are expected to provide useful guidelines for developing new giant dielectric ceramics with excellent dielectric properties.

Effects of Heliotropium indicum L.on Uterine Involution and Its Underlying Mechanisms:An in vivo and in vitro Study

Objective:To investigate the effect of Heliotropium indicum L.(H.indicum L.)on uterine involution and its underlying mechanisms in both in vivo and in vitro study.Methods:For in vivo studies,postpartum rats were randomly divided into 2 groups(n=24 for each):control group and treated group which were orally and daily administered with ethanolic extract of H.indicum L.(250 mg/kg body weight)until day 5 of postpartum.Uteri were collected for analysis of weight,cross-sectional area,collagen cross-sectional area,and collagen content on postpartum day 1,3,and 5(n=8 for each)from both groups.Blood samples were collected for hepatotoxicity and 17?-estradiol(E_(2))measurement.For in vitro studies,the extract effects on uterine contraction at half maximum effective concentration of 2.50 mg/mL were studied in organ bath system for at least 20 min.Results:Uterine parameters were significantly decreased after treated with extract of H.indicum L.(P<0.05).H.indicum L.extract significantly accelerated the reduction of those parameters and significantly decreased E_(2)(P<0.05).The extract facilitated uterine involution with no hepatotoxicity.H.indicum L.extract significantly stimulated uterine contraction(P<0.05)and synergized with oxytocin,prostaglandin and its precursor,linoleic acid.By investigating the different sequencing of the extract with the additional stimulants(added before or after),the two showed antagonistic effects,but still showed potentiated force when compared with control(without the stimulants).Conclusions:The underlying mechanisms by which H.indicum L.facilitated uterine involution might be due to reducing E_(2)which induces collagenase activity,leading to decreases in uterine weight and size and stimulating uterine contraction.Our study provides new findings for future drug development for facilitating uterine involution with H.indicum L.

Ultraelow loss tangent and giant dielectric permittivity with excellent temperature stability of TiO_(2) co-doped with isovalent-Zr4þ/ pentavalent-Ta5þ ions

The excellent giant dielectric properties(ExGDPs)are represented in the isovalenteZr4þ/pentavalent eTa5þions coedoped TiO_(2) with different coedoping percentages(x%ZrTTO).The dopants were dispersed homogeneously in a highly compactegrained ZrTTO microstructure.The mean grain size and cell parameters with bond lengths slightly enlarged as x%increased.The(1%e5%)ZrTTO oxides exhibited ultra elow tand values of 0.004e0.016 with the giant dielectric permittivity(ε0~2.7e3.7104);while theε0 of the 5%ZrTTO was slightly dependent on the temperature ranging from--60 to 200C,following the temperature dependence requirement for application in the X7/8/9R capacitors.Impedance spectroscopy showed a very large resistance of the grain boundaries.The dielectric properties of the 1%ZrTTO were strongly dependent on the applied DC electric field,indicating the dominant internal barrier layer capacitor(IBLC)effect.However,the dielectric properties of the 5%ZrTTO were nearly independent on the applied DC electric field up to 30 V/mm,which was primarily resulted from electron localization in defect dipoles.Therefore,the ExGDPs of the x%ZrTTO were attributed to the combined effects of the IBLC and localizedeelectron defectedipoles related to oxygen vacancies(Ti4þ,e--VO--e--,Ti4þand 3Ti4þ,e----VO--TaTi)and Ti4þ,e--TaTi.

Copper Nitroprusside-Based Electrochemical Sensor for Detection of Tryptophan

This work presents a novel electrochemical approach for detecting tryptophan through its interaction with copper nitroprusside,which is synthesized using a simple chemical co-precipitation method.The utilization of the reduction reaction inherent to copper nitroprusside effectively exhibits high selectivity against common interferences present in urine,such as melatonin,lactate,cytosine,cytidine,urea,ascorbic acid,creatine,creatinine,tyrosine,glycine,alanine,arginine,and lysine.The method demonstrates two linear ranges:0.0-0.15 mmol/L and 0.15-2.0 mmol/L with the sensitivities of 119.7±0.2μA/(mmol/L)and 9.9±0.4μA/(mmol/L),respectively.The limit of detection(3S_(B)/m)was determined to be 5.5μmol/L.Application of the sensor in synthetic urine yielded the recovery of 103%±5%.

Enhancement of output power density in a modified polytetrafluoroethylene surface using a sequential O_(2)/Ar plasma etching for triboelectric nanogenerator applications

In this work,the surface modification using a two-steps plasma etching has been developed for enhancing energy conversion performance in polytetrafluoroethylene(PTFE)triboelectric nanogenerator(TENG).Enhancing surface area by a powerful O_(2) and Ar bipolar pulse plasma etching without the use of CF_(4) gas has been demonstrated for the first time.TENG with modified surface PTFE using a sequential two-step O_(2)/Ar plasma has a superior power density of 9.9 W·m^(-2),which is almost thirty times higher than that of a pristine PTFE TENG.The synergistic combination of high surface area and charge trapping sites due to chemical bond defects achieved from the use of a sequential O_(2)/Ar plasma gives rise to the intensified triboelectric charge density and the enhancement of power output of PTFE-based TENG.The effects of plasma species and plasma etching sequence on surface morphologies and surface chemical species were investigated by a field emission scanning electron microscopy(FESEM),atomic force microscopy(AFM),and X-ray photoelectron spectroscopy(XPS).The correlation of surface morphology,chemical structure,and TENG performance was elucidated.In addition,the applications of mechanical energy harvesting for lighting,charging capacitors,keyboard sensing and operating a portable calculator were demonstrated.

Growth,coalescence,and etching of two-dimensional overlayers on metals modulated by near-surface Ar nanobubbles

The synthesis of high-quality ultrathin overlayers is critically dependent on the surface structure of substrates,especially involving the overlayer–substrate interaction.By using in situ surface measurements,we demonstrate that the overlayer–substrate interaction can be tuned by doping near-surface Ar nanobubbles.The interfacial coupling strength significantly decreases with near-surface Ar nanobubbles,accompanying by an“anisotropic to isotropic”growth transformation.On the substrate containing near-surface Ar,the growth front crosses entire surface atomic steps in both uphill and downhill directions with no difference,and thus,the morphology of the two-dimensional(2D)overlayer exhibits a round-shape.Especially,the round-shaped 2D overlayers coalesce seamlessly with a growth acceleration in the approaching direction,which is barely observed in the synthesis of 2D materials.This can be attributed to the immigration lifetime and diffusion rate of growth species,which depends on the overlayer–substrate interaction and the surface catalysis.Furthermore,the“round to hexagon”morphological transition is achieved by etching-regrowth,revealing the inherent growth kinetics under quasi-freestanding conditions.These findings provide a novel promising way to modulate the growth,coalescence,and etching dynamics of 2D materials on solid surfaces by adjusting the strength of overlayer–substrate interaction,which contributes to optimization of large-scale production of 2D material crystals.