Table of contents

Photodetectors (PDs) are the core component of multiple commercial optical sensing systems. Currently, the detection of ultra-weak ultraviolet (UV) optical signals is becoming increasingly important for wide range of applications in civil and military industries. Due to its wide band gap, low cost, and long-term stability, titanium dioxide (TiO₂) is an attractive material for UV photodetection. A kind of low-cost TiO₂ nanomaterial (named as P25) manufactured by flame hydrolysis is an easily available commercial material. However, a low-cost and high-sensitivity UV PD based on P25 has not been achieved until now. Here, a hybrid UV PD with monolayer CVD graphene covered by a thin film of P25 quantum dots was prepared for the first time, and its responsivity was approximately 10⁵ A W⁻¹ at 365 nm wavelength. The response time and recovery time of the UV PD were 32.6 s and 34 s, respectively. Strong light absorption and photocontrolled oxygen adsorption of the P25 layer resulted in high UV sensitivity. The UV PDs proposed in this work have great potential for commercialization due to their low cost and high sensitivity.

Upconversion (UC) of lanthanide-doped nanostructure has the unique ability to convert low energy infrared (IR) light to high energy photons, which has significant potential for energy conversion applications. This review concisely discusses the basic concepts and fundamental theories of lanthanide nanostructures, synthesis techniques, and enhancement methods of upconversion for photovoltaic and for near-infrared (NIR) photodetector (PD) application. In addition, a few examples of lanthanide-doped nanostructures with improved performance were discussed, with particular emphasis on upconversion emission enhancement using coupling plasmon. The use of UC materials has been shown to significantly improve the NIR light-harvesting properties of photovoltaic devices and photocatalytic materials. However, the inefficiency of UC emission also prompted the need for additional modification of the optical properties of UC material. This improvement entailed the proper selection of the host matrix and optimization of the sensitizer and activator concentrations, followed by subjecting the UC material to surface-passivation, plasmonic enhancement, or doping. As expected, improving the optical properties of UC materials can lead to enhanced efficiency of PDs and photovoltaic devices.

In Part I of this topical review, we discussed dynamical phenomena in nanomagnets, focusing primarily on magnetization reversal with an eye to digital applications. In this part, we address mostly wave-like phenomena in nanomagnets, with emphasis on spin waves in myriad nanomagnetic systems and methods of controlling magnetization dynamics in nanomagnet arrays which may have analog applications. We conclude with a discussion of some interesting spintronic phenomena that undergird the rich physics exhibited by nanomagnet assemblies.

2D van der Waals materials are crystals composed of atomic layers, which have atomic thickness scale layers and rich distinct properties, including ultrafast optical response, surface effects, light-mater interaction, small size effects, quantum effects and macro quantum tunnel effects. With the exploration of saturable absorption characteristic of 2D van der Waals materials, a series of potential applications of 2D van der Waals materials as high threshold, broadband and fast response saturable absorbers (SAs) in ultrafast photonics have been proposed and confirmed. Herein, the photoelectric characteristics, nonlinear characteristic measurement technique of 2D van der Waals materials and the preparation technology of SAs are systematically described. Furthermore, the ultrafast pulsed fiber lasers based on classical 2D van der Waals materials including graphene, transition metal chalcogenides, topological insulators and black phosphorus have been fully summarized and analyzed. On this basis, opportunities and directions in this field, as well as the research results of ultrafast pulsed fiber lasers based on the latest 2D van der Waals materials (such as PbO, FePSe₃, graphdiyne, bismuthene, Ag₂S and MXene etc), are reviewed and summarized.

Many technical-grade reagents, including oleylamine, are broadly used as ligands in nanocrystal synthesis, allowing for cost-effective, and more environmentally friendly, preparation of materials in useful quantities. Impurities can represent 30% or more of these reagent blends, and have frequently emerged as substantial drivers of nanocrystal morphology, assembly, or other physical properties, making it important to understand their composition. Some functional alkyl reagents are derived from natural sources (e.g. often beef tallow, in the case of oleylamine), introducing alkyl chain structures very different than those that might be expected as side products of synthesis from pure feedstocks. Additionally, impurities can exhibit variations based on biological factors (e.g. species, diet, season). In biology, blends of alkyl chains allow for surprisingly sophisticated function of amphiphiles in the cell membrane, pointing to the possibility of similar control in synthetic materials if reagent composition were either better controlled or better understood. Here, we provide brief context on the breadth of roles technical-grade impurities have played in nanocrystal materials, followed by a perspective on oleylamine impurities, their physical properties, and their potential contributions to nanomaterial function.

MXenes are a group of inorganic two-dimensional (2D) nanomaterial, and have raised significant interests in biomedical areas. Ti₃C₂T_x, as an important member of MXene family, is widely studied because of its biodegradability and low-cytotoxicity. However, their single antibacterial mechanism and poor stability in aqueous solution need to be improved, especially for the antimicrobial applications. In this work, a MXene-based hybrid antibacterial system (M-HAS) was developed and its synergistic antibacterial activity was investigated. In the M-HAS, 2D few-layer Ti₃C₂T_x (FL-Ti₃C₂T_x) was modified with hydrophilic polymers and thereby used as carriers for silver nanoparticles (Ag NPs). By assembling these two substrates, photodynamic performance of the prepared system is significantly improved with a large amount of reactive oxygen species produced under 660 nm laser. Antibacterial effects of the M-HAS are enhanced by over 4 times with irradiation. In another word, the developed hybrid system displays excellent photodynamic antibacterial synergistic properties. This work takes advantage of the photodynamic properties of each component in the M-HAS to achieve efficient antibacterial activity and proposes an innovative approach to develop the 2D FL-Ti₃C₂T_x-based antibacterial platform.

Electrospun polyvinyl alcohol (PVA) and tragacanth gum (TG) were used to develop nanofibrous scaffolds containing poorly water-soluble β-Sitosterol (β-S). Different concentrations and ratios of the polymeric composite including β-S (10% w v⁻¹) in PVA (8% w v⁻¹) combined with TG (0.5 and 1% w v⁻¹) were prepared and electrospun. The synthesis method includes four electrospinning parameters of solution concentration, feeding rate, voltage, and distance of the collector to the tip of the needle, which are independently optimized to achieve uniform nanofibers with a desirable mean diameter for cell culture. The collected nanofibers were characterized by SEM, FTIR, and XRD measurements. A contact angle measurement described the hydrophilicity of the scaffold. MTT test was carried out on the obtained nanofibers containing L929 normal fibroblast cells. The mechanical strength, porosity, and deterioration of the scaffolds were well discussed. The mean nanofiber diameters ranged from 63 ± 20 nm to 97 ± 46 nm. The nanofibers loaded with β-S were freely soluble in water and displayed a remarkable biocompatible nature. The cultured cells illustrated sheet-like stretched growth morphology and penetrated the nanofibrous pores of the PVA/β-S/TG scaffolds. The dissolution was related to submicron-level recrystallization of β-S with sufficient conditions for culturing L929 cells. It was concluded that electrospinning is a promising technique for poorly water-soluble β-S formulations that could be used in biomedical applications.

Bcl-2, an anti-apoptotic protein, is always overexpressed in tumor cells to suppress the pro-apoptotic function of Bax, thereby prolonging the life of the tumor. However, BH3 proteins could directly activate Bax via antagonizing Bcl-2 to induce apoptosis in response to the stimulation. Thus, mimicking BH3 proteins with a peptide is a potential strategy for anti-cancer therapy. Unfortunately, clinical translation of BH3-mimic peptide is hindered by its inefficacious cellular internalization and proteolysis resistance. Herein, we translated a BH3-mimic peptide into a peptide-auric spheroidal nanocluster (BH3-AuNp), in which polymeric BH3-Auric precursors [Au¹⁺-S-BH3]_n are in situ self-assembled on the surface of gold nanoparticles by a one-pot synthesis. Expectedly, this strategy could improve the anti-proteolytic ability and cytomembrane penetrability of the BH3 peptide. As a result, BH3-AuNp successfully induced the apoptosis of two cancer cell lines by an order of magnitude compared to BH3. This therapeutic and feasible peptide nano-engineering strategy will help peptides overcome the pharmaceutical obstacles, awaken its biological functions, and possibly revive the research about peptide-derived nanomedicine.

In this work, a SiGeSn/GeSn/SiGeSn single quantum well was grown and characterized. The sample has a thicker GeSn well of 22nm compared to a previously reported 9nm well configuration. The thicker well leads to: (i) lowered ground energy level in Γ valley offering more bandgap directness; (ii) increased carrier density in the well; and (iii) improved carrier collection due to increased barrier height. As a result, significantly enhanced emission from the quantum well was observed. The strong photoluminescence (PL) signal allows for the estimation of quantum efficiency (QE), which was unattainable in previous studies. Using pumping-power-dependent PL spectra at 20K, the peak spontaneous QE and external QE were measured as 37.9% and 1.45%, respectively.

The multifunctional upconversion nanoparticles (UCNPs) are fascinating tool for biological applications. In the present work, photon upconverting NaGdF₄:Yb,Er and Ag nanoparticles decorated NaGdF₄:Yb,Er (NaGdF₄:Yb,Er@Ag) nanoparticles were prepared using a simple polyol process. Rietveld refinement was performed for detailed crystal structural and phase fraction analysis. The morphology of the NaGdF₄:Yb,Er@Ag was examined using high-resolution transmission electron microscope, which reveals silver nanoparticles of 8 nm in size were decorated over spherical shaped NaGdF₄:Yb,Er nanoparticles with a mean particle size of 90 nm. The chemical compositions were confirmed by EDAX and inductively coupled plasma-optical emission spectrometry analyses. The upconversion luminescence (UCL) of NaGdF₄:Yb,Er at 980 nm excitation showed an intense red emission. After incorporating the silver nanoparticles, the UCL intensity decreased due to weak scattering and surface plasmon resonance effect. The VSM magnetic measurement indicates both the UCNPs possess paramagnetic behaviour. The NaGdF₄:Yb,Er@Ag showed computed tomography imaging. Magnetic resonance imaging study exhibited better T1 weighted relaxivity in the NaGdF₄:Yb,Er than the commercial Gd-DOTA. For the first time, the optical trapping was successfully demonstrated for the upconversion NaGdF₄:Yb,Er nanoparticle at near-infrared 980 nm light using an optical tweezer setup. The optically trapped UCNP possessing paramagnetic property exhibited a good optical trapping stiffness. The UCL of trapped single UCNP is recorded to explore the effect of the silver nanoparticles. The multifunctional properties for the NaGdF₄:Yb,Er@Ag nanoparticle are demonstrated.

Till date, the existing understanding of negative differential resistance (NDR) is obtained from metal-ferro–metal–insulator–semiconductor (MFMIS) FET, and it has been utilized for both MFMIS and metal–ferro–insulator–semiconductor (MFIS) based NCFETs. However, in MFIS architecture, the ferroelectric capacitance (C_FE) is not a lumped capacitance. Therefore, for MFIS negative capacitance (NC) devices, the physical explanation which governs the NDR mechanism needs to be addressed. In this work, for the first time, we present the first principle explanation of the NDR effect in MFIS NC FDSOI. We found that the output current variation with the drain to source voltage (V_DS), (i.e. g_ds) primarily depends upon two parameters: (a) V_DS dependent inversion charge gradient (∂n/∂V_DS); (b) V_DS sensitive electron velocity (∂v/∂V_DS), and the combined effect of these two dependencies results in NDR. Further, to mitigate the NDR effect, we proposed the BOX engineered NC FDSOI FET, in which the buried oxide (BOX) layer is subdivided into the ferroelectric (FE) layer and the SiO₂ layer. In doing so, the inversion charge in the channel is enhanced by the BOX engineered FE layer, which in turn mitigates the NDR and a nearly zero g_ds with a minimal positive slope has been obtained. Through well-calibrated TCAD simulations, by utilizing the obtained positive g_ds, we also designed a V_DS independent constant current mirror which is an essential part of analog circuits. Furthermore, we discussed the impact of the FE parameter (remanent polarization and coercive field) variation on the device performances. We have also compared the acquired results with existing literature on NC-based devices, which justifies that our proposed structure exhibits complete diminution of NDR, thus enabling its use in analog circuit design.

A new class of transparent graphene electrode based organic–inorganic halide perovskite photodetectors with broad spectral response is developed. These ultrasensitive devices exhibit high ON/OFF current ratio, high linear dynamic range, broad spectral range, excellent detection for weak light and easy fabrication with low-cost. Their semi-transparent feature and distinct photodetecting function for both sides would provide new applications affecting our daily lives.

In this work, two silicon nanostructures were doped into polymer/nematic liquid crystal composites to regulate the electric-optical performance. Commercial SiO₂ nanoparticles and synthesized thiol polyhedral oligomeric silsesquioxane (POSS-SH) were chosen as the dopants to afford the silicon nanostructures. SiO₂ nanoparticles were physically dispersed in the composites and the nanostructure from POSS-SH was implanted into the polymer matrix of the composites via photoinduced thiol-ene crosslinking. Scanning electron microscopy results indicated that the implantation of POSS microstructure into the polymer matrix was conducive to obtaining the uniform porous polymer microstructures in the composites while the introduction of SiO₂ nanoparticles led to the loose and heterogeneous polymer morphologies. The electric-optical performance test results also demonstrated that the electric-optical performance regulation effect of POSS microstructure was more obvious than that of SiO₂ nanoparticles. The driving voltage was reduced by almost 80% if the concentration of POSS-SH in the composite was nearly 8 wt% and the sample could be completely driven by the electric field whose voltage was lower than the safe voltage for continuous contact (24 V). This work could provide a creative approach for the regulation of electric-optical performance for polymer/nematic liquid crystal composites and the fabrication of low voltage-driven PDLC films for smart windows.

The formation of an interfacial layer is believed to affect the ferroelectric properties in HfO₂ based ferroelectric devices. The atomic layer deposited devices continue suffering from a poor bottom interfacial condition, since the formation of bottom interface is severely affected by atomic layer deposition and annealing process. Herein, the formation of bottom interfacial layer was controlled through deposition of different bottom electrodes (BE) in device structure W/HZO/BE. The transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy analyses done on devices W/HZO/W and W/HZO/IrO_x suggest the strong effect of IrO_x in controlling bottom interfacial layer formation while W/HZO/W badly suffers from interfacial layer formation. W/HZO/IrO_x devices show high remnant polarization (2P_r) ∼ 53 μC cm⁻², wake-up free endurance cycling characteristics, low leakage current with demonstration of low annealing temperature requirement as low as 350 °C, valuable for back-end-of-line integration. Further, sub-5 nm HZO thicknesses-based W/HZO/IrO_x devices demonstrate high 2P_r and wake-up free ferroelectric characteristics, which can be promising for low power and high-density memory applications. 2.2 nm, 3 nm, and 4 nm HZO based W/HZO/IrO_x devices show 2P_r values 13.54, 22.4, 38.23 μC cm⁻² at 4 MV cm⁻¹ and 19.96, 30.17, 48.34 μC cm⁻² at 5 MV cm⁻¹, respectively, with demonstration of wake-up free ferroelectric characteristics.

The development of powerful terahertz (THz) emitters is the cornerstone for future THz applications, such as communication, medical biology, non-destructive inspection, and scientific research. Here, we report the THz emission properties and mechanisms of mushroom-shaped InAs nanowire (NW) network using linearly polarized laser excitation. By investigating the dependence of THz signal to the incidence pump light properties (e.g. incident angle, direction, fluence, and polarization angle), we conclude that the THz wave emission from the InAs NW network is induced by the combination of linear and nonlinear optical effects. The former is a transient photocurrent accelerated by the photo-Dember field, while the latter is related to the resonant optical rectification effect. Moreover, the p-polarized THz wave emission component is governed by the linear optical effect with a proportion of ∼85% and the nonlinear optical effect of ∼15%. In comparison, the s-polarized THz wave emission component is mainly decided by the nonlinear optical effect. The THz emission is speculated to be enhanced by the localized surface plasmon resonance absorption of the In droplets on top of the NWs. This work verifies the nonlinear optical mechanism in the THz generation of semiconductor NWs and provides an enlightening reference for the structural design of powerful and flexible THz surface and interface emitters in transmission geometry.

We present a 'top-down' patterning technique based on ion milling performed at low-temperature, for the realization of oxide two-dimensional electron system devices with dimensions down to 160 nm. Using electrical transport and scanning Superconducting QUantum Interference Device measurements we demonstrate that the low-temperature ion milling process does not damage the 2DES properties nor creates oxygen vacancies-related conducting paths in the STO substrate. As opposed to other procedures used to realize oxide 2DES devices, the one we propose gives lateral access to the 2DES along the in-plane directions, finally opening the way to coupling with other materials, including superconductors.

Controllable tailoring and understanding the phase-structure relationship of the 1T phase two-dimensional (2D) materials are critical for their applications in nanodevices. The in situ transmission electron microscope (TEM) could regulate and monitor the evolution process of the nanostructure of 2D material with atomic resolution. In this work, a controllably tailoring 1T-CrTe₂ nanopore is carried out by the in situ TEM. A preferred formation of the 1T-CrTe₂ border structure and nanopore healing process are studied at the atomic scale. The controllable tailoring of the 1T phase nanopore could be achieved by regulating the transformation of two types of low indices of crystal faces {$10\bar{1}0$} and {$11\bar{2}0$} at the nanopore border. Machine learning is applied to automatically process the TEM images with high efficiency. By adopting the deep-learning-based image segmentation method and augmenting the TEM images specifically, the nanopore of the TEM image could be automatically identified and the evaluation result of DICE metric reaches 93.17% on test set. This work presents the unique structure evolution of 1T phase 2D material and the computer aided high efficiency TEM data analysis based on deep learning. The techniques applied in this work could be generalized to other materials for controlled nanostructure regulation and automatic TEM image analyzation.

Photochemical conversion of CO₂ into solar fuels is one of the promising strategies to reducing the CO₂ emission and developing a sustainable carbon economy. For the more efficient utilization of solar spectrum, several approaches were adopted to pursue the visible-light-driven SrTiO₃. Herein, oxygen vacancy was introduced over the commercial SrTiO₃ (SrTiO_3−x) via the NaBH₄ thermal treatment, to extend the light absorption and promote the CO₂ adsorption over SrTiO₃. Due to the mid-gap states resulted from the oxygen deficiency, combined with the intrinsic energy level of SrTiO₃, the SrTiO_3−x catalyst exhibited excellent CO productivity (4.1 μmolˑg⁻¹ˑh⁻¹) and stability from the CO₂ photodissociation under the visible-light irradiation (λ > 400 nm). Then, surface alkalization over SrTiO_3−x (OH-SrTiO_3−x) was carried out to further enhance the CO₂ adsorption/activation over the surface base sites and provide the OH ions as hole acceptor, the surface alkali OH connected with Sr site of SrTiO₃ could also weaken the Sr–O bonding thus facilitate the regeneration of surface oxygen vacancy under the light illumination, thus resulting in 1.5 times higher CO productivity additionally. This study demonstrates that the synergetic modulation of alkali OH and oxygen vacancy over SrTiO₃ could largely promote the CO₂ photodissociation activity.

Transition metal oxides are generally designed as hybrid nanostructures with high performance for supercapacitors by enjoying the advantages of various electroactive materials. In this paper, a convenient and efficient route had been proposed to prepare hierarchical coral-like MnCo₂O_4.5@Co–Ni LDH composites on Ni foam, in which MnCo₂O_4.5 nanowires were enlaced with ultrathin Co–Ni layered double hydroxides nanosheets to achieve high capacity electrodes for supercapacitors. Due to the synergistic effect of shell Co–Ni LDH and core MnCo₂O_4.5, the outstanding electrochemical performance in three-electrode configuration was triggered (high area capacitance of 5.08 F cm⁻² at 3 mA cm⁻² and excellent rate capability of maintaining 61.69% at 20 mA cm⁻²), which is superior to those of MnCo₂O_4.5, Co–Ni LDH and other metal oxides based composites reported. Meanwhile, the as-prepared hierarchical MnCo₂O_4.5@Co–Ni LDH electrode delivered improved electrical conductivity than that of pristine MnCo₂O_4.5. Furthermore, the as-constructed asymmetric supercapacitor using MnCo₂O_4.5@Co–Ni LDH as positive and activated carbon as negative electrode presented a rather high energy density of 220 μWh cm⁻² at 2400 μW cm⁻² and extraordinary cycling durability with the 100.0% capacitance retention over 8000 cycles at 20 mA cm⁻², demonstrating the best electrochemical performance compared to other asymmetric supercapacitors using metal oxides based composites as positive electrode material. It can be expected that the obtained MnCo₂O_4.5@Co–Ni LDH could be used as the high performance and cost-effective electrode in supercapacitors.

The supercapacitors possessing high energy storage and long serving period have strategic significance to solve the energy crisis issues. Herein, fluffy nano-dendrite structured cobalt phosphide (CoP) is grown on carbon cloth through simple hydrothermal and electrodeposition treatments (CoP/C-HE). Benefit from its excellent electrical conductivity and special structure, CoP/C-HE manifests a high specific capacity of 461.4 C g⁻¹ at 1 A g⁻¹. Meanwhile, the capacity retention remains 92.8% over 10 000 cycles at 5 A g⁻¹, proving the superior cycling stability. The phase conversion of Co₂P during the activation process also contributes to the improved performance. The assembled two-electrode asymmetric supercapacitor demonstrates excellent performance in terms of energy density (42.4 W h kg⁻¹ at a power density of 800.0 W kg⁻¹) and cycling stability (86.3% retention over 5000 cycles at 5 A g⁻¹), which is superior to many reported cobalt-based supercapacitors. Our work promotes the potential of transition metal phosphides for the applications in supercapacitors.

Taking advantage of both Faradaic and carbonaceous materials is an efficient way to synthesize composite electrodes with enhanced performance for supercapacitors. In this study, NiCo₂S₄ nanoflakes were grown on the surface of nitrogen-doped hollow carbon nanospheres (NHCSs), forming a NiCo₂S₄/NHCS composite with a core–shell structure. This three-dimensionally confined growth of NiCo₂S₄ can effectively inhibit its aggregation and facilitate mass transport and charge transfer. Accordingly, the NiCo₂S₄/NHCS composite exhibited high cycling stability with only 9.2% capacitance fading after 10 000 cycles, outstanding specific capacitance of 902 F g⁻¹ at 1 A g⁻¹, and it retained 90.6% of the capacitance at 20 A g⁻¹. Moreover, an asymmetric supercapacitor composed of NiCo₂S₄/NHCS and activated carbon electrodes delivered remarkable energy density (31.25 Wh kg⁻¹ at 750 W kg⁻¹), excellent power density (15003 W kg⁻¹ at 21.88 Wh kg⁻¹), and satisfactory cycling stability (13.4% capacitance fading after 5000 cycles). The outstanding overall performance is attributed to the synergistic effect of the NiCo₂S₄ shell and NHSC core, which endows the composite with a stable structure, high electrical conductivity, abundant active reaction sites, and short ion-transport pathways. The synthesized NiCo₂S₄/NHCS composite is a competitive candidate for the electrodes of high-performance supercapacitors.

Fabrication of transition metal dichalcogenide quantum dots (QDs) is complex and requires submerging powders in binary solvents and constant tuning of wavelength and pulsed frequency of light to achieve a desired reaction. Instead of liquid state photoexfoliation, we utilize infrared laser irradiation of free-standing MoS₂ flakes in transmission electron microscope (TEM) to achieve solid-state multi-level photoexfoliation of QDs. By investigating the steps involved in photochemical reaction between the surface of MoS₂ and the laser beam, we gain insight into each step of the photoexfoliation mechanism and observe high yield production of QDs, led by an inhomogeneous crystalline size distribution. Additionally, by using a laser with a lower energy than the indirect optical transition of bulk MoS₂, we conclude that the underlying phenomena behind the photoexfoliation is from multi-photon absorption achieved at high optical outputs from the laser source. These findings provide an environmentally friendly synthesis method to fabricate QDs for potential applications in biomedicine, optoelectronics, and fluorescence sensing.

The MnO/C composites were obtained by co-precipitation method, which used Mn₃O₄ nanomaterials as precursors and dopamine solution after ultrasonic mixing and calcination under N₂ atmosphere at different temperatures. By studying the difference of MnO/C nanomaterials formed at different temperatures, it was found that with the increase of calcination temperature, the materials appear obvious agglomeration. The optimal calcination temperature is 400 °C, and the resulting MnO/C is a uniformly dispersed slender nanowire structure. The specific capacitance of MnO/C nanowires can reach 356 F g⁻¹ at 1 A g⁻¹. In the meantime, the initial capacitance of MnO/C nanowires remains 106% after 5000 cycles. Moreover, the asymmetric supercapacitor was installed, which displays a tremendous energy density of 30.944 Wh kg⁻¹ along with a high power density of 10 kW kg⁻¹. The composite material reveals a promising prospect in the application of supercapacitors.

The development of new electromagnetic interference materials has attracted much attention in the information warfare. Herein, a novel KPA@${\text{Fe}}_{3}{O}_{4}$ composite particle was synthesized via a microcrystalline co-precipitation method. X-ray diffractions, scanning electron microscopes and vibrating sample magnetometer measurements were used to characterize the products. The results indicated that the surface of the potassium picrate (KPA) crystals was covered by magnetic ${\text{Fe}}_{3}{O}_{4}$ nanoparticles, and composite particles exhibited excellent magnetic properties. Furthermore, the thermal behavior of the composite particles was investigated by differential scanning calorimetry, which showed that the composite particles inherited the energetic property of pure KPA crystals when the mass fraction of magnetic component was 50%, or 65%. As for the composite particles with 75% magnetic component, the thermal stability of was poor. In addition, the magnetic directional aggregation performance of composite particles was analyzed by dynamic simulation, which moved toward the magnetic source. For the composite particles with 50% magnetic component, the maximum concentration was about 63 times of the initial concentration, and the peak velocity was 0.63 m s⁻¹. With the mass fraction of magnetic component increasing to 65%, the concentration and velocity of the composite particles generally increased at the corresponding moment. As the mass fraction of magnetic component increased to 75%, the change of them was not obvious. Therefore, the composite particles with ${\text{Fe}}_{3}{O}_{4}$/KPA mass ratios of 65/35 had the best comprehensive properties. The excellent energetic and magnetic directional aggregation properties can allow the composites to be used in many potential applications in the information warfare.

A novel method for the detection of procalcitonin in a homogeneous system by matched carbon dots (CDs) labeled immunoprobes was proposed based on the principle of FRET and double antibody sandwich method. Blue-emitting carbon dots with a strong fluorescence emission range of 400–550 nm and red-emitting carbon dots with the best excitation range of 410–550 nm were prepared before they reacted with procalcitonin protoclone antibody pairs to form immunoprobes. According to the principles of FRET, blue-emitting carbon dots were selected as the energy donor and red-emitting carbon dots as the energy receptor. The external light source excitation (310 nm) could only cause weak luminescence of CDs. However, once procalcitonin was added, procalcitonin and antibodies would be combined with each other quickly (≤20 min). Here, blue-emitting carbon dots acquired energy could be transferred to red-emitting carbon dots efficiently, causing the emitted fluorescence enhancement of red-emitting carbon dots. The fluorescence detection results in PBS buffer solution and diluted rabbit blood serum showed that the fluorescence intensity variation was linear with the concentration of procalcitonin. There was a good linear relationship between F/F0 and procalcitonin concentrations in PBS buffer solution that ranged from 0 to 100 ng ml⁻¹, and the linear equation was F/F0 = 0.004 * C_pct + 0.98359. Detection in the diluted rabbit serum led to the results that were linear in two concentration ranges, including 0–40 ng ml⁻¹ and 40–100 ng ml⁻¹, and the detection limit based on 3σ K⁻¹ was 0.52 ng ml⁻¹. It is likely that this matched CDs labeled immunoprobes system can provide a new mode for rapid homogeneous detection of disease markers.

Charge transport physics in InAs/GaSb bi-layer systems has recently attracted attention for the experimental search for two-dimensional topological superconducting states in solids. Here we report measurement of charge transport spectra of nano devices consisting of an InAs/GaSb quantum well sandwiched by tantalum superconductors. We explore the current-voltage relation as a function of the charge-carrier density in the quantum well controlled by a gate voltage and an external magnetic field. We observe three types of differential resistance peaks, all of which can be effectively tuned by the external magnetic field, and, however, two of which appear at electric currents independent of the gate voltage, indicating a dominant mechanism from the superconductor and the system geometry. By analyzing the spectroscopic features, we find that the three types of peaks identify Andreev reflections, quasi-particle interference, and superconducting transitions in the device, respectively. Our results provide a basis for further exploration of possible topological superconducting state in the InAs/GaSb system.

Lithium–sulfur (Li–S) batteries have been considered to be one of the most promising energy storage devices in the next generation. However, the insulating properties of sulfur and the shuttle effect of soluble lithium polysulfides (LiPSs) seriously hinder the practical application of Li–S batteries. In this paper, a novel porous organic polymer (HUT3) was prepared based on the polycondensation between melamine and 1,4-phenylene diisocyanate. The micro morphology of HUT3 was improved by in situ growth on different mass fractions of rGO (5%, 10%, 15%), and the obtained HUT3-rGO composites were employed as sulfur carriers in Li–S batteries with promoted the sulfur loading ratio and lithium-ion mobility. Attributed to the synergistic effect of the chemisorption of polar groups and the physical constraints of HUT3 structure, HUT3-rGO/S electrodes exhibits excellent capacity and cyclability performance. For instance, HUT3-10rGO/S electrode exhibits a high initial specific capacity of 950 mAh g⁻¹ at 0.2 C and retains a high capacity of 707 mAh g⁻¹ after 500 cycles at 1 C. This work emphasizes the importance of the rational design of the chemical structure and opens up a simple way for the development of cathode materials suitable for high-performance Li–S batteries.

Strain engineering can effectively modify the materials lattice parameters at atomic scale, hence it has become an efficient method for tuning the physical properties of two-dimensional (2D) materials. The study of the strain regulated interlayer coupling is deserved for different kinds of heterostructures. Here, we systematically studied the strain engineering of WSe₂/WS₂ heterostructures as well as their constituent monolayers. The measured Raman and photoluminescence spectra demonstrate that the strain can evidently modulate the phonon energy and exciton emission of monolayer WSe₂ and WS₂ as well as the WSe₂/WS₂ heterostructures. The tensile strain can tune the electronic band structure of WSe₂/WS₂ heterostructure, as well as enhance the interlayer coupling. It is further revealed that the photoluminescence intensity ratio of WS₂ to WSe₂ in our WSe₂/WS₂ heterobilayer increases monotonically with tensile strain. These findings can broaden the understanding and practical application of strain engineering in 2D materials with nanometer-scale resolution.

All-inorganic lead-halide perovskites have emerged as an exciting material owing to their excellent optoelectronic properties and high stability over hybrid organometallic perovskites. Nanowires of these materials, in particular, have shown great promise for optoelectronic applications due to their high optical absorption coefficient and low defect state density. However, the synthesis of the most promising alpha-Cesium lead iodide (α-CsPbI₃) nanowires is challenging as it is metastable and spontaneously converts to a non-perovskite δ-phase. The hot-injection method is one of the most facile, well-controlled, and commonly used approaches for synthesizing CsPbX₃ nanostructures. But the exact mechanism of growing these nanowires in this technique is not clear. Here, we show that the hot-injection method produces photoactive phases of quantum dots (QDs) and nanowires of CsPbBr_3, and QDs of CsPbI₃, but CsPbI₃ nanowires are grown in their non-perovskite δ-phase. Monitoring the nanowire growth during the hot-injection technique and through detailed characterization, we establish that CsPbI₃ nanowires are formed in the non-perovskite phase from the beginning rather than transforming after its growth from perovskite to a non-perovskite phase. We have discussed a possible mechanism of how non-perovskite nanowires of CsPbI₃ grow at the expense of photoactive perovskite QDs. Our findings will help to synthesize nanostructures of all-inorganic perovskites with desired phases, which is essential for successful technological applications.