Nano

Recent advances in miniaturized nano-based devices are rapidly extending the boundaries of biomedical technologies, particularly biosensors. Highly selective biosensors with the ability to simultaneously detect multiple targets were developed in recent years. The most eye-catching classifications of such biosensors coupled with the emergence of stimuli-responsive and CRISPR/Cas-sensitive systems. Furthermore, attractive features of wearable and implantable biosensors have led to the design of portable, remote controllable diagnostic systems for tackling healthcare challenges in every part of the world, especially in places with limited access to clinical resources. Nevertheless, there are still some barriers to widespread applications of biosensors due mainly to their high costs and the lack of a single biosensing device for highly selective targeting of multiple analytes. Herein, we review the latest developments in biomedical technologies with a focus on biosensors including smart stimuli-responsive, CRISPR/Cas-sensitive, wearable, and implantable biosensors to spark innovations in this field.

Polyimide (PI) is an important engineering material, but its poor thermal conductivity limits its application in the field of electronic packaging. In this work, we prepared boron nitride nanosheets (BNNSs) and boron nitride nanosheets/silver nanoparticles (BNNSs/AgNPs) hybrid fillers which combined successfully with the PI matrix by in-situ polymerization to produce high-thermal-conductivity PI composites. The results showed that when the filler addition was 20wt.%, the composites had the best overall performance, and the thermal conductivities of the BNNSs/PI and BNNSs/AgNPs/PI composite films were 0.863W$\cdot$m${}^{-1}\cdot {\mathrm{\text{K}}}^{-1}$ and 1.175W$\cdot$m${}^{-1}$$\cdot$K${}^{-1}$, respectively, which improved 506% and 726%, respectively, compared with pure PI. Furthermore, the volume resistivity of the composites is higher than 10${}^{17}\mathrm{\Omega }\cdot \mathrm{\text{cm}}$, indicating an excellent insulating property. At the same time, when used as the thermal interface material (TIM) for light-emitting diode (LED) chips, the composites have significantly improved heat dissipation effect and excellent mechanical properties at 75^∘C, which are expected to be widely used in the field of electronic packaging.

Solvent-free nanofluid displays liquid-like function in the absence of solvent at room temperature by grafting organic salts on the surface of materials. In this study, carbon nanotube (CNT) fluid is synthesized by a chemical grafting method for the preparation of CNTs/copper (Cu) composite powder. After hot-pressing and sintering, the CNTs-fluid/Cu composites are further treated by hot rolling to improve their mechanical properties. The microstructure and mechanical properties of the as-obtained composites are systematically characterized by SEM, TEM, FTIR, Raman, rheological analysis, hardness and tensile tests. It is demonstrated that the optimal mechanical properties of the composite can be achieved by adding 0.75wt.% CNTs nanofluid. The yield and tensile strength of the resultant material are about 397.6MPa and 517.5MPa, respectively, which are 282% and 156% higher than that of pure Cu. Meanwhile, its hardness value reaches 152.2HV, which is increased by 27% and 38% of pure Cu and the unrolled sample, respectively. Such significant property improvement is conjointly contributed by load transfer strengthening, Orowan strengthening, matrix strengthening and thermal mismatch. This study provides a new insight into the interface structure to enhance the mechanical properties of metal matrix composites.

Carbon nanotube (CNT) long array with higher aspect ratio is an ideal electrode material for high performance supercapacitors due to its excellent conductivity and high specific surface area (SSA). How to quickly and concisely prepare high-quality CNT long-arrays is the key to achieving large-scale application. Herein, high-quality spring-like CNT (tube diameter 5–8nm) long arrays (100–400$\mu$m) with high purity (96.2% after purification) and ultrahigh graphitization ($I_G∕I_D>3.0$) were fabricated in a high yield (eight times) by a self-supporting catalyst chemical vapor deposition (CVD) method, and its formation process was first investigated under specific conditions of iron content in catalyst, growth temperature and carbon source species. The SSAs can reach 728m²/g, which is more than twice that of MWCNTs on the market. The high graphitization and ultra-large SSAs of this spring-like CNT arrays as electrodes exhibit potential electrochemical performance.

Using the plasma-enhanced chemical vapor deposition method, we grow vertical graphene thin films onto SiO₂/Si substrates, which is a special format of graphene composed of numerous macroscopically uniformly distributed graphene flakes approximately vertically arranged. The growth parameters, including the growth temperature, growth time and plasma power, are systematically studied and optimized. Most importantly, the function of plasma has been revealed. In the same deposition machine, we have altered the plasma electrode and heater configurations, and found that the vertical graphene can only grow in local plasma environment. That is, the samples have to be well immersed in the plasma sheath electric field. In this way, the vertical growth of graphene and the local enhancement of electric field can form a positive feedback loop, resulting in the continuous growth of vertical graphene. This experiment clarifies the function of plasma electric field in the vertical graphene growth, and can offer hints for the growth of other vertical two-dimensional materials as well. The vertical graphene films are scalable, transfer-free and lithographically patternable, which is compatible with standard semiconductor processing and promising for optoelectronic applications. We have characterized the optical properties of the as-grown vertical graphene films, where a nearly zero transmittance is observed for 1100–2600nm wavelengths, indicating a superstrong absorption in the black colored vertical graphene.

In this work, the azo dye Congo red (CR) was degraded by a Fe–In₂O₃ catalyst under the irradiation of ultrasonic. The Fe–In₂O₃ catalyst was prepared by a fast and moderate solvothermal method followed by the characterization of X-ray diffraction and scanning electron microscope. The effects of operating parameters, such as catalyst composition, catalyst dosage, initial dye concentration, ultrasonic power and ultrasonic frequency on degradation process were discussed. In the experiment, the optimum CR removal of 97.75% in 60min was achieved under the conditions, i.e., catalyst dosage of 0.06$\mathrm{\text{g}}\cdot L^{-1}$, CR concentration of 10$\mathrm{\text{mg}}\cdot {\mathrm{\text{L}}}^{-1}$, ultrasonic frequency of 45kHz and ultrasonic power of 100W. Besides, the CR degradation behavior by the catalyst with ultrasonic is well in accordance with the first-order kinetic model.

In this study, green cellulose nanofibers-based composites were successfully prepared for efficient wide-band electromagnetic absorber to realize functional and high-value diversified utilization of cellulose nanofibers. Specifically, by the introduction of reduced graphene oxide (RGO) and flower-like copper sulfide (CuS) into CNFs used as raw material, CNFs/RGO/CuS porous composite microwave absorber were obtained. The CNFs/RGO/CuS porous composite exhibited excellent microwave absorption performance due to its unique three-dimensional porous flower-like structure and heterogeneous interface, which provided excellent impedance matching and attenuation capabilities. The fabricated CNFs/RGO/CuS composite exhibited a minimum reflection loss (RLmin) of $-$49.71dB at 11.52 GHz and a maximum absorption bandwidth of 5.30 GHz (from 10.40 GHz to 15.70 GHz) at only 2.50mm. In addition, the scanning electron microscope (SEM) results showed that the CNFs/RGO/CuS composite had a porous microstructure. And the Brunauer–Emmett–Teller (BET) specific surface area of the CNFs/RGO/CuS composite was 326.46m²/g. Potential absorption mechanisms were proposed considering the interfacial polarization, impedance matching, and dielectric losses caused by the synergistic effects among CNFs, RGO, and CuS. This work proposed a new strategy to biomass-based functional materials, and used the natural polymer CNFs, compounded with reduced graphene oxide and copper sulfide, to achieve efficient microwave absorbing materials.

All-inorganic halide perovskite (CsPbX₃) is a photoelectric material with great potential. However, the Pb element in CsPbX₃ is toxic, which affects the further use of these materials. The toxicity problem can be solved by adding Zn ions into CsPbBr₃. In this work, Zn-doped cesium lead bromide perovskites (CsPbBr₃) nanocrystals (NCs) were synthesized by thermal injection method, and their optical properties were also studied. When Zn was introduced into CsPbBr₃, its exciton emission summit shifts slightly. By changing the concentration of Zn${}^{2+}$, the size and optical properties of Zn:CsPbBr₃ NCs can be controlled. We also study the decay lifetime of its emission peak, and the results showed that Zn:CsPbBr₃ had a longer PL decay lifetime than undoped CsPbBr₃. This indicated that the incorporation of CsPbBr₃ into Zn${}^{2+}$ had a good application prospect in the optical field.