材料科学最新文献

Surface-enhanced Raman spectroscopy (SERS) using gold-nanorod-dimer nanoantennas has shown great potential in various applications. This reflects in their large values of the customary figure of merit of SERS: the enhancement factor (EF), which is essentially the fourth power of the electric field integrated at the gap, the location at which target molecules are to be sensed. However, fabrication errors in the nanorod lengths can lead to significant variations in the enhancement factor, resulting in performance limitations whenever low values of EF are encountered. Here, we report both design and procedural strategies to address this issue. First, we show that by reducing the nanorod diameter from 360 to 260 nm, the EF minima can be avoided for any nanorod length, mitigating the impact of fabrication errors. In addition, we explore the influence of incident wave polarization and orientation on the EF. Our simulations reveal that by tilting the excitation away from normal incidence, it is possible to substantially enhance EF under conditions that would otherwise exhibit low enhancement. In particular, this includes the case of 360 nm diameter. These findings expand the fabrication tolerance and broaden the range of usability of gold-nanorod-dimer nanoantennas, enabling more robust and reliable SERS performance. Importantly, we also show that these strategies also apply to nanoantennas with covered nanorod ends, which are of particular interest for realizing hybrid devices that combine SERS with electrical transport measurements.

Silver nanoparticles (AgNPs) are increasingly recognized for their potential in biomedical and environmental applications such as antimicrobial, anticancer, and drug delivery properties. But their widespread use is a source of concern with regard to toxicity. The primary toxicological effects of AgNPs are due to oxidative stress causing cellular damage, DNA damage and mitochondrial dysfunction. The interaction of these AgNPs with cellular membranes generates reactive oxidative species (ROS) and interferes with homeostatic redox balance and induces the apoptotic pathway. AgNPs toxicity is influenced by many factors, including particle size, surface modification and synthesis method. Typically, smaller AgNPs are more toxic; however, surface modifications with biocompatible agents can reduce some of the harmful effects. Possibilities of creating AgNPs with lower toxicities using green synthesis methods through plant extracts and other natural agents are promising. However, while these developments are important, more effort is needed to fully understand how AgNPs exert their toxicity, assess various aspects of their safety and optimize their use for therapeutic or industrial purposes. Environmental impacts and a deeper knowledge of human health risks, in particular, chronic effects, are important future research areas.

Graphical Abstract

Silver nanoparticles induced cytotoxicity

Incremental sheet metal forming (ISF) process is an established agile forming method wherein the blank of the sheet metal is deformed into a preferred geometric by the sequence of bit-by-bit local deformation produced by the forming tool. There is no need for a die to shape the sheet metal, which is the principal strength of this process. The review made on the ISF process and particularly the different deformation mechanisms that are generated on the sheet metal during the ISF process are discussed broadly in this paper. The effects of this deformation mechanism on the ISF process are also discussed. The recent developments in ISF processes, such as Heat Assisted ISF process, Water Jet ISF process, Electromagnetic ISF process for sheet metals and Multi-stage ISF process, are also discussed in detail. Each of these processes possesses its distinct merits and demerits which are also listed. The ISF process is performed on different materials that were also discussed.

Herein, we designed a special screen-printing carbon electrode system with two independent zones to realize the immobilization of two kinds of aptamers on electrode surface. Nb₄C₃-MXene is a remarkable member from MX₃ MXene with many excellent properties. In this study, Nb₄C₃-MXene nanosheets were firstly modified onto the screen-printing carbon electrode surface as the substrate materials to offer big surface area and then gold nanoparticles were loaded onto the surface of Nb₄C₃-MXene nanosheets through electrodeposition. Afterward, the aptamer-containing double-stranded DNA was spontaneously assembled onto the modified electrode surface through the Au–S bond. Owing to high affinity of aptamers towards the heavy metal ions (Cd²⁺ and Pb²⁺ in this case), the aptamers tagged with methylene blue and ferrocene would specifically bond with heavy metal ions to form folded structures and competed off from the electrode surface, and then the change of electrochemical signals can be detected by square wave voltammetry. The aptasensor exhibits a good linear response towards Cd²⁺ and Pb²⁺ from 1 × 10⁻¹⁰ to 1 × 10⁻⁷ M, and their detection limits are 59.8 pM of Pb²⁺ and Cd²⁺ of 146.2 pM; LOQ are 93.7 pM of Pb²⁺ and 164.8 pM of Cd²⁺, respectively.