Carbon Nanotube (CNT)-Based Biosensors

This review focuses on recent advances in the application of carbon nanotubes (CNTs) for the development of sensors and biosensors. The paper discusses various configurations of these devices, including their integration in analytical devices. Carbon nanotube-based sensors have been developed for a broad range of applications including electrochemical sensors for food safety, optical sensors for heavy metal detection, and field-effect devices for virus detection. However, as yet there are only a few examples of carbon nanotube-based sensors that have reached the marketplace. Challenges still hamper the real-world application of carbon nanotube-based sensors, primarily, the integration of carbon nanotube sensing elements into analytical devices and fabrication on an industrial scale.

Cross-field optoelectronic modulation via inter-coupled ferroelectricity in 2D In2Se3

The ability to couple the in-plane (IP) and out-of-plane (OOP) dipole polarizations in ferroelectric In2Se3 makes it a promising material for multimodal memory and optoelectronic applications. Herein, we experimentally demonstrate the cross-field optoelectronic modulation in In2Se3 based field-effect devices. Surface potential measurements of In2Se3 based devices directly reveal the bidirectional dipole locking following high gate voltage pulses. The experimental evidence of hysteretic change in the IP electrical field facilitating a nonvolatile memory switch, was further explored by performing photocurrent measurements. Fabricated photodetectors presented multilevel photocurrent characteristics showing promise for nonvolatile memory and electro-optical applications.

Self-inhibition effect of metal incorporation in nanoscaled semiconductors

There has been a persistent effort to understand and control the incorporation of metal impurities in semiconductors at nanoscale, as it is important for semiconductor processing from growth, doping to making contact. Previously, the injection of metal atoms into nanoscaled semiconductor, with concentrations orders of magnitude higher than the equilibrium solid solubility, has been reported, which is often deemed to be detrimental. Here our theoretical exploration reveals that this colossal injection is because gold or aluminum atoms tend to substitute Si atoms and thus are not mobile in the lattice of Si. In contrast, the interstitial atoms in the Si lattice such as manganese (Mn) are expected to quickly diffuse out conveniently. Experimentally, we confirm the self-inhibition effect of Mn incorporation in nanoscaled silicon, as no metal atoms can be found in the body of silicon (below 1017 atoms per cm−3) by careful three-dimensional atomic mappings using highly focused ultraviolet-laser-assisted atom-probe tomography. As a result of self-inhibition effect of metal incorporation, the corresponding field-effect devices demonstrate superior transport properties. This finding of self-inhibition effect provides a missing piece for understanding the metal incorporation in semiconductor at nanoscale, which is critical not only for growing nanoscale building blocks, but also for designing and processing metal–semiconductor structures and fine-tuning their properties at nanoscale.

Field-Effect Sensors for Virus Detection: From Ebola to SARS-CoV-2 and Plant Viral Enhancers

Coronavirus disease 2019 (COVID-19) is a novel human infectious disease provoked by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Currently, no specific vaccines or drugs against COVID-19 are available. Therefore, early diagnosis and treatment are essential in order to slow the virus spread and to contain the disease outbreak. Hence, new diagnostic tests and devices for virus detection in clinical samples that are faster, more accurate and reliable, easier and cost-efficient than existing ones are needed. Due to the small sizes, fast response time, label-free operation without the need for expensive and time-consuming labeling steps, the possibility of real-time and multiplexed measurements, robustness and portability (point-of-care and on-site testing), biosensors based on semiconductor field-effect devices (FEDs) are one of the most attractive platforms for an electrical detection of charged biomolecules and bioparticles by their intrinsic charge. In this review, recent advances and key developments in the field of label-free detection of viruses (including plant viruses) with various types of FEDs are presented. In recent years, however, certain plant viruses have also attracted additional interest for biosensor layouts: Their repetitive protein subunits arranged at nanometric spacing can be employed for coupling functional molecules. If used as adapters on sensor chip surfaces, they allow an efficient immobilization of analyte-specific recognition and detector elements such as antibodies and enzymes at highest surface densities. The display on plant viral bionanoparticles may also lead to long-time stabilization of sensor molecules upon repeated uses and has the potential to increase sensor performance substantially, compared to conventional layouts. This has been demonstrated in different proof-of-concept biosensor devices. Therefore, richly available plant viral particles, non-pathogenic for animals or humans, might gain novel importance if applied in receptor layers of FEDs. These perspectives are explained and discussed with regard to future detection strategies for COVID-19 and related viral diseases.

Transition from a uni- to a bimodal interfacial charge distribution in $$\hbox {LaAlO}_3$$/$$\hbox {SrTiO}_3$$ upon cooling

We present a combined resonant soft X-ray reflectivity and electric transport study of $$\hbox {LaAlO}_3$$ LaAlO 3 /$$\hbox {SrTiO}_3$$ SrTiO 3 field effect devices. The depth profiles with atomic layer resolution that are obtained from the resonant reflectivity reveal a pronounced temperature dependence of the two-dimensional electron liquid at the $$\hbox {LaAlO}_3$$ LaAlO 3 /$$\hbox {SrTiO}_3$$ SrTiO 3 interface. At room temperature the corresponding electrons are located close to the interface, extending down to 4 unit cells into the $$\hbox {SrTiO}_3$$ SrTiO 3 substrate. Upon cooling, however, these interface electrons assume a bimodal depth distribution: They spread out deeper into the $$\hbox {SrTiO}_3$$ SrTiO 3 and split into two distinct parts, namely one close to the interface with a thickness of about 4 unit cells and another centered around 9 unit cells from the interface. The results are consistent with theoretical predictions based on oxygen vacancies at the surface of the $$\hbox {LaAlO}_3$$ LaAlO 3 film and support the notion of a complex interplay between structural and electronic degrees of freedom.