Fluorescent Biosensors Based on Silicon Nanowires

Nanostructures are arising as novel biosensing platforms promising to surpass current performance in terms of sensitivity, selectivity, and affordability of standard approaches. However, for several nanosensors, the material and synthesis used make the industrial transfer of such technologies complex. Silicon nanowires (NWs) are compatible with Si-based flat architecture fabrication and arise as a hopeful solution to couple their interesting physical properties and surface-to-volume ratio to an easy commercial transfer. Among all the transduction methods, fluorescent probes and sensors emerge as some of the most used approaches thanks to their easy data interpretation, measure affordability, and real-time in situ analysis. In fluorescent sensors, Si NWs are employed as substrate and coupled with several fluorophores, NWs can be used as quenchers in stem-loop configuration, and have recently been used for direct fluorescent sensing. In this review, an overview on fluorescent sensors based on Si NWs is presented, analyzing the literature of the field and highlighting the advantages and drawbacks for each strategy.

Nanoneedle-Based Sensing in Biological Systems

Nanoneedles are high aspect ratio nanostructures with a unique biointerface. Thanks to their peculiar yet poorly understood interaction with cells, they very effectively sense intracellular conditions, typically with lower toxicity and perturbation than traditionally available probes. Through long-term, reversible interfacing with cells, nanoneedles can monitor biological functions over the course of several days. Their nanoscale dimension and the assembly into large-scale, ordered, dense arrays enable monitoring the functions of large cell populations, to provide functional maps with submicron spatial resolution. Intracellularly, they sense electrical activity of complex excitable networks, as well as concentration, function, and interaction of biomolecules in situ, while extracellularly they can measure the forces exerted by cells with piconewton detection limits, or efficiently sort rare cells based on their membrane receptors. Nanoneedles can investigate the function of many biological systems, ranging from cells, to biological fluids, to tissues and living organisms. This review examines the devices, strategies, and workflows developed to use nanoneedles for sensing in biological systems.

Silicon nanowire heterostructures for advanced energy and environmental applications: a review

Semiconductor nanowires (NWs), in particular Si NWs, have attracted much attention in the last decade for their unique electronic properties and potential applications in several emerging areas. With the introduction of heterostructures (HSs) on NWs, new functionalities are obtained and the device performance is improved significantly in many cases. Due to the easy fabrication techniques, excellent optoelectronic properties and compatibility of forming HSs with different inorganic/organic materials, Si NW HSs have been utilized in various configurations and device architectures. Herein, we review the recent developments in Si NW HS-based devices including the fabrication techniques, properties (e.g., light emitting, antireflective, photocatalytic, electrical, photovoltaic, sensing etc) and related emerging applications in energy generation, conversion, storage, and environmental cleaning and monitoring. In particular, recent advances in Si NW HS-based solar photovoltaics, light-emitting devices, thermoelectrics, Li-ion batteries, supercapacitors, hydrogen generation, artificial photosynthesis, photocatalytic degradation of organic dyes in water treatment, chemical and gas sensors, biomolecular sensors for microbial monitoring etc have been addressed in detail. The problems and challenges in utilizing Si NW HSs in device applications and the key parameters to improve the device performance are pointed out. The recent trends in the commercial applications of Si NW HS-based devices and future outlook of the field are presented at the end.