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.

Biosensing platforms based on silicon nanostructures: A critical review

Biosensors are revolutionizing the health-care systems worldwide, permitting to survey several diseases, even at their early stage, by using different biomolecules such as proteins, DNA, and other biomarkers. However, these sensing approaches are still scarcely diffused outside the specialized medical and research facilities. Silicon is the undiscussed leader of the whole microelectronics industry, and novel sensors based on this material may completely change the health-care scenario. In this review, we will show how novel sensing platforms based on Si nanostructures may have a disruptive impact on applications with a real commercial transfer. A critical study for the main Si-based biosensors is herein presented with a comparison of their advantages and drawbacks. The most appealing sensing devices are discussed, starting from electronic transducers, with Si nanowires field-effect transistor (FET) and porous Si, to their optical alternatives, such as effective optical thickness porous silicon, photonic crystals, luminescent Si quantum dots, and finally luminescent Si NWs. All these sensors are investigated in terms of working principle, sensitivity, and selectivity with a specific focus on the possibility of their industrial transfer, and which ones may be preferred for a medical device.

Wafer-Scale Synthesized MoS2/Porous Silicon Nanostructures for Efficient and Selective Ethanol Sensing at Room Temperature

This paper presents the performance of a highly selective ethanol sensor based on MoS₂-functionalized porous silicon (PSi). The uniqueness of the sensor includes its method of fabrication, wafer scalability, affinity for ethanol, and high sensitivity. MoS₂ nanoflakes (NFs) were synthesized by sulfurization of oxidized radio-frequency (RF)-sputtered Mo thin films. The MoS₂ NFs synthesis technique is superior in comparison to other methods, because it is chip-scalable and low in cost. Interdigitated electrodes (IDEs) were used to record resistive measurements from MoS₂/PSi sensors in the presence of volatile organic compound (VOC) and moisture at room temperature. With the effect of MoS₂ on PSi, an enhancement in sensitivity and a selective response for ethanol were observed, with a minimum detection limit of 1 ppm. The ethanol sensitivity was found to increase by a factor of 5, in comparison to the single-layer counterpart levels. This impressive response is explained on the basis of an analytical resistive model, the band gap of MoS₂/PSi/Si, the interface formed between MoS₂ and PSi, and the chemical interaction of the vapor molecules and the surface. This two-dimensional (2D) composite material with PSi paves the way for efficient, highly responsive, and stable sensors.