Nanowires for Biosensing: Lightguiding of Fluorescence as a Function of Diameter and Wavelength

Abstract

Semiconductor nanowires can act as nanoscaled optical fibers, enabling them to guide and concentrate light emitted by surface-bound fluorophores, potentially enhancing the sensitivity of optical biosensing. While parameters such as the nanowire geometry and the fluorophore wavelength can be expected to strongly influence this lightguiding effect, no detailed description of their effect on in-coupling of fluorescent emission is available to date. Here, we use confocal imaging to quantify the lightguiding effect in GaP nanowires as a function of nanowire geometry and light wavelength. Using a combination of finite-difference time-domain simulations and analytical approaches, we identify the role of multiple waveguide modes for the observed lightguiding. The normalized frequency parameter, based on the step-index approximation, predicts the lightguiding ability of the nanowires as a function of diameter and fluorophore wavelength, providing a useful guide for the design of optical biosensors based on nanowires.

Quantitative analysis of time-resolved RHEED during growth of vertical nanowires

“…Semiconductor nanowires (NWs) are promising building blocks for future devices like transistors, 1,2 light-emitting diodes (LEDs), 3 lasers, 4 solar cells 5,6 or sensors. 7,8 The synthesis of semiconductor NWs is often realized by the vapourliquid-solid (VLS) growth, which involves a liquid metal droplet on top of the growing NWs. In various material systems, like e.g.…”

Diameter-optimized high-order waveguide nanorods for fluorescence enhancement applied in ultrasensitive bioassays

“…have been successfully fabricated and studied. [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] Amongst them, ZnO NRs-based FE platforms are particularly fascinating in bioassays, thanks to their well-recognized benefits, such as prevention from fluorescence quenching, no optical absorption in the entire visible to near-infrared region, relatively large refractive index, controllable morphology and alignment, facile fabrication, and low cost. [37][38][39][40] It is therefore no surprise that enormous effort has been devoted to improve the detection performance of ZnO NRs-based FE platforms through various morphology and surface/interface modification.…”

Nanostructured Architectures for Biomolecular Detection inside and outside the Cell

“…In this configuration, silicon nanowires can act as optical fibers to concentrate and guide fluorophore emissions, enabling them to be used as optical biosensors. [38] Silicon nanowires have been commonly paired with field effect transistors (FETs) to achieve label-free (in addition to rapid and sensitive) detection of biomolecules. [39] Due to their excellent electrical properties, silicon nanowire-FETs have been used to measure electrophysiological activities in cells and cell networks, including neurons, cardiomyocytes, and muscle cells.…”

“…Reproduced with permission. [38] Copyright 2018, American Chemical Society. c) Silicon nanowires vertically oriented on surfaces can be used as capturing needles to extract specific target proteins from live cells and release the cell after capture.…”