Optical molecular nanowire sensor and method
An analyte detection system includes a substrate, a nanowire positioned on the substrate, the nanowire configured to bind with an analyte and a fluorophore, an excitation radiation source configured to irradiate the nanowire with excitation radiation, and a radiation detection device configured to collect radiation emitted by the fluorophore and output from the free end of the nanowire. The substrate may be a reflective substrate, a numerical aperture (NA) of the excitation radiation source may be 0.25 or less, and/or the nanowire may have a diameter D=M*λ/[Re(n(λ))], wherein 5.5≤M≤6.5, λ is a peak wavelength of the excitation radiation or a peak wavelength of the collected radiation, and Re(n(λ)) is a real part of a refractive index of the nanowire at peak wavelength λ.
1 . An analyte detection system, comprising:
a substrate;
a nanowire positioned on the substrate, the nanowire configured to bind with an analyte and a fluorophore;
an excitation radiation source configured to irradiate the nanowire with excitation radiation; and
a radiation detection device configured to collect radiation emitted by the fluorophore and output from the free end of the nanowire,
wherein the nanowire has a diameter D=about 0.6*λ/[Re(n(λ))], wherein λ is a peak wavelength of the collected radiation, and Re(n(λ)) is a real part of a refractive index of the nanowire at peak wavelength λ.
2 . The system of claim 1 , wherein:
the nanowire has a free end and an opposing fixed end that is attached to a top surface of the substrate;
the substrate is a reflective substrate; and
the reflective substrate is configured to reflect radiation output from the fixed end of the nanowire back towards the free end of the nanowire.
3 . The system of claim 2 , wherein the reflective substrate comprises Ag or Zn.
4 . The system of claim 1 , wherein a numerical aperture (NA) of the excitation radiation source is 0.25 or less.
5 . The system of claim 1 , further comprising an optically transparent insulating shell covering the nanowire.
6 . The system of claim 5 , further comprising a protective layer covering the top surface of the substrate,
wherein the nanowire extends through the protective layer.
7 . The method of claim 1 , wherein the detection structure further comprises an optically transparent insulating shell covering the nanowire.
8 . The method of claim 7 , wherein:
the detection structure further comprises a protective layer covering a top surface of the substrate; and
the nanowire extends through the protective layer.
9 . An analyte detection method, comprising:
exposing a detection structure of an analyte detection system to a fluid comprising an analyte, the detection structure comprising a substrate and a nanowire positioned on the substrate;
binding the analyte to the nanowire;
irradiating a fluorophore attached to the nanowire with excitation radiation;
collecting radiation that is emitted by the fluorophore and output from the nanowire; and
detecting the analyte based on the collected radiation,
wherein:
the nanowire has a diameter D=about 0.6*λ/[Re(n(λ))], wherein λ is a peak wavelength of the collected radiation, and Re(n(λ)) is a real part of a refractive index of the nanowire at λ.
10 . The method of claim 9 , wherein:
the substrate is a reflective substrate;
the radiation that is emitted by the fluorophore is provided into the nanowire which functions as a waveguide for the radiation; and
the reflective substrate reflects radiation output from a fixed end of the nanowire which is fixed to the reflective substrate back through the nanowire and out of an opposing free end of the nanowire to be collected.
11 . The method of claim 9 , wherein a numerical aperture of the excitation radiation source is 0.25 or less.
12 . The method of claim 9 , wherein:
the fluid comprises the fluorophores bound to the analyte; and
the binding the analyte comprises binding the analyte and the fluorophores to the nanowire.
13 . The method of claim 12 , wherein the fluorophores are bound to the analyte prior to the binding of the analyte to the nanowire.
14 . The method of claim 12 , wherein the fluorophores are bound to the nanowire prior to the binding of the analyte to the nanowire.
15 . A method of making an analyte detection system, comprising:
determining a peak wavelength λ corresponding to a peak emission wavelength of a selected fluorophore;
determining a real part [Re(n(λ))] of a refractive index of a selected nanowire material at the peak wavelength λ;
determining a nanowire diameter D using the equation:
D =about 0.6*λ/[Re( n (λ))]; and
attaching a nanowire to a substrate, the nanowire comprising the selected nanowire material and having the determined diameter D.
16 . The method of claim 15 , wherein the substrate is a reflective substrate configured to reflect radiation output from a fixed end of the nanowire back towards an opposing free end of the nanowire.