Equilibrium Plasmonic Mercury Sensing Apparatus and Methods

• US 20190310192A1
• Filed: 04/05/2019
• Published: 10/10/2019
• Est. Priority Date: 04/05/2018
• Status: Active Grant

• Current Assignee: Picoyune, LLC
• Original Assignee: Picoyune, LLC
• Inventors: James, Jay, Crosby, Jeffrey Scott
• Granted Patent: US 10,620,122 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 2021/8578 Gaseous flow IR analysers G01N21/8507
• CPC Class Codes: G01N 21/0332 with temperature control control of temperature G05D23/00; cryostats F17C3/08
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/554 detecting the surface plasmon resonance of nanostructured metals, e.g. localised surface plasmon resonance
• CPC Class Codes: G01N 33/0045 for Hg

Abstract

Apparatus and methods are provided for quantitative detection of mercury vapor in gas samples using a film of nanoparticles. The localized surface plasmon resonance (LSPR) of an amalgam nanoparticle is sensitive to adsorbed mercury mass. The equilibrium mass of mercury on a gold nanoparticle is a function of the surrounding vapor concentration and the temperature of the gold. A device that introduces a temperature-controlled gold nanoparticle film to a controlled flow of sample gas responds predictably to a given mercury vapor concentration when optically probed in situ. Controlling the temperature of the film allows for control of adsorption and desorption rates. Equilibrium plasmonic mercury detection, described herein, removes the cycling necessary for many gold-based mercury analyses. Methods are given for the operation and analysis of the temperature-stabilized gold nanoparticle mercury sensor. The disclosed mercury-detection apparatus and methods find use in a variety of applications, including, for example, mercury detecting applications.

Claims

1. A mercury detection system, comprising:

(a) a flow cell comprising a mercury sensor, wherein the mercury sensor comprises;

(i) a transparent substrate; and

(ii) a mercury-sensitive film on a surface region of the substrate, wherein the mercury-sensitive film comprises a plurality of gold-mercury amalgam nanoparticles;

(b) a light source configured for directing light through the transparent substrate to the mercury-sensitive film;

(c) a light detector configured for detecting a localized surface plasmon resonance (LSPR) signal from the mercury-sensitive film; and

(d) a temperature-control unit for maintaining the mercury-sensitive film at a substantially constant selected temperature;

wherein the system determines whether mercury is present in a sample based on a LSPR signal detected from the mercury-sensitive film.

2. The system of claim 1, further comprising a gas source in communication with the flow cell and configured to provide a flow of a gas through the flow cell.

3. The system of claim 2, wherein the sample is a gaseous sample.

4. The system of claim 1, wherein the light source comprises a visible light source.

5. The system of claim 1, wherein the system is configured to detect changes in optical absorbance in a single active band of the visible light spectrum.

6. The system of claim 1, wherein the light detector comprises a photodiode.

7. The system of claim 1, wherein the gold-mercury amalgam nanoparticles are substantially spherical in shape, and further wherein the gold-mercury amalgam nanoparticles have an average diameter within a range from 1 nm to 20 nm.

8. The system of claim 1, wherein the transparent substrate includes a second surface region that is substantially free of mercury-sensitive film, and wherein (a) the light source is configured for additionally directing light through the transparent substrate to the second surface region, (b) the detector is configured for additionally detecting a second signal from the second surface region, and (c) the system is configured to determine a ratio comprising (i) signal detected from the mercury-sensitive film and (ii) signal detected from the second surface region that is substantially free of mercury-sensitive film.

9. The system of claim 1, wherein the nanoparticles of the film are preconditioned to substantially preclude irreversible mercury adsorption during use with a sample at the selected temperature.

10. A method for determining whether mercury is present in a gaseous sample, the method comprising:

(a) contacting a sample to a mercury sensor comprising;

(i) a transparent substrate; and

(ii) a mercury-sensitive film on a surface region of the substrate, wherein the mercury-sensitive film comprises a plurality of gold-mercury amalgam nanoparticles;

(b) maintaining the mercury-sensitive film at a substantially constant selected temperature;

(c) while performing step (b);

(i) directing light through the transparent substrate to the mercury-sensitive film, and

(ii) detecting a localized surface plasmon resonance (LSPR) signal from the mercury-sensitive film; and

(d) determining whether mercury is present in the sample based on a LSPR signal detected from the mercury-sensitive film.

11. The method of claim 10, wherein step (d) includes monitoring changes in transmission through the mercury-sensitive film in a single band of the visible spectrum.

12. The method of claim 10, wherein step (d) includes integrating detected steady-state LSPR signal with time.

13. The method of claim 10, wherein the transparent substrate further comprises a second surface region that is substantially free of mercury-sensitive film, and wherein said method further comprises additionally directing light through the transparent substrate to the second surface region while detecting for a signal from the second surface region, and then determining a ratio of signal detected from the mercury-sensitive film and signal detected from the second surface region that is substantially free of mercury-sensitive film.

14. The method of claim 10, wherein the nanoparticles of the film are preconditioned to substantially preclude irreversible mercury adsorption during use with a sample at the selected temperature.

15. A process for manufacturing a mercury-sensitive film comprising a plurality of gold-mercury amalgam nanoparticles, comprising:

(a) supporting a gold-nanoparticle film on a transparent substrate;

(b) maintaining the gold-nanoparticle film at a substantially constant selected operating temperature;

(c) while performing step (b);

(i) exposing the gold-nanoparticle film to mercury vapor in air while detecting for a first localized surface plasmon resonance (LSPR) signal from the film, and allowing the first signal to stabilize;

then

(ii) exposing the gold-nanoparticle film to mercury free air while detecting for a second LSPR signal from the film and allowing the second signal to stabilize;

whereby the nanoparticles of the film are preconditioned to substantially preclude irreversible mercury adsorption during use with a sample at the selected operating temperature.

16. A product made by the process of claim 15.