Cargo inspection apparatus having a nanoparticle film and method of use thereof

1. A cargo inspection apparatus for the inspection of an analyte carried by a medium, the apparatus comprising:

a housing having an inlet allowing for entry of the medium and an outlet allowing for exit of the medium; and

an adsorber disposed within the housing in fluid communication with the medium flow from the inlet to the outlet, the adsorber comprising a substrate having disposed thereon a nanoparticle film;

wherein the nanoparticle film comprises nanoparticles having an average particle size of equal to or less than about 500 nanometers.

2. The apparatus of claim 1 , wherein the nanoparticles have an average particle size of about 50 nanometers.

3. The apparatus of claim 1 , wherein the nanoparticles comprise a metal.

4. The apparatus of claim 3 , wherein the metal is copper, gold, platinum, palladium, aluminum, iron, titanium, vanadium, chromium, nickel, silver, tantalum, tungsten, tin, gallium, germanium, or a combination comprising at least one of the foregoing metals.

5. The apparatus of claim 3 , wherein the metal comprises gold.

6. The apparatus of claim 1 , wherein the nanoparticle film is a monolayer.

7. The apparatus of claim 1 , wherein the adsorber is oriented at an angle relative to the direction of medium flow at the inlet, the nanoparticle film being oriented toward the inlet.

8. The apparatus of claim 1 , wherein the medium comprises air.

9. The apparatus of claim 1 , further comprising a filtration membrane disposed at the inlet, at the outlet, or at both the inlet and the outlet, the filtration membrane being discriminative of particles entering the housing having a particle size equal to or greater than an order of magnitude of about 10 2 micrometers.

10. The apparatus of claim 1 , wherein the nanoparticle film is made from the method comprising:

dispersing nanoparticles in a first liquid;

adding a second liquid to the first liquid to form a nanoparticle film on top of a solution comprising the first liquid, the second liquid and the nanoparticles, wherein the second liquid has a dielectric constant that is different from a dielectric constant of the first liquid; and

contacting the substrate with the solution to deposit the nanoparticle film onto the contacted portion of the substrate.

11. The apparatus of claim 10 , wherein:

the nanoparticles comprise gold;

the first liquid comprises water;

the second liquid comprises ethanol; and

the substrate comprises silica.

12. The apparatus of claim 1 , further comprising:

a laser and a raman spectrometer each in signal communication with the nanoparticle film allowing for real time inspection of the analyte.

13. The apparatus of claim 1 , wherein the adsorber is removably connected to the housing.

14. A method for detecting an analyte in a cargo hold, the analyte being carried by a medium, the method comprising:

positioning within the cargo hold an inspection apparatus comprising a housing having an inlet allowing for entry of the medium and an outlet allowing for exit of the medium, and an adsorber disposed within the housing in fluid communication with the medium flow from the inlet to the outlet, the adsorber comprising a substrate having disposed thereon a nanoparticle film, the nanoparticle film comprising nanoparticles having an average particle size of equal to or less than about 500 nanometers;

allowing for the adsorption of the analyte at the nanoparticle film; and

performing surface enhanced Raman spectroscopy to determine the identity of the analyte.

15. The method of claim 14 , wherein:

the substrate comprises silica; and

the nanoparticles comprise gold.

16. The method of claim 15 , wherein the nanoparticles have an average particle size of equal to or less than about 50 nanometers.

17. The method of claim 14 , wherein:

the surface enhanced Raman spectroscopy is detectably responsive to the presence of the analyte in a solution of the analyte in a concentration of less than or equal to about the part per million regime (10 −6 ).

18. The method of claim 14 , wherein:

the surface enhanced Raman spectroscopy is detectably responsive to the presence of the analyte in a solution of the analyte in a concentration of less than or equal to about the part per billion regime (10 −9 ).