Nanomaterial-based substrates for chemical sensors using surface enhanced raman spectroscopy

An apparatus for estimating a concentration of a chemical in a fluid passage, comprising:

• a substrate comprising a first layer of unaligned carbon nanotubes and a second layer of metal nanowires directly deposited on top of the first layer to coat the first layer, the carbon nanotubes of the first layer being filtered from a suspension and chemically cross-linked;
• an energy source for directing a beam of electromagnetic energy at a selected energy level at a fluid sample from the fluid passage on a surface of the substrate;
• a detector for measuring an energy level of radiation emitted from the fluid sample in response to the beam of electromagnetic energy;
• and
• a processor configured to:
• determine a Raman spectrum of the fluid sample from the energy level of the emitted radiation, and
• estimate the concentration of a selected chemical in the fluid sample based on the Raman spectrum.

A method for characterizing a corrosive chemical in a fluid flowing in a fluid passage, comprising:

• forming a substrate comprising a first layer made from unaligned carbon nanotubes filtered from a suspension and chemically cross-linked to form the first layer and a second layer of metal nanowires directly deposited on top of the first layer to coat the first layer;
• placing a sample of the fluid on the substrate;
• radiating the fluid sample with electromagnetic radiation at a selected energy level;
• measuring a Raman spectrum emitted from the fluid sample in response to the electromagnetic radiation;
• and
• characterizing a concentration of the corrosive chemical in the fluid sample from the Raman spectrum.