Single Particle Nanoplasmonic Sensing in Individual Nanofluidic Channels

Paper in proceeding, 2017

By combining the precise mass transport control of nanofluidics with the single particle sensing abilities of nanoplasmonics we demonstrate real time single particle parallel readout of multiple nanofluidic channels from the same chip using plasmonic nanospectroscopy. The exceptional label-free sensitivity of individual plasmonic nanoparticles combined with dark-field scattering spectroscopy has proven to be a powerful tool in catalysis[1], materials science[2], and gas sensing[3], as well as to detect single molecular binding events[4]. However, despite the proven sensitivity of single particle plasmonic nanosensors, the detection of ultralow concentrations of specific analyte molecules is limited by the fact that they usually are free to diffuse away from the sensing surface, which gives rise to unpractical detection times on the order of days. As a first step to alleviate this limitation, we present an integrated nanoplasmonic-nanofluidic platform comprised of nanochannels integrated with a single plasmonic nanoantenna sensor, schematically presented in Fig 1. The dimensions of the nanofluidic system are chosen such that the entire volume of analyte solution is forced to pass the plasmonic sensor within the decay length of the near field, in order to significantly enhance the probability of direct interaction of the sensor surface with analyte in the channel. The developed devices enable on-chip referenced parallel single particle nanoplasmonic sensing inside multiple individual nanofluidic channels with dimensions down to the 100 nm range. Beyond detailed discussion of the nanofabrication, general device characterization, and parallelized single particle plasmonic readout concepts, we present the device function on two examples: (i) in situ measurements of local buffer concentrations inside a nanofluidic channel; (ii) real time binding kinetics of alkanethiol molecules to a single plasmonic nanoantenna sensor in a single nanochannel.