ConspectusSensors are ubiquitous, and
their importance
is only going to increase
across many areas of modern technology. In this respect, hydrogen
gas (H2) sensors are no exception since they allow mitigation
of the inherent safety risks associated with mixtures of H2and air. The deployment of H2technologies is rapidly
accelerating in emerging energy, transport, and green steel-making
sectors, where not only safety but also process monitoring sensors
are in high demand. To meet this demand, cost-effective and scalable
routes for mass production of sensing materials are required. Here,
the state-of-the-art often resorts to processes derived from the microelectronics
industry where surface-based micro- and nanofabrication are the methods
of choice and where (H2) sensor manufacturing is no exception.In this Account, we discuss how our recent efforts to develop sensors
based on plasmonic plastics may complement the current state-of-the-art.
We explore a new H2sensor paradigm, established through
a series of recent publications, that combines (i) the plasmonic optical
H2detection principle and (ii) bulk-processed nanocomposite
materials. In particular, plasmonic plastic nanocomposite sensing
materials are described that comprise plasmonic H2-sensitive
colloidally synthesized nanoparticles dispersed in a polymer matrix
and enable the additive manufacturing of H2sensors in
a cost-effective and scalable way. We first discuss the concept of
plasmonic plastic nanocomposite materials for the additive manufacturing
of an active plasmonic sensing material on the basis of the three
key components that require individual and concerted optimization:
(i) the plasmonic sensing metal nanoparticles, (ii) the surfactant/stabilizer
molecules on the nanoparticle surface from colloidal synthesis, and
(iii) the polymer matrix. We then introduce the working principle
of plasmonic H2detection, which relies on the selective
absorption of H species into hydride-forming metal nanoparticles that,
in turn, induces distinct changes in their optical plasmonic signature
in proportion to the H2concentration in the local atmosphere.
Subsequently, we assess the roles of the key components of a plasmonic
plastic for H2sensing, where we have established that
(i) alloying Pd with Au and Cu eliminates hysteresis and introduces
intrinsic deactivation resistance at ambient conditions, (ii) surfactant/stabilizer
molecules can significantly accelerate and decelerate H2sorption and thus sensor response, and (iii) polymer coatings accelerate
sensor response, reduce the limit of detection (LoD), and enable molecular
filtering for sensor operation in chemically challenging environments.
Based on these insights, we discuss the rational development and detailed
characterization of bulk-processed plasmonic plastics based on glassy
and fluorinated matrix polymers and on tailored flow-chemistry-based
synthesis of Pd and PdAu alloy colloidal nanoparticles with optimized
stabilizer molecules. In their champion implementation, they enable
highly stable H2sensors with response times in the 2 s
range and an LoD of few 10 ppm of H2. To put plasmonic
plastics in a wider perspective, we also report their implementation
using different polymer matrix materials that can be used for 3D printing
and (an)isotropic Au nanoparticles that enable the manufacturing of
macroscopic plasmonic objects with, if required, dichroic optical
properties and in amounts that can be readily upscaled. We advertise
that melt processing of plasmonic plastic nanocomposites is a viable
route toward the realization of plasmonic objects and sensors, produced
by scalable colloidal synthesis and additive manufacturing techniques.