Detecting explosive molecules from nanoliter solution: A new paradigm of SERS sensing on hydrophilic photonic crystal biosilica

Abstract

We demonstrate a photonic crystal biosilica surface-enhanced Raman scattering (SERS) substrate based on a diatom frustule with in-situ synthesized silver nanoparticles (Ag NPs) to detect explosive molecules from nanoliter (nL) solution. By integrating high density Ag NPs inside the nanopores of diatom biosilica, which is not achievable by traditional self-assembly techniques, we obtained ultra-high SERS sensitivity due to dual enhancement mechanisms. First, the hybrid plasmonic-photonic crystal biosilica with three dimensional morphologies was obtained by electroless-deposited Ag seeds at nanometer sized diatom frustule surface, which provides high density hot spots as well as strongly coupled optical resonances with the photonic crystal structure of diatom frustules. Second, we discovered that the evaporation-driven microscopic flow combined with the strong hydrophilic surface of diatom frustules is capable of concentrating the analyte molecules, which offers a simple yet effective mechanism to accelerate the mass transport into the SERS substrate. Using the inkjet printing technology, we are able to deliver multiple 100 pico-liter (pL) volume droplets with pinpoint accuracy into a single diatom frustule with dimension around 30 μm × 7 μm × 5 μm, which allows for label-free detection of explosive molecules such as trinitrotoluene (TNT) down to 10−10 M in concentration and 2.7 × 10−15 g in mass from 120 nL solution. Our research illustrates a new paradigm of SERS sensing to detect trace level of chemical compounds from minimum volume of analyte using nature created photonic crystal biosilica materials.

Chemical and Biological Sensing Using Diatom Photonic Crystal Biosilica With In-Situ Growth Plasmonic Nanoparticles

“…After Ag seed deposition, the diatom frustules were immersed in 1.5 mL of growth media (1 mL of 5 mM AgNO 3 and 0.5 mL of 50 mM ascorbic acid). The size and density of the Ag nanoparticles could be well controlled as we recently reported [35]. It is clearly seen that high density Ag NPs with diameters around 40 nm were deposited on the surface of the diatom frustule.…”

“…We can see that in both hot spots, |E| 4 has a broadband enhancement around 532 nm. The SERS enhancement factor of the hybrid diatom-Ag NPs is around 10 9 [35], which is nearly two orders of magnitude higher than some well-defined SERS substrates [38], [39]. …”

Plasmonic nanoparticles‐decorated diatomite biosilica: extending the horizon of on‐chip chromatography and label‐free biosensing

“…modified the diatom frustules ( Coscinodiscus concinnus ) chemically and then attached antibodies as a highly‐selective bioprobe for immunocomplex biosensing . Our previous studies have proved that metallic nanoparticles (NPs) located near or inside the periodic nanopores of diatoms can form hybrid photonic‐plasmonic modes via theoretical analysis and experimental results . These photonic‐plasmonic modes further increase the local optical field near the plasmonic NPs and additional SERS enhancement was achieved.…”

Advances in optoplasmonic sensors – combining optical nano/microcavities and photonic crystals with plasmonic nanostructures and nanoparticles

“…Extreme, sub-attomolar detection of a streptavidin protein was reported for nanoslot PhC nanolasers [139,[161][162][163][164][165][166][167][168], while novel PhC nanocavities combined with plasmonic nanostructures have emerged as hybrid photonic-plasmonic biosensors [169][170][171][172][173][174][175][176][177][178][179]. Unusually sensitive biodetection down to the single-molecule level with nanostructured materials comprising selfassembled silver nanoparticles on PhC diatom biosilica [180,181] and a gold antenna-in-a-nanocavity [182] substantiates the fast and steady advancement of hybrid photonic-plasmonic instrumentation utilising PhCs.…”

“…It is conceivable that these 3D metamaterials could be merged with more intricate 3D PBG cavities ( Figure 32C) to ameliorate biodetection limits [197]. A few of the latest developments in hybrid photonicplasmonic apparatuses, involving PhCs, have arrived at ascertaining single-molecule signatures [180][181][182]. Selfassembled silver nanoparticles on diatom PhC biosilica, visible in Figure 33, is a shining example [180].…”