Jeremy Campbell

The potential of diatom nanobiotechnology for applications in solar cells, batteries, and electroluminescent devices

The ability to produce low-cost, hierarchically-structured and nanopatterned inorganic materials could potentially revolutionize the way we fabricate photovoltaic, energy storage, and optoelectronic devices. In nature, many organisms carry out the hierarchical assembly of metal oxide materials through cellular and biochemical processes that replicate periodic micro- and nanoscale features by a bottom-up approach at ambient conditions. For example, single-celled algae called diatoms produce a nanostructured amorphous silica skeleton called a frustule. The insertion of other metal oxide materials such as titanium or germanium dioxide into the nanostructure of the diatom frustule could potentially be utilized to fabricate new dye-sensitized solar cells, nanostructured battery electrodes, and electroluminescent display devices. The exploitation of diatom nanobiotechnology for the development of novel device concepts in these areas is overviewed.

Enhancing surface plasmon resonances of metallic nanoparticles by diatom biosilica

Diatoms are single-celled algaes that make photonic-crystal-like silica shells or frustules with hierarchical micro- & nano-scale features consisting of two-dimensional periodic pores. This article reports the use of diatom frustules as an integration platform to enhance localized surface plasmon resonances of self-assembled silver nanoparticles (NPs) on the surface of diatom frustules. Theoretical and experimental results show enhanced localized surface plasmons due to the coupling with the guided-mode resonances of the frustules. We observed 2 × stronger optical extinction and over 4 × higher sensitivity of surface-enhanced Raman scattering of Rhodmine 6G from the NPs-on-diatom than the NPs-on-glass structure.

Ultra-sensitive immunoassay biosensors using hybrid plasmonic-biosilica nanostructured materials

We experimentally demonstrate an ultra-sensitive immunoassay biosensor using diatom biosilica with self-assembled plasmonic nanoparticles. As the nature-created photonic crystal structures, diatoms have been adopted to enhance surface plasmon resonances of metal nanoparticles on the surfaces of diatom frustules and to increase the sensitivity of surface-enhanced Raman scattering (SERS). In this study, a sandwich SERS immunoassay is developed based on the hybrid plasmonic-biosilica nanostructured materials that are functionalized with goat anti-mouse IgG. Our experimental results show that diatom frustules improve the detection limit of mouse IgG to 10 pg/mL, which is ˜100× better than conventional colloidal SERS sensors on flat glass. Ultra-sensitive immunoassay biosensor using diatom biosilica with self-assembled plasmonic nanoparticles.

Surface-Enhanced Raman Spectroscopy Sensors From Nanobiosilica With Self-Assembled Plasmonic Nanoparticles

We present an innovative surface-enhanced Raman spectroscopy (SERS) sensor based on a biological-plasmonic hybrid nanostructure by self-assembling silver (Ag) nanoparticles into diatom frustules. The photonic-crystal-like diatom frustules provide a spatially confined electric field with enhanced intensity that can form hybrid photonic-plasmonic modes through the optical coupling with Ag nanoparticles. The experimental results demonstrate 4-6× and 9-12× improvement of sensitivities to detect the Raman dye for resonance and nonresonance SERS sensing, respectively. Such low-cost and high-sensitivity SERS sensors have significant potentials for label-free biosensing.

Surface-enhanced Raman scattering on diatom biosilica photonic crystals

Diatoms are a group of single-celled photosynthetic algae that make skeletal shells of hydrated amorphous silica, called frustules, which possess hierarchical nanoscale photonic crystal features made by a bottom-up approach at ambient temperature and pressure. In this paper, we theoretically investigate electric field enhancements of plasmonic nanoparticles coated on the surface of diatom skeletal shells. Surface-Enhanced Raman Scattering substrates are prepared by evaporating 10 nm thick silver film and self-assembling silver nanoparticles on diatom surfaces, which show significantly better SERS signals than silver nanoparticles on flat glass substrates.

Label-free optical sensing on hybrid plasmonic-nanobiosilica platforms

Diatoms are single-celled algaes that make photonic-crystal-like silica shells or frustules with hierarchical micro- and nano-scale features consisting of two-dimensional periodic pores. In this paper, we present an innovative label-free optical sensor based on a biological-plasmonic hybrid nanostructure by self-assembling silver (Ag) nanoparticles into diatom frustules. The photonic-crystal-like diatom frustules provide a spatially confined electric field with enhanced intensity that can form hybrid photonic-plasmonic modes through the optical coupling with Ag nanoparticles. The experimental results demonstrate 4-6x and 9-12x improvement of sensitivities to detect the Raman dye for resonance and nonresonance SERS sensing, respectively.

Integration of biological photonic crystals in dye-sensitized solar cells for enhanced photocurrent generation

Dye-sensitized solar cells (DSSCs) rely on a network of titanium dioxide nanoparticles for electron transport and must balance carrier generation and collection. Adding photonic structures may increase light capture without affecting carrier collection. Diatoms are single-celled algae that biologically fabricate silicon dioxide cell walls which resemble photonic crystal slabs. We present a simple fabrication strategy that allows for uniform and controlled placement of biosilica within DSSCs. Integration of biosilica reduces photoanode transmittance to less than 5% prior to dye sensitization at loading levels as low as 6 wt% biosilica. Increased biosilica loading (17 wt%) provides additional enhancements in photocurrent generation. Reflectance measurements suggest that the enhancement results from the combined effects of photonic resonance and Mie scattering. Overall efficiency of these devices is improved by 8% and 14%, respectively.

Novel form of photonic crystals for bioimaging contrast enhancement

We report here a diatom frustule-based photonic structure acting as an efficient near infrared contrast agent. The frustule of diatom Pinnularia sp. consists of two valves with same exquisite fine 2D periodicity at the submicron scale, similar to a 2D photonic crystal. Decoration of diatom frustules with higher refractive index materials leads to a refractive indices contrast increase between the array of pores and the frame. Our calculation and measurements show that magnetite nanoparticle-decorated diatom frustules have a wide pseudo photonic band gap in near infrared range, resulting in a strong near infrared reflection. It allows the magnetite nanoparticle-decorated diatom frustules to be imaged with a high optical coherence tomography contrast.