Engineering the Properties of Polymer Photonic Crystals with Mesoporous Silicon Templates

Abstract

The effect of molecular weight on the rate and extent of melt-infiltration of polystyrene into mesoporous silicon-based photonic crystals is investigated as a function of polymer molecular weight. Polymer viscosity and chain end-to-end (Ree) distance correlate with the rate and extent of infiltration. High molecular weight (Mw) polystyrene (200 or 400 kDa) infiltrates the mesoporous material in two distinct phases: a rapid phase where the larger pores of the template are filled, followed by a slower phase during which the smaller pores fill. Low molecular weight polystyrene (20 and 35 kDa) fills the pores more uniformly, progressing into the film as a single, relatively distinct front of liquid polymer. Scanning electron microscope (SEM) analyses of cross sections of the films are consistent with the optical measurements, showing a lower extent of infiltration for the higher molecular weight polymers. Removal of the porous Si templates by soaking in a chemical etchant generates free-standing films of nanostructured polymer. The low molecular weight samples display better replication. Partial removal of the template enables tuning of the hydrophobicity of the free-standing polymer films, which is demonstrated with a flexible and chemically stable polyvinylidene fluoride polymer

Nanoscale Photoluminescence Manipulation in Monolithic Porous Silicon Oxide Microcavity Coated with Rhodamine‐Labeled Polyelectrolyte via Electrostatic Nanoassembling

“…Furthermore, the lineshape of the reflectance spectrum confirms a uniform coating of the MC with the polyelectrolyte throughout the entire porous nano‐/mesostructure, as neither broadening nor additional shoulder are appreciable in the reflectance spectrum. [ 34 ] As expected, Fabry–Pérot reflectance fringes dominate the reflectance spectrum of the non‐resonant PSiO 2 reference structure at any processing step (Figure 2b).…”

Porous Silicon-Based Photonic Biosensors: Current Status and Emerging Applications

“…Improvement in sensitivity by substituting the simple PSi Fabry–Pérot interferometer with sophisticated multilayered-optical structures has already been vastly established, and research work in recent years has focused on optimization of these complex structures for improving their sensitivity. ,− Such structures include Bragg mirrors, , rugate filters, ,,− microcavities, ,,,,,− Thue–Morse structures, waveguides, , Vernier effect-based structures, Bloch surface wave structures, ring resonators, , and diffraction gratings . Weiss and co-workers extensively studied biosensors based on DNA-PNA hybridization with different PSi-based optical structures.…”

“…PSi matrices are attractive and versatile scaffolds for the incorporation of polymers and hydrogels. ,− ,− The principle concepts of designing and fabricating PSi/polymer hybrids were recently reviewed by Segal and co-workers . The integrated polymer can provide mechanical and chemical stability to the PSi host and offer new functionalities for molecular recognition and sensing. ,, Moreover, the integration of polymers within nanostructured PSi enables rational device design that can display a combination of controlled chemical and physical characteristics that are not exhibited by either individual component. , These hybrids have been extensively studied for drug delivery applications, − but few studies have reported their use for sensing and biosensing applications. , For example, a design of responsive devices through various mechanisms, ,, the development of dual-mode platforms, and the ability to improve the biosensor sensitivity were reported.…”

“…Throughout this review, various applications have been described, which are also summarized in Table . These include medical diagnostics and disease monitoring using biosensors targeting pathological condition biomarkers, ,, such as protein biomarkers for cancer, hydatid disease, inflammation and sepsis, and wound infection and healing, ,, as well as detection of medically relevant antibodies . Numerous platforms for oligonucleotide detection have been designed, as summarized in Table , including miRNA detection. , Additionally, detection of clinically relevant small molecules, such as insulin and glucose, was also realized. ,,, A promising medical application of immense potential is the evaluation of antibiotic susceptibility.…”

“…Throughout this review, various applications have been described, which are also summarized in Table 1. These include medical diagnostics and disease monitoring using biosensors targeting pathological condition biomarkers, 117,177,178 such as protein biomarkers for cancer, 179 hydatid disease, 129 inflammation and sepsis, 47 and wound infection and healing, 118,181,262 as well as detection of medically relevant antibodies. 180 Numerous platforms for oligonucleotide detection have been designed, as summarized in Table 1, including miRNA detection.…”