Photonic Crystal Aqueous Metal Cation Sensing Materials

Abstract

We developed a polymerized crystalline colloidal array photonic material that senses metal cations in water at low concentrations (PCCACS). Metal cations such as Cu2+, Co2+, Ni2+, and Zn2+ bind to 8-hydroxyquinoline groups covalently attached to the PCCACS. At low metal concentrations (<microM), the cations form bisliganded complexes with two 8-hydroxyquinolines that cross-link the hydrogel and cause it to shrink, which blue shifts the photonic crystal diffraction. These bisliganded cross-links break at higher cation concentrations due to the formation of monoliganded cation complexes. This red shifts the diffraction. We have extended hydrogel volume phase transition theory in order to quantitatively model the diffraction dependence upon metal concentration. These materials can be used as a dosimeter to sense extremely low metal cation concentrations or as a sensor material for concentrations greater than 1 microM. Metal cation concentrations can be determined visually from the color of the diffracted light or can be determined by reflectance measurements using a spectrophotometer. This sensing material could be used in the field to visually determine metal cation concentrations in drinking water. A color chart would be used to relate the diffracted color to the metal cation concentration.

Soft Nanotechnology with Soft Nanoparticles

“…These systems have also been used for detecting various analytes, where the polymer that connects the particles is responsive to the analyte and, in the presence of that analyte, causes a change in lattice spacing. [220] In one example boronic acid groups were incorporated into the crystalline array for glucose-sensing applications. [221] ####Another example of polymerized colloidal crystal assembly was reported by Hu et al [74] They synthesized two types of pNIPAm microgels, one had acrylic acid units and the other had 2-hydroxyethyl acrylate units.…”

Materials Aspects of Photonic Crystals

“…[176] The same principle can be used to sense carbohydrates, [177] redox state, [178] pH, or ionic strength. [179] Hydrogel-encapsulated colloidal crystals can also find applications as mechanochromic PCs.…”

Responsive photonische Kristalle

“…[112,126] Momentan haben Ionensensoren noch den Nachteil, dass zwei oder drei fremde Ionenarten die Detektion stören, z. B. beeinträchtigen Ba Wie schon erwähnt, sind hohe Ionenstärken ein großes Problem für die Detektion hoher Ionenkonzentrationen, da ein Anstieg der Ionenstärke den osmotischen Druck in der Matrix verringert.…”