Photostable phosphorescent polymer nanospheres for high sensitivity detection

Abstract

Time-gated interrogation of phosphorescent labels allows high sensitivity detection of analytes by excluding background fluorescence and stray excitation light. Here we report a method for preparing phosphorescent polymer nanospheres with optical properties specifically designed to enable time-gated detection with both organic and inorganic light-emitting diodes and photodiodes. The nanospheres were formed by co-precipitating the phosphorescent dye ruthenium diphenyl phenanthroline with the amphiphilic statistical co-polymer poly(styrene-co-maleic acid). To minimize aggregation and ensure effective encapsulation against water and oxygen ingress, the polymer chains were cross-linked with the small-molecule crosslinker bisphenol A diglycidyl ether, resulting in near-monodisperse nanospheres with excellent resilience against aggregation and quenching. The nanospheres exhibited long phosphorescence lifetimes of 5.3 AE 0.1 ms, high photoluminescence quantum efficiencies of 33 AE 5%, and excellent stability under UV irradiation. Using a blue light-emitting diode as a light-source and a silicon photodiode as a detector, a low detection limit of 4 mg ml À1 was achieved. The suitability of the nanospheres for bioanalysis was demonstrated by surface functionalising them with biotin to yield a simple biolabel for streptavidin.

Versatile design and synthesis of nano-barcodes

“…Despite these benefits, the process offers very little control because of the 193 (b) RAFT polymerization of Fe 3 O 4 @poly(methacrylic acid). 189 (c) Co-precipitation of the encoding element and the polymer to form the barcodes, 196 and (d) Solvothermal method to prepare differently shaped barcodes based on different ratios of Ag + PVP dispersed in DMF solvent. 199 (e) Sol-gel method to prepare QD encoded SiO 2 beads.…”

“…In this strategy, encoding elements are co-precipitated with polymers to form encoded nanospheres. [196][197][198] Lipophilic encoding elements and amphiphilic polymers (insoluble in a water-organic solvent mixture) are co-dissolved in a small amount of organic solvent miscible in water (Fig. 14c).…”

Functionalized phosphorescent nanoparticles in (bio)chemical sensing and imaging – A review

“…The use of polymers for encapsulation of phosphorescent dyes is particularly advantageous for bioimaging, since the size of the nanospheres can be tuned by controlling the polymer chain length, while inclusion of appropriate functional groups can be used to tailor the nanosphere surface to provide biocompatibility or to attach bioactive molecules [38].…”

“…Subsequent crosslinking of the polymer chains provides high quantum efficiencies and better photostability to equivalent noncrosslinked nanospheres due to a better protection of the phosphors against oxygen and other emission quenchers [41]. Recently, the use of small-molecule crosslinking agents, such as bisphenol A diglycidyl ether (BPA) in conjunction with a single amphiphilic polymer, has been proposed as an alternative to the use of multiple polymers with crossreactive functional groups, achieving a better control over the size, morphology and surface chemistry of the nanospheres [38] as shown on Figure 4.…”

“…By using a pulsed excitation source and measuring the phosphorescence emission after a "delay time", it is possible to eliminate any contribution that comes from the excitation source or from the fluorescent background. Therefore, phosphorescence-based methodologies are an excellent option to develop analytical strategies in biological media where scattering macromolecules and luminescent species abound [38]. Detection of glucose was also performed based on quenching of the phosphorescence.…”