Luminescence and sensitivity enhancement of oxygen sensors through tuning the spectral overlap between luminescent dyes and SiO₂@Ag nanoparticles

Abstract

We utilized a seeded growth method to synthesize SiO 2 @Ag NPs with tunable plasmonic resonance peak to investigate the effect of spectral overlap between the SiO 2 @Ag plasmonic resonance spectrum and the PtTFPP-based oxygen sensors' absorbance spectra on luminescence enhancement and performance optimization. An organic silicate was used as the matrix. Oxygen-sensors were produced by directly casting the mixture of NPs and dyes with silicate gels onto glass slides. Oxygen-induced spectral response of the PtTFPP was obtained as the analytical signal. Our results show that when the plasmonic resonance spectrum of SiO 2 @Ag has a maximum wavelength overlap with the absorbance spectra of dyes, the Stern-Volmer slopes were enhanced by almost an order of magnitude. At 21% O 2 , the Stern-Volmer plot achieved a maximum seven-fold increase over the oxygen sensor without the metal-enhanced luminescence. Our results also show that 10% wt NPs is the optimal amount for the PtTFPP-SiO 2 @Ag based oxygen sensors that can eliminate self-quenching and the NRET process.These data confirm that the spectral overlap between the dyes and noble metal NPs and how to eliminate self-quenching and the NRET process are vital to high-sensitive oxygen sensors. We have also shown that our fabrication process of these oxygen sensors is repeatable.

Silica Nanoparticles Coated with Smaller Au Nanoparticles for the Enhancement of Optical Oxygen Sensing

“…These data further support experimental evidence that the intensity of dyes enhanced by the SiO 2 /Au NPs relies strongly on the overlap between the excitation spectra properties of the dye with the LSPR of the NP, which is consistent with our previous findings using the seeded growth of SiO 2 @Ag with tunable plasmon resonances. 18 Compared with that of the PtTFPP-SiO 2 /Ag-based oxygen sensors, the sensitivity of PtTFPP-SiO 2 /Au-based oxygen sensors is slightly lower at low concentrations (0−5%) but almost the same at 5−21% (Figure S2). The difference can be explained as follows: the absorption spectrum of the PtTFPP has a Soret band (S 0 to S 2 transition) at 392 nm and two Q bands (S 0 to S 1 transition) at 508 and 541 nm, respectively.…”

“…The synthesis of SiO 2 nanospheres was performed, as described in our previous publication. 18 4.2. Synthesis of SiO 2 /Au.…”

“…Synthesis of SiO 2 /Au. The synthesis of SiO 2 /Ag described in our previous publication 18 was adjusted for the use of Au. Here, we dispersed 0.6 g of SiO 2 in 60 mL of PEI (1 wt %) solution, and then, the solution was stirred for 4 h. The SiO 2 nanospheres from the previous step were washed three times with water and then placed in 6 mL of water (0.1 g/mL).…”

“…In an ethanol solution, the luminescence intensity-enhanced factor is 3. 18 Our group prepared a series of SiO 2 @Ag with tunable plasmonic resonance and embedded in silica gels containing PtTFPP dyes to measure its variation with respect to oxygen concentration. The SiO 2 @Ag-Pt(II)-doped oxygen sensors exhibit high sensitivity, 7.7 times higher than that of Pt(II)-doped oxygen sensors.…”

“…Optical oxygen sensors based on the quenching of luminescence emitted from dyes have experienced increasing success in the past decades since their introduction to detecting oxygen. , These optical oxygen sensors exhibit several advantages such as unmatched sensitivity, remote sensing capabilities via fiber optics, noninvasiveness, and low toxicity, − which have been successfully used both in scientific and commercial terms. − However, the response of optical oxygen sensors always faces many problems in actuality when the dye displays weak emission intensity to variations of oxygen concentrations . While, in the vicinity of metal nanostructures, plasmon excitation providing enhanced optical fields can greatly enhance the emission intensity. − Metal-enhanced luminescence (MEL) can not only provide enhanced emissions but also expand the field of dyes by incorporating weak quantum emitters, which has been proved to be an efficient method to increase luminescence sensitivity and intensity in optical oxygen sensors. − Chu’s group fabricated a metal-enhanced optical oxygen sensor. This sensor comprises an optical fiber that was coated at one end with platinum­(II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) and silver-coated silica nanoparticles (NPs) in an n-octyltriethoxysilane (octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel .…”