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The development of novel molecular sieves opens opportunities in the development of more sensitive analytical devices. In this paper, metal organic frameworks (MOFs), specifically ZIF-8 and ZIF-93, are grown on fiber optic based surface plasmon resonance (FO-SPR) sensors. FO-SPR has enabled sensitive sensing capabilities in biomedical settings and the addition of an MOF coating opens the way for the sensing of volatile organic compounds (VOCs) in gaseous media. FO-SPR probes were homogeneously functionalized with ZIF-8 and ZIF-93 in each case using two different precursor solutions to obtain a sequential nucleation and growth phase. The difference in MOF nucleation and growth kinetics of the two solutions was directly monitored by the FO-SPR system. The two established MOF-FO-SPR sensors were then subjected to sensing experiments with several alcohol vapors to establish their sensing capabilities. Vapors with mPa partial pressures, ppm concentrations, could successfully be detected, e.g., an LOD of 2.5 ppm for methanol detection was acquired. The difference in recognition behavior of the hydrophobic ZIF-8 and more hydrophilic ZIF-93 recognition layers can be exploited to yield qualitative information regarding the vapor composition.

Photocatalytic reactions occur at the crystal-solution interface, and hence specific crystal facet expression and surface defects can play an important role. Here we investigate the structure-related photoreduction at zinc oxide (ZnO) microparticles via integrated light and electron microscopy in combination with silver metal photodeposition. This enables a direct visualization of the photoreduction activity at specific crystallographic features. It is found that silver nanoparticle photodeposition on dumbbell-shaped crystals mainly takes place at the edges of O-terminated (0001̅) polar facets. In contrast, on ZnO microrods photodeposition is more homogeneously distributed with an increased activity at {101̅1̅} facets. Additional time-resolved measurements reveal a direct spatial link between the enhanced photoactivity and increased charge carrier lifetimes. These findings contradict previous observations based on indirect, bulk-scale experiments, assigning the highest photocatalytic activity to polar facets. The presented research demonstrates the need for advanced microscopy techniques to directly probe the location of photocatalytic activity. ispartof: JOURNAL OF PHYSICAL CHEMISTRY LETTERS vol:8 issue:2 pages:340-346 ispartof: location:United States status: published

A home-built fiber optic surface plasmon resonance platform (FO-SPR) was applied to directly screen PCR amplified DNA for mutations. The FO-SPR sensor was used for real-time monitoring of DNA duplex melting during high resolution temperature cycling. The signal of the DNA melting was enhanced by means of gold nanoparticle labels. This FO-SPR genetic assay allowed for detection of single-point mutations (SNP) in less than 20 min. The concept was demonstrated for the analysis of 9 different serogroups of the bacterium Legionella pneumophila, a common human pathogen responsible for atypical pneumonia. FO-SPR allowed us to detect genetic mutations inhibiting PCR, which could lead to amplification bias when molecular diagnostics are applied for L. pneumophila detection. All serogroups were found to display unique melting temperatures, indicating that mutations have accumulated in the target sequence. In a next step, clinical samples of L. pneumophila were analyzed using the FO-SPR sensor. This technology was proven to be reliable for the detection of mutations for those samples that previously displayed ambiguous qPCR quantification results. When these results were benchmarked, FO-SPR results were found to be consistent with Sanger sequencing but not with fluorescence based DNA melting. The presented results convincingly advocate the advantages of FO-SPR as a high resolution and fast genetic screening tool that can compete with the current standard techniques for SNP detection.