Biexciton-like Auger Blinking in Strongly Confined CsPbBr Perovskite Quantum Dots.

Perovskite quantum dots (QDs) with high room-temperature luminescence efficiency have been applied in single-photon sources. While the optical properties of large, weakly confined perovskite nanocrystals have been extensively explored at the single-particle level, few studies have focused on single-perovskite QDs with strong quantum confinement. This is mainly due to their poor surface chemical stability.

Amine Functionalization of Silica Sol-Gel Thin Films via Kinetic Doping: A Novel, Green Approach.

Amine-functionalized thin films are highly desirable technologies for analytical, material, and biochemistry applications. Current functionalization procedures can be costly, environmentally unfriendly, and require many synthetic steps. Here, we present an inexpensive and facile way to functionalize a silica thin film with a 25 000 MW branched polyethylenimine (BPEI), consistent with green chemistry principles.

Multienzyme, Multistep Biosensor Produced through Kinetic Doping.

The recently developed kinetic doping technique has shown promise in loading individual enzymes for use as a biosensor. In this study, the first example of kinetic doping to produce a biosensor loaded with more than one enzyme and using a multistep reaction pathway for detection is presented. Glucose oxidase (GOD) is shown to load both individually and together with horseradish peroxidase (HRP) with the tandem action of the two enzymes proving to be effective at detecting glucose in solution.

Kinetically Doped Silica Sol-Gel Optical Biosensors: Expanding Potential Through Dip-Coating.

Kinetic doping has previously been shown to be an effective method of doping silica sol-gel thin films with an enzyme to construct biosensors. Until now, kinetic doping has only been applied to films produced through the spin-coating method. In this study, we present the use of dip-coating to produce thin films kinetically doped for biosensor development.

Silica Sol-Gel Optical Biosensors: Ultrahigh Enzyme Loading Capacity on Thin Films via Kinetic Doping.

Easy to use and easy to produce biosensors would have a huge range of applications. To reach this goal many see the incorporation of a protein into a sol-gel network as one of the most viable options. The current most prevalent technique of predoping presents inherent limits on the concentration possible for the resulting thin film.

Kinetic approach to hyper-doped optical quality thin films.

Efficient and benign doping of thin films is key for materials applications and sensor development. Herein, an alternative method of doping is presented where R6G is loaded to an evolving silica thin film. Dopant loading is markedly enhanced and doping can be carried out under relatively benign conditions.

Energy-dependent motion of TonB in the Gram-negative bacterial inner membrane.

Gram-negative bacteria acquire iron with TonB-dependent uptake systems. The TonB-ExbBD inner membrane complex is hypothesized to transfer energy to outer membrane (OM) iron transporters. Fluorescence microscopic characterization of green fluorescent protein (GFP)-TonB hybrid proteins revealed an unexpected, restricted localization of TonB in the cell envelope.

Fluorescence-on response via CB7 binding to viologen-dye pseudorotaxanes.

Fluorescence-on sensors typically rely on disrupting photoinduced electron transfer quenching of the excited state through binding the electron donor. To provide a more general fluorescence-on signaling unit, a quencher-fluorophore dyad has been developed in which quenching by electron transfer to a tethered viologen acceptor can be disrupted through complexation of the viologen by cucurbit[7]uril (CB7). Dyads of benzyl viologen-rhodamine B or a BODIPY fluorophore gave upon CB7 complexation 14- and 30-fold fluorescence enhancement, respectively.

Cucurbit[7]uril disrupts aggregate formation between rhodamine B dyes covalently attached to glass substrates.

Dye aggregation is detrimental to the performance of high optical density dye-doped photonic materials. To overcome this challenge, the ability of cucurbit[7]uril (CB7) as a molecular host to disrupt aggregate formation on glass substrates was examined. Rhodamine B was covalently attached to glass slides by initially coating the surface with azidohexylsiloxane followed by copper-catalyzed "click" triazole formation with rhodamine B propargyl ester.

Balance between Coulombic interactions and physical confinement in silica hydrogel encapsulation.

We examined the behavior of various entrapped guest molecules within silica hydrogel and evaluated the effect of Coulombic interactions and physical confinement on molecular mobility. Although rhodamine 6G (R6G) and fluorescein (FL) share similar size and molecular structure, their behavior in silica hydrogel was found to be dramatically different. A good majority of R6G was immobilized with little to no exchangeable molecules, whereas FL displayed a considerable amount of mobility in silica hydrogel.

Comparative study of guest charge-charge interactions within silica sol-gel.

We investigated the effect of charge-charge interactions on the mobilities of rhodamine 6G (R6G), Nile Red, sulforhodamine B, and Oregon Green 514 (ORG) guest molecules within a silica sol-gel host as the guest charge progressed from positive to neutral to negative. Through classification of the mobility as fixed, tumbling, or intermediate behavior, we were able to distinguish differences in surface attraction as the guest charge was varied. On the basis of our results, an attractive charge (as tested by cationic R6G) does not contribute significantly to mobility within dry films.

Liposomes as protective capsules for active silica sol-gel biocomposite synthesis.

Using liposome to shield an enzyme from hostile chemical environments during the sol-gel formation process has resulted in a novel approach to synthesizing silica sol-gel biocomposite materials. By reporting the encapsulation of horseradish peroxidase and firefly luciferase, we demonstrate that this new protocol can produce silica biocomposites that are more active than trapping the enzymes directly into hydrogels.

Coulombic interactions on the deposition and rotational mobility distributions of dyes in polyelectrolyte multilayer thin films.

We employed negatively charged fluorescein (FL), positively charged rhodamine 6G (R6G), and neutral Nile Red (NR) as molecular probes to investigate the influence of Coulombic interaction on their deposition into and rotational mobility inside polyelectrolyte multilayer (PEM) films. The entrapment efficiency of the dyes reveals that while Coulombic repulsion has little effect on dye deposition, Coulombic attraction can dramatically enhance the loading efficiency of dyes into a PEM film. By monitoring the emission polarization of single dye molecules in polyethylenimine (PEI) films, the percentages of mobile R6G, NR, and FL were determined to be 87 +/- 4%, 76 +/- 5%, and 68 +/- 3%, respectively.

Probing the dynamic guest-host interactions in sol-gel films using single molecule spectroscopy.

Organic dyes usually exhibit enhanced photostability when trapped inside sol-gel silicates. The enhanced photostability is attributed to the reduction of intramolecular motions that facilitate photodegradation. We report the simultaneous detection of mobility and photostability of sol-gel encapsulated didodecyl-3,3,3',3'-tetramethylindocarbocyanine (DiI) using single molecule spectroscopy.