Toward Real-Time Monitoring and Control of Single Nanoparticle Properties with a Microbubble Resonator Spectrometer.

Optical microresonators have widespread application at the frontiers of nanophotonic technology, driven by their ability to confine light to the nanoscale and enhance light-matter interactions. Microresonators form the heart of a recently developed method for single-particle photothermal absorption spectroscopy, whereby the microresonators act as microscale thermometers to detect the heat dissipated by optically pumped, nonluminescent nanoscopic targets. However, translation of this technology to chemically dynamic systems requires a platform that is mechanically stable, solution compatible, and visibly transparent.

Single-particle photothermal imaging via inverted excitation through high-Q all-glass toroidal microresonators.

Whispering-gallery mode (WGM) microresonators have recently been employed as platforms for label-free single-molecule and single-particle detection, imaging, and spectroscopy. However, innovations in device geometry and integration are needed to make WGM microresonators more versatile for biological and chemical applications. Particularly, thick device substrates, originating from wafer-scale fabrication processing, prevent convenient optical interrogation.

Exploring Electronic Structure and Order in Polymers via Single-Particle Microresonator Spectroscopy.

PSS, a transparent electrically conductive polymer, finds widespread use in electronic devices. While empirical efforts have increased conductivity, a detailed understanding of the coupled electronic and morphological landscapes in PEDOT:PSS has lagged due to substantial structural heterogeneity on multiple length-scales. We use an optical microresonator-based absorption spectrometer to perform single-particle measurements, providing a bottom-up examination of electronic structure and morphology ranging from single PEDOT:PSS polymers to nascent films.

Sculpting Fano Resonances To Control Photonic-Plasmonic Hybridization.

Hybrid photonic-plasmonic systems have tremendous potential as versatile platforms for the study and control of nanoscale light-matter interactions since their respective components have either high-quality factors or low mode volumes. Individual metallic nanoparticles deposited on optical microresonators provide an excellent example where ultrahigh-quality optical whispering-gallery modes can be combined with nanoscopic plasmonic mode volumes to maximize the system's photonic performance. Such optimization, however, is difficult in practice because of the inability to easily measure and tune critical system parameters.

Optical Microresonators for Sensing and Transduction: A Materials Perspective.

Optical microresonators confine light to a particular microscale trajectory, are exquisitely sensitive to their microenvironment, and offer convenient readout of their optical properties. Taken together, this is an immensely attractive combination that makes optical microresonators highly effective as sensors and transducers. Meanwhile, advances in material science, fabrication techniques, and photonic sensing strategies endow optical microresonators with new functionalities, unique transduction mechanisms, and in some cases, unparalleled sensitivities.

Suppression of Kasha's rule as a mechanism for fluorescent molecular rotors and aggregation-induced emission.

Although there are some proposed explanations for aggregation-induced emission, a phenomenon with applications that range from biosensors to organic light-emitting diodes, current understanding of the quantum-mechanical origin of this photophysical behaviour is limited. To address this issue, we assessed the emission properties of a series of BF-hydrazone-based dyes as a function of solvent viscosity. These molecules turned out to be highly efficient fluorescent molecular rotors.

Correction: Dynamic ruffling distortion of the heme substrate in non-canonical heme oxygenase enzymes.

Correction for 'Dynamic ruffling distortion of the heme substrate in non-canonical heme oxygenase enzymes' by Amanda B. Graves et al., Dalton Trans.

Dynamic ruffling distortion of the heme substrate in non-canonical heme oxygenase enzymes.

Recent work by several groups has established that MhuD, IsdG, and IsdI are non-canonical heme oxygenases that induce significant out-of-plane ruffling distortions of their heme substrates enroute to mycobilin or staphylobilin formation. However, clear explanations for the observations of "nested" S = ½ VTVH MCD saturation magnetization curves at cryogenic temperatures, and exchange broadened (1)H NMR resonances at physiologically-relevant temperatures have remained elusive. Here, MCD and NMR data have been acquired for F23A and F23W MhuD-heme-CN, in addition to MCD data for IsdI-heme-CN, in order to complete assembly of a library of spectroscopic data for cyanide-inhibited ferric heme with a wide range of ruffling deformations.

Chip-Scale Fabrication of High-Q All-Glass Toroidal Microresonators for Single-Particle Label-Free Imaging.

Whispering-gallery-mode microresonators enable materials for single-molecule label-free detection and imaging because of their high sensitivity to their micro-environment. However, fabrication and materials challenges prevent scalability and limit functionality. All-glass on-chip microresonators significantly reduce these difficulties.