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1. Ultrafast photoinduced energy and charge transfer: concluding remarks

   https://doi.org/10.1039/c9fd90030f  

   Kohler, Bern (July 2019, Faraday Discussions)

   The ability to characterize and control the energy and charge transfer events triggered by the photoexcitation of molecules and materials is of fundamental importance to many fields, including the sustainable capture and conversion of solar energy. This article summarizes the papers that were presented and discussed at the recent Faraday discussion meeting on ultrafast photoinduced energy and charge transfer. Ultrafast laser spectroscopy and theory were at the center of discussions on photoinduced phenomena in biological and nanoscale systems of interacting absorbers. Many of the questions that motivate this field of science have occupied scientists for many decades, as a look back to a Faraday discussion meeting that took place 60 years earlier reveals. 

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2. Quantum effects in complex systems: summarizing remarks

   https://doi.org/10.1039/c9fd00097f  

   Hammes-Schiffer, Sharon (January 2020, Faraday Discussions)

   Quantum mechanical phenomena such as coherence, spin dynamics, and tunneling have been observed in biological, electrochemical, polymeric, and many other condensed phase processes. This paper summarizes the diverse contributions to the Faraday Discussion on quantum effects in complex systems. Various processes exhibiting quantum mechanical behavior were examined using advanced spectroscopic and theoretical methods. An emerging theme was the critical importance of feedback between experiment and theory, particularly in the form of experimental testing of theoretical predictions. 

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3. Defect Characterization, Imaging, and Control in Wide Band Gap Semiconductors and Devices

   https://doi.org/10:1007/s11664-018-6214-9  

   L.J. Brillson, G.M. Foster (January 2018, Journal of electronic materials)

   Wide-bandgap semiconductors are now leading the way to new physical phenomena and device applications at nanoscale dimensions. The impact of defects on the electronic properties of these materials increases as their size decreases, motivating new techniques to characterize and begin to control these electronic states. Leading these advances have been the semiconductors ZnO, GaN, and related materials. This paper highlights the importance of native point defects in these semiconductors and describes how a complement of spatially localized surface science and spectroscopy techniques in three dimensions can characterize, image, and begin to control these electronic states at the nanoscale. A combination of characterization techniques including depth-resolved cathodoluminescence spectroscopy, surface photovoltage spectroscopy, and hyperspectral imaging can describe the nature and distribution of defects at interfaces at both bulk and nanoscale surfaces, their metal interfaces, and inside nanostructures themselves. These features as well as temperature and mechanical strain inside wide-bandgap device structures at the nanoscale can be measured even while these devices are operating. These advanced capabilities enable several new directions for describing defects at the nanoscale, showing how they contribute to device degradation, and guiding growth processes to control them. 

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4. A microfluidic electrochemical flow cell capable of rapid on-chip dilution for fast-scan cyclic voltammetry electrode calibration

   https://doi.org/10.1007/s00216-020-02493-z  

   Delong, Lauren M.; Li, Yuxin; Lim, Gary N.; Wairegi, Salmika G.; Ross, Ashley E. (February 2020, Analytical and Bioanalytical Chemistry)

   Here, we developed a microfluidic electrochemical flow cell for fast-scan cyclic voltammetry which is capable of rapid on-chip dilution for efficient and cost-effective electrode calibration. Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes is a robust electroanalytical technique used to measure subsecond changes in neurotransmitter concentration over time.Traditional methods of electrode calibration for FSCV require several milliliters of a standard. Additionally, generating calibration curves can be time-consuming because separate solutions must be prepared for each concentration. Microfluidic electrochemical flow cells have been developed in the past; however, they often require incorporating the electrode in the device, making it difficult to remove for testing in biological tissues. Likewise, current microfluidic electrochemical flow cells are not capable of rapid on-chip dilution to eliminate the requirement of making multiple solutions. We designed a T-channel device, with microchannel dimensions of 100 μm × 50 μm, that delivered a standard to a 2-mm-diameter open electrode sampling well. A waste channel with the same dimensions was designed perpendicular to the well to flush and remove the standard. The dimensions of the T-microchannels and flow rates were chosen to facilitate complete mixing in the delivery channel prior to reaching the electrode. The degree of mixing was computationally modeled using COMSOL and was quantitatively assessed in the device using both colored dyes and electrochemical detection. On-chip electrode calibration for dopamine with FSCV was not significantly different than the traditional calibration method demonstrating its utility for FSCV calibration. Overall, this device improves the efficiency and ease of electrode calibration. 

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5. In operando optical characterization of organic mixed ionic–electronic conductors for unraveling charge transport and doping dynamics—A perspective

   https://doi.org/10.1063/5.0274369  

   Chen, Linqi; Ma, Yingying; Guo, Peijun (July 2025, The Journal of Chemical Physics)

   Organic mixed ionic–electronic conductors (OMIECs) are a unique class of soft, conjugated polymeric materials. The simultaneous electronic and ionic transport of OMIECs enables a new type of device, namely, organic electrochemical transistors, among other emerging technologies. However, the dynamic nature—where charge transport, doping kinetics, and morphological changes occur concurrently—poses significant challenges in the characterization and understanding of OMIECs. Recent advances in in situ optical techniques, including ultraviolet–visible–near-infrared spectroscopy, Raman spectroscopy, and microscopy imaging, have provided valuable insights into the charge transport mechanisms and ionic doping dynamics spanning from the microscopic to the device scale. In this perspective, based on several archetypal OMIECs, we survey how spectroscopic signatures were used to reveal key physical processes in these materials. Looking forward, we propose that ultrafast spectroscopy and microscopy techniques—such as transient absorption spectroscopy, terahertz time-domain spectroscopy, pump–probe microscopy, and photothermal microscopy—hold great potential for uncovering more fundamental mechanisms of OMIEC operation, including quasiparticle dynamics, intrinsic electrical conductivity, and carrier mobility, which remain under-explored. Integrating optical characterization with electrochemical measurements will enable in operando studies on state-of-the-art devices, with results further refined by parallel advancements in theoretical modeling. Altogether, we envision in operando optical characterization with spatial, spectral, and temporal resolution across multiple scales as a powerful pathway to advance the understanding of OMIEC mechanisms and their structure–property relationships. 

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