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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Online Monitoring of Cell Growth on PDMS-PDMS Reversible Microfluidic Bioreactor Integrated to Optical Fiber Sensor
摘要： A microfluidic bioreactor was fabricated by curing PDMS over 3D-printed molds, and it contains microchannels and perfusion chambers instrumented with optical fibers for the online analysis of the cellular growth. The channels were designed for allowing both the complete mixture of reagents and the possibility of generation of concentration gradients, and the perfusion chambers are isolated from them by polycarbonate membranes, providing a chemical environment with a constant concentration of nutrients for the cells. The optical fibers are laterally inserted in the chambers, and the monitoring of cells concentration is based on the quasi-elastic light scattering: as the total number of cells grows, there is an increase on the dispersion of the reflected intensity data, and the autocorrelation of the values allows the inference of the concentration. The sensor signals obtained during the fermentation of S. cerevisiae were equivalent to the cell counting on the Neubauer chamber using an optical microscope, leading to a value of the maximum specific growth rate μm of 0.50 h-1. This optical monitoring system has proven to be easily manufacturable and capable of performing fast screening and online monitoring of the microbial kinetics.
关键词： microbial kinetics,online monitoring,optical fiber sensor,quasi-elastic light scattering,Microfluidic bioreactor
更新于2025-09-12 10:27:22
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Toward Highly Thermal Stable Perovskite Solar Cells by Rational Design of Interfacial Layer
摘要： Heat is crucial to the long term stability of perovskite solar cells (PVSCs). Herein, thermal stability of PVSCs based on metal oxide (MO) and polymer (P) was investigated. Firstly, chemical decomposition behavior of perovskite films was characterized and analyzed, revealing that chemically active MO would accelerate the decomposition of methylamine lead iodide (MAPbI3). Secondly, thermal-induced stress, resulting from the mismatched thermal expansion coefficients of different layers of PVSCs, and its effect on the mechanical stability of perovskite films were studied. Combining experiment and simulation, we conclude that “soft” (low modulus) and thick (> 20 nm) interfacial layers offer better relaxation of thermal-induced stress. As a result, PVSCs employing thick polymer interfacial layer offer a remarkably improved thermal stability. This work offers not only the degradation insight of perovskite films on different substrates, but also the path toward highly thermal stable PVSCs by rational design of interfacial layers.
关键词： perovskite solar cells,mechanics simulation,interfacial layer,heat endurance,kinetics analysis
更新于2025-09-12 10:27:22
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Effect of metal ion solubility on the oxidative assembly of metal sulfide quantum dots
摘要： The versatility of the oxidative assembly method for the creation of 2D and 3D quantum dot (QD) architectures represents both an opportunity and a challenge as a method enabling controlled placement of chemically distinct QDs in multicomponent systems. The opportunity lies in the ability to independently tune the kinetics of the different components so that they are similar (leading to well-mixed systems) or different (enabling gradient or phase-segregated composites) using a wide range of variables; the challenge lies in understanding those variables and how their interplay affects the overall kinetics. Here, we show that the identity of the cation in the sulfide matrix (M = Cd2+ vs Zn2+) plays a large role in the kinetics of assembly of mass spectrometry QDs, attributed to differences in solubility. Time resolved dynamic light scattering is used to monitor the hydrodynamic radius, Rh. ZnS shows an exponential growth associated with reaction-limited cluster aggregation (RLCA), whereas CdS demonstrates a significant induction period (10–75 min) followed by a growth step that cannot be distinguished between RLCA and diffusion limited cluster aggregation. These data correlate with relative solubilities of the nanoparticles, as probed by free-cation concentration. Data also confirm prior studies showing that cubic-closest-packed (ccp) lattices are kinetically slow relative to hexagonally closest-packed (hcp); using the slope of the ln Rh vs time plot for the rate constant, the values of 0.510 s?1 and 3.92 s?1 are obtained for ccp ZnS and hcp ZnS, respectively. Thus, both the structure and the solubility are effective levers for adjusting the relative reactivity of QDs toward oxidative assembly.
关键词： kinetics,solubility,quantum dots,dynamic light scattering,oxidative assembly
更新于2025-09-12 10:27:22
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Acetate based Crystallization Kinetics Modulation of CsPbI2Br for Improved Photovoltaic Performance
摘要： Inorganic CsPbI2Br perovskite has emerged to be a promising candidate for photovoltaic materials, while developing additives engineering strategies to address the issues of defects induced crystalline phase transformation from photoactive perovskite phase to non-perovskite phase has been a challenge to achieve their outstanding optoelectronic properties and thermal stability. In this work, we demonstrate an effective acetate mediation strategy for significantly retarding the crystallization process and thus the phase transformation, which leads to much improved optoelectronic performance of the solar cells. It was demonstrated that the addition of acetate like Cobalt(II) acetate (Co(Ac)2) or zinc acetate (Zn(Ac)2) could lead to significantly retarded crystallization process of perovskite films, as well as the formation of the flat, dense and defect-less perovskite film. We propose that the perovskite crystal grows up following the ostwald ripening mechanism at 270 ℃ annealing temperature, during which the acetate in the perovskite film would be squeezed from boundaries by grains growing cause the acetate cannot through the crystalline. Based on the proposed strategy of crystallization kinetics modulation with acetate, the photon conversion efficiency (PCE) of champion device with that acetate modified perovskite film can reach as high as 15.04%, and superb fill factor of 80.46%. We thus believe that our work could provide an effective alternative for the designing of high performance inorganic CsPbI2Br perovskite solar cells.
关键词： Acetate,CsPbI2Br,All-inorganic perovskite solar cell,Photo-conversion efficiency,Crystallization kinetics
更新于2025-09-12 10:27:22
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Electron Transfer Kinetics at Graphene Quantum Dot Assembly Electrodes
摘要： Electrochemical performance of nanostructured carbon electrodes was evaluated using cyclic voltammetry and a simple simulation model. The electrodes were prepared from soluble precursors by anodic electrodeposition of two sizes of graphene quantum dot assemblies (HBC and CQD) onto conductive support. Experimental and simulated voltammograms enabled the extraction of the following electrode parameters: conductivity of the electrodes (a combination of ionic and electronic contributions), density of available electrodes states at different potentials and tunneling rate constant (Marcus-Gerischer model) for interfacial charge transfer to ferrocene/ferrocenium (Fc/Fc+) couple. The parameters indicate that HBC and CQD have significant density of electronic states at potentials more positive than –0.5 V vs Ag/Ag+. Enabled by these large densities, the electron transfer rates at the Fc/Fc+ thermodynamic potential are several orders of magnitude slower than those commonly observed on other carbon electrodes. This study is expected to accelerate the discovery of improved synthetic carbon electrodes by providing fast screening methodology of their electrochemical behavior.
关键词： cyclic voltammetry,kinetics,interface,electrode,electron transfer,graphene quantum dots
更新于2025-09-12 10:27:22
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Propagation Kinetics of Isoprene Radical Homopolymerization Derived from Pulsed Laser Initiated Polymerizations
摘要： The propagation kinetics of isoprene radical polymerizations in bulk and in solution are investigated via pulsed laser initiated polymerizations and subsequent polymer analyses via size-exclusion chromatography, the PLP-SEC method. Because of low polymerization rate and high volatility of isoprene, the polymerizations are carried out at elevated pressure ranging from 134 to 1320 bar. The temperatures are varied between 55 and 105 °C. PLP-SEC yields activation parameters of kp (Arrhenius parameters and activation volume) over a wide temperature and pressure range that allow for the calculation of kp at technically relevant ambient pressure conditions. The kp values determined are very low, e.g., 99 L mol?1 s?1 at 50 °C, which is even lower than the corresponding value for styrene polymerizations. The presence of a polar solvent results in a slight increase of kp compared to the bulk system. The kp values reported are important for determining rate coefficients of other elemental reactions from coupled parameters as well as for modeling isoprene free-radical polymerizations and reversible deactivation radical polymerization with respect to tailored polymer properties and optimizing the polymerization processes.
关键词： polyisoprene,radical polymerization,kinetics,pulsed laser initiated polymerization
更新于2025-09-11 14:15:04
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A Plasmonic Approach to Study Protein Interaction Kinetics through the Dimerization of Functionalized Ag Nanoparticles
摘要： Understanding the kinetics of protein interactions plays a key role in biology with significant implications for the design of analytical methods for disease monitoring and diagnosis in medical care, research and industrial applications. Herein, we introduce a novel plasmonic approach to study the binding kinetics of protein-ligand interactions following the formation of silver nanoparticles (Ag nps) dimers by UV-Vis spectroscopy that can be used as probes for antigen detection and quantification. to illustrate and test the method, the kinetics of the prototype biotin-streptavidin (Biot-StV) pair interaction was studied. controlled aggregates (dimers) of StV functionalized Ag nps were produced by adding stoichiometric quantities of gliadin-specific biotinylated antibodies (IgG-Biot). The dimerization kinetics was studied in a systematic way as a function of Ag NPs size and at different concentrations of IgG-Biot. The kinetics data have shown to be consistent with a complex reaction mechanism in which only the Ag NPs attached to the IgG-Biot located in a specific STV site are able to form dimers. These results help in elucidating a complex reaction mechanism involved in the dimerization kinetics of functionalized Ag nps, which can serve as probes in surface plasmon resonance-based bioassays for the detection and quantification of different biomarkers or analytes of interest.
关键词： biotin-streptavidin interaction,silver nanoparticles,dimerization,protein interaction kinetics,plasmonic approach,surface plasmon resonance,UV-Vis spectroscopy
更新于2025-09-11 14:15:04
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State-to-state chemical kinetic mechanism for HF chemical lasers
摘要： State-to-state rotational relaxation processes play a critical role in predicting rotational nonequilibrium, which can significantly affect total laser power and spectral distribution. In this paper, the state-to-state rotational relaxation rate coefficients for the pumping reaction of F + H2, the rotational energy transfer processes of HF(υ, j = 0–10) + HF(υ(cid:3), j(cid:3) = 0–10) and HF(υ, j = 0–10) + H2 are calculated. Subsequently, a detailed state-to-state chemical kinetic mechanism is constructed including 61 species and 124,482 elementary reactions for HF chemical lasers. All of these rotational relaxation rate coefficients have been expressed with Arrhenius-like formulas. A comparison of the Boltzmann distribution model with the detailed state-to-state chemical mechanism has been analysed and discussed. These results show that rotational nonequilibrium processes can significantly affect the distribution of ro-vibrational excited HF molecules. The rotational distributions of HF(υ = 0–2, j) are far from equilibrium distribution. Conversely, the distributions of HF(υ = 3, 4, j) seem to be a Boltzmann distribution. These results indicate that numerical models must include the rotational nonequilibrium processes and numerical models using a Boltzmann distribution for the rotational populations cannot predict performance of real HF chemical lasers.
关键词： chemical kinetics,chemical lasers,rotational nonequilibrium,State-to-state model
更新于2025-09-11 14:15:04
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Flower-like gold nanoparticles for enhanced photothermal anticancer therapy by the delivery of pooled siRNA to inhibit heat shock stress response
摘要： Reported reaction kinetics of metal nanoparticles in natural and engineered systems commonly have used proxy measurements to infer chemical transformations, but extension of these methods to complex media has proven difficult. Here, we compare the sulfidation rate of AgNPs using two ion selective electrode (ISE)-based methods, which rely on either (i) direct measurement of free sulfide, or (ii) monitor the free Ag+ available in solution over time in the presence of sulfide species. Most experiments were carried out in moderately hard reconstituted water at pH 7 containing fulvic acid or humic acid, which represented a broad set of known interferences in ISE. Distinct differences in the measured rates were observed between the two proxy-based methods and details of the divergent results are discussed. The two ISE based methods were then compared to direct monitoring of AgNP chemical conversion to Ag2S using synchrotron-based in situ X-ray diffraction (XRD). Using XRD, distinct rates from both ISE-based technique were observed, which demonstrated that ISE measurements alone are inadequate to discriminate both the rate and extent of AgNP sulfidation. XRD rate data elucidated previously unidentified reaction regimes that were associated with AgNP coating (PVP and citrate acid) and NOM components, which provided new mechanistic insight into metallic NP processing. In general, the extent of Ag2S formation was inversely proportional to surface coverage of the initial AgNP. Overall, methods to determine reaction kinetics of nanomaterials in increasingly complex media and heterogeneous size distributions to improve NP-based design and performance will require similar approaches.
关键词： ion selective electrode,X-ray diffraction,natural organic matter,silver nanoparticles,sulfidation kinetics
更新于2025-09-11 14:15:04
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Preparation and Characterization of Water-soluble ZnSe: Fe/ZnSe Quantum Dots
摘要： A chiral phosphoric acid-catalyzed kinetic resolution and desymmetrization of para-quinols operating via oxa-Michael addition was developed and subsequently subjected to mechanistic study. Good to excellent s-factors/enantioselectivities were obtained over a broad range of substrates. Kinetic studies were performed, and DFT studies favor a hydrogen bonding activation mode. The mechanistic studies provide insights to previously reported chiral anion phase transfer reactions involving chiral phosphate catalysts in combination with boronic acids.
关键词： directed reactivity,oxa-Michael addition,kinetics,asymmetric catalysis,chiral phosphoric acid,reaction mechanisms
更新于2025-09-11 14:15:04