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Mesoporous TiO2-BiOBr Microspheres with Tailorable Adsorption Capacities for Photodegradation of Organic Water Pollutants: Probing Adsorption-Photocatalysis Synergy by Combining Experiments and Kinetic Modeling
摘要： Understanding adsorption-photocatalysis synergy helps advance solar-driven photodegradation of organic wastewater pollutants. To evaluate the synergy, mesoporous TiO2(amorphous)-BiOBr microspheres were facilely synthesized as model photocatalysts and characterized by XRD, SEM, TEM/HRTEM, XPS, nitrogen adsorption-desorption, UV-vis DRS, photoluminescence, and FTIR. The characterizations and photodegradation tests suggested that the composites had both adsorption sites and photocatalysis sites on BiOBr phase, while homogeneously distributed TiO2 in BiOBr microplates tailored the size of BiOBr crystallites. Accordingly, surface areas of the composites spanned from 22 to 155 m2/g and adsorption capacities for methyl orange (MO) ranged from 16 to 54 mg/g, controlled by the TiO2 content. In addition to experiments, kinetic modeling that combined adsorption with photocatalysis was developed and aided elucidating the synergy and quantitatively evaluating the composites with extracted rate constants from experimental data. The rate constant of the composite (Ti/Bi = 0.6) was calculated to be 3 times that of the pure BiOBr. Though adsorption promoted MO photodegradation, the capacity of the composite for MO adsorption and photodegradation decreased dramatically during the cycling tests. Nevertheless, this problem did not happen during photodegradation of rhodamine B and phenol on the composite and photodegradation of MO on pure BiOBr. This was explained by possible accumulation of degradation intermediates on the composite surface. This study provides a useful approach to investigate the adsorption-photocatalysis synergy from the perspectives of experiments and kinetic modeling and implies the necessity of scrutinizing the adverse effects of high levels of adsorption on recyclability of the photocatalysts.
关键词： Organic pollutants photodegradation,Kinetic modeling,TiO2-BiOBr microspheres,Tailorable adsorption capacities,Adsorption-photocatalysis synergy
更新于2025-11-14 17:03:37
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In situ laser reflectivity to monitor and control the nucleation and growth of atomically-thin 2D materials
摘要： The growth of atomically-thin two-dimensional (2D) layered and other quantum materials is typically performed without in situ monitoring or control. Here, a simple laser reflectivity approach is demonstrated to provide in situ control over sub-monolayer thickness and growth kinetics during pulsed laser deposition (PLD) of MoSe2 layers. First, the general technique is presented with emphasis on designing the maximum sensitivity of the optical contrast through consideration of Fresnel’s equations with proper choice of layer thickness, substrate, and laser monitoring wavelength, incidence angle, and laser polarization. Then the 633 nm optical reflectivity of MoSe2 layers on SiO2/Si substrates was predicted and compared with in situ monitoring of MoSe2 growth by PLD under actual growth conditions using a probe HeNe laser beam. The measurements showed high sensitivity and excellent agreement with MoSe2 surface coverages calculated from atomic resolution STEM analysis of 2D layers deposited in arrested growth experiments. Growth kinetics revealed by these measurements showed sigmoidal nucleation and growth stages in the formation of the 2D MoSe2 layers that are described by a simple model, indicating the promise of the laser reflectivity technique for in situ monitoring and control of 2D materials deposition.
关键词： pulsed laser deposition (PLD),MoSe2,kinetic modeling,in situ reflectivity,2D materials
更新于2025-09-16 10:30:52
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Prediction of Carbofuran Degradation Based on the Hydroxyl Radical’s Generation using the FeIII impregnated N doped-TiO2/H2O2/Visible LED Photo-Fenton-like Process
摘要： Hydroxyl radicals (?OH) are the dominant reactive species during most photocatalytic reactions. Therefore, ?OH generation as an index could be beneficial in comparing the obtained results in different experimental setup designs, thereby providing new insights for understanding the photocatalytic mechanism. Heterogeneous Photo-Fenton like processes are one of the most effective technologies for degradation of organic pollutants through ?OH production. Nevertheless, kinetic models that take into account the dependence of the contaminant degradation on ?OH generation under homogeneous oxidant supply, are still limited in such processes. In this paper, a photo-Fenton like reagent (FeIII impregnated N-doped TiO2 (FeNT)/H2O2) involving both heterogeneous and homogeneous phases was employed for carbofuran (CBF) degradation, frequently used pesticide in many developing countries from the carbamate group. In addition, a commercial visible LED lamp (Vis LED) with high power output was utilized as an innovative and efficient visible light source to simulate solar energy. Accordingly, a new kinetic model was proposed to predict CBF degradation in the FeNT/H2O2/Vis LED process under high Vis LED light intensities based on intrinsic reaction parameters, including the Vis LED light intensity, FeNT dosage, initial H2O2 concentration, and ?OH generation. The developed model was verified and validated successfully under various reaction conditions. However, a standard error ranging from 3 % to 15% was observed at extreme cases such as high [FeNT] and I or low [H2O2]0 when comparing model predictions and experimental results. This is due to the use of averaged conditions to forecast the rate constants.
关键词： Fe-N doped TiO2,Hydroxyl radicals,kinetic modeling,Carbofuran,Visible LED,impregnation
更新于2025-09-16 10:30:52
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An optimized and automated approach to quantifying channelrhodopsin photocurrent kinetics
摘要： Channelrhodopsins are light-activated ion channels that enable targetable activation or inhibition of excitable cells with light. Ion conductance can generally be described by a four step photocycle, which includes two open and two closed states. While a complete understanding of channelrhodopsin function cannot be understood in the absence of kinetic modeling, model fitting requires manual fitting, which is laborious and technically complicated for non-experts. To enhance analysis of photocurrent data, this manuscript describes a fitting program where electrophysiology data can be automatically and quantitatively analyzed. Significant improvement in this program when compare to our previous version includes 1) the ability to automatically find the experiment start time using the derivative of the current signal, 2) utilizing the Object Oriented Programing (OPP) paradigm which is significantly more reliable if the code is used by people with little to no programming experience and 3) the distribution of the code is simplified to sharing a single MATLAB file, including rigorous comments throughout. To demonstrate the utility of this program, we show automated fitting of photocurrents from two member proteins: channelrhodopsin-2 and a chimera between channelrhodopsin-1 and channelrhodopsin-2 (C1C2).
关键词： neuroscience,channelrhodopsin,optogenetics,kinetic modeling,electrophysiology
更新于2025-09-10 09:29:36
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Experimental and theoretical investigations of free radical photopolymerization: Inhibition and termination reactions
摘要： In this work, the inhibition and termination reactions occurring throughout a free radical photopolymerization initiated by a type-I photoinitiator are studied by kinetic modeling. The role of the macroradicals as the main oxygen trapping agents during the inhibition time is identified, and the absence of primary radical consumption by oxygen can be related to a high initiation efficiency at early times. The ratio of the termination reactions reveals that bimolecular termination remains the principal pathway for the cessation of macromolecule growth, even at high polymer conversion. Moreover, the evolution of the termination ratio during the polymerization can be correlated to both the diffusional control of the polymerization reactions as the polymer network grows and the photoinitiator consumption. Finally, the effect of the incident light intensity and the initial photoinitiator concentration on the termination reactions is assessed, and the validity of the steady-state assumption applied to the macroradical concentration discussed.
关键词： Oxygen inhibition,Kinetic modeling,Radical photopolymerization,Steady-state assumption,Type-I photoinitiator,Termination reactions
更新于2025-09-09 09:28:46