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Triplet-State Photochemistry of Dissolved Organic Matter: Triplet-State Energy Distribution and Surface Electric Charge Conditions
摘要： Excited triplet states of chromophoric dissolved organic matter (3CDOM*) are highly reactive species in sunlit surface waters and play a critical role in reactive oxygen species (ROS) formation and pollutant attenuation. In the present study, a series of chemical probes, including sorbic acid, sorbic alcohol, sorbic amine, trimethylphenol, and furfuryl alcohol, were employed to quantitatively determine 3CDOM* and 1O2 in various organic matters. Using a high concentration of sorbic alcohol as high-energy triplet states quencher, 3CDOM* can be first distinguished as high-energy triplet states (>250 kJ mol?1) and low-energy triplet states (<250 kJ mol?1). The terrestrial-origin natural organic matter (NOM) was found to mainly consist of low-energy triplet states, while high-energy triplet states were predominant in autochthonous-origin NOM and effluent/wastewater organic matter (EfOM/WWOM). The 1O2 quantum yields and electron transfer quantum yield coefficients (f TMP) generated from low-energy triplet states remained constant in all tested organic matters. External phenolic compound showed quenching effects on triplet-state formation and tended to have a higher quenching efficiency for aromatic ketone triplet states, which are the main high-energy triplet states. In comparison with terrestrial-origin NOM, autochthonous-origin NOM and EfOM/WWOM presented lower reaction rate constants for sorbic amines and higher reaction rate constants for sorbic acid, and these differences are likely due to dissimilar surface electric charge conditions. Understanding the triplet-state photochemistry of CDOM is essential for providing useful insights into their photochemical effects in aquatic systems.
关键词： surface charge,triplet-state photochemistry,energy distribution,dissolved organic matter,reactive oxygen species,chemical probes
更新于2025-11-19 16:56:35
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Controlling self-assembling and color-transition of polydiacetylene/zinc(II) ion/zinc oxide nanocomposites by varying pH: Effects of surface charge and head group dissociation
摘要： Polydiacetylene/zinc(II) ion/zinc oxide (PDA/Zn2+/ZnO) nanocomposite exhibits reversible thermochromism and dual colorimetric response to acid/base. This contribution presents our ongoing development of the PDA/Zn2+/ZnO nanocomposite for sensing applications by controlling ZnO surface charge and dissociation of PDA headgroup via pH adjustment. At pH >10, negative ZnO surface charge and PDA carboxylate headgroup significantly enhance molecular organization during the self-assembling process. An increase of the nanocomposite amount after photopolymerization is observed. Oppositely, pH <6 results in irreversible-thermochromic nanocomposites. Additionally, the nanocomposites prepared at different pH change color at different concentrations of chemical stimuli. Molecular packing, local interactions and PDA conformation are investigated.
关键词： self-assembling,color transition,sensor,polydiacetylene,dissociation,surface charge
更新于2025-09-23 15:23:52
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Polarization, inner and outer field and surface charge compensation of a molecular crystal
摘要： The polarization of molecules embedded in crystals is of fundamental importance for understand and modeling of dielectric properties of these materials. Typically, the simulations concern ideal crystals, meaning infinite objects lacking of any defect and of any truncation. But in real life, crystals of finite sizes, and containing defects, are used. In this work, we focus on the calculation of the polarization of crystals of 4-iodo-4’-nitrobiphenyl (belonging to the polar class mm2), by mimicking several finite sizes and analyzing the effects of surfaces. This simulation implies calculation of the inner electric field, starting from the dipole of each molecule or, for a better accuracy, of each atom in the crystal. Using the atomic/molecular polarizabilities, calculations are repeated iteratively until a self-consistency is achieved. These simulations enable calculation of the polarization of several kinds of crystal shapes, up to ca. 80 nm scale range. Needle-like crystals slightly enhance (10%) the average dipole moment in polar direction of the constituting molecules, compared to their values in vacuo, whereas plate-like crystals severely reduce it (ca. 50%). In real systems, the effects of screening charges on the crystal surfaces cannot be neglected. A simple model enables to calculate that the dipole of needle-like crystals, under the effect of compensating charges, can be reduced close to extinction. On the other hand, the situation of plate-like crystals does not differ significantly under the influence of screening charges.
关键词： polar crystals,compensation,outer electric field,polarization,surface charge density,inner electric field
更新于2025-09-23 15:21:21
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Aqueous Stable Ti3C2 MXene Membrane with Fast and Photo-Switchable Nanofluidic Transport
摘要： High, stable, and modulatable ionic conductivity is important for the wide nanofluidic applications of layered two-dimensional (2D) membranes. In this study, we demonstrate the orders of magnitude higher proton and ionic conductivity of Ti3C2Tx membrane than that of bulk solution at low concentrations. Importantly, the membrane is highly stable in aqueous solution without any modification, due to the strong interlayer van der Waals attractive interaction, and weak electrostatic repulsive interaction. Furthermore, by exploiting the intrinsic photothermal property of MXene, we demonstrate that the ionic conductivity can be reversely, rapidly, and completely switched on or off with laser light. This study should prove MXene membrane as an suitable platform to study and utilize nanofluidic ion transport. It should also inspire future studies to manipulate the mass transport through 2D membranes using their inherent physico-chemical properties.
关键词： photo-controlled,nanofluidic,surface charge,MXene,aqueous stability
更新于2025-09-23 15:21:21
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Designing Beveled Edge Termination in GaN Vertical p-i-n Diode-Bevel Angle, Doping, and Passivation
摘要： A series of electric field profile simulations in gallium nitride (GaN) p-i-n vertical diodes with negative bevel termination is carried out to optimize the bevel design. The bevel angles are varied from 90? to 0.1? with reasonably small increments to study the impact of the bevel angle on the electric field profile. The doping densities are also varied to study a more generalized trend; a new parameter defined as transition angle θt is proposed to characterize the effectivity of a beveled edge termination. Considering the potential dry etch damage on the bevel side-wall during device fabrication, the fixed surface charge from the dangling bonds and commonly used dielectric passivation are also added separately to investigate their influence. This article presents a comprehensive simulation study of GaN p-i-n diode with negative beveled edge termination, making it a useful guide for designing a simple and effective beveled edge termination, which eventually helps to enable the routine avalanche in GaN p-i-n diodes.
关键词： beveled edge termination,surface charge,simulation,gallium nitride (GaN),transition angle,silvaco,passivation,p-i-n diode,Avalanche,TCAD
更新于2025-09-23 15:21:01
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Carbon quantum dots modified anatase/rutile TiO2 photoanode with dramatically enhanced photoelectrochemical performance
摘要： Titanium dioxide (TiO2) is a promising photoanode material for photoelectrochemical (PEC) water splitting, but the severe bulk recombination of photongenerated carriers, the sluggish oxygen evolution reaction (OER) kinetics and the poor visible light response are the main bottleneck problems. Here, the carbon quantum dots (CQDs) modified anatase/rutile TiO2 photoanode (CQDs/A/R-TiO2) was designed by growth of anatase TiO2 nanothorns on the rutile TiO2 nanorods and further surface modification of CQDs. The results revealed that A/R-TiO2 heterojunction significantly suppressed the bulk recombination of photogenerated carriers. With further incorporation of CQDs into A/R-TiO2, dramatical improvement of OER kinetics and light harvesting were obtained. The bulk charge separation efficiency (ηbulk) and the surface charge injection efficiency (ηsurface) of CQDs/A/R-TiO2 are 1.69 and 5.74 times higher than that of the pristine TiO2 at 0.6 V vs. RHE, respectively. The photocurrent of CQDs/A/R-TiO2 is increased by 11.72 times and the onset potential of CQDs/A/R-TiO2 is negatively shifted by 240 mV.
关键词： Anatase/rutile TiO2 heterojunction,Carbon quantum dots,Bulk and surface charge transfer kinetics,PEC,Light harvesting
更新于2025-09-23 15:19:57
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Two Birds with One Stone: Manipulating Colloids Assembled into Amorphous and Ordered Photonic Crystals and Their Combinations for Coding-Decoding
摘要： Photonic crystals including amorphous and ordered photonic crystals (APCs and OPCs) show wide applications in color displays, sensors, and pigments. The fabrication of APCs and OPCs in one method is highly desired, however, it remains a big challenge due to the lack fine control the of the assemble behavior of the colloids. Herein, an efficient surface charge assisted colloidal assembly (SCACA) is developed to fabricate APCs with noniridescent structural colors and OPCs with iridescent colors by the co-assembly of aminated silica particles and nanosized carbon black (CB) in solution with different pH value. The surface charge of the particle is demonstrated to be the key to manipulate the assembly behavior of the particles, thus, the structure, defect, reflection intensity, and angle in/dependent structural color of the photonic crystals can be precisely controlled. Compared with previous strategies, SCACA is considerable simple and efficient in preparing APCs and OPCs which makes the fabrication more controllable, convenient and scalable. Moreover, through combing the noniridescent and iridescent structural colors of APCs and OPCs, a single color and multicolor based coding-decoding system are developed, in which the structural colors, numbers, positions, and angle in/dependency of codes can be hided and recognized by naked eyes at varied viewing angles. This work provides a new insight for precise manipulating the assembly of the colloids into APCs and OPCs, and extends their combined applications in anti-counterfeiting and information storage.
关键词： Surface charge assisted colloidal assembly,Photonic crystals,Coding-decoding system,Ordered photonic crystals,Amorphous photonic crystals
更新于2025-09-23 15:19:57
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An investigation on surface modified TiO2 incorporated with graphene oxide for dye-sensitized solar cell
摘要： In the present study, titanium dioxide (TiO2) nanoparticles were amine functionalized by using (3-aminopropyl) triethoxysilane (APTES) for the incorporation with graphene oxide (GO) to resolve the rapid agglomeration of nanoparticles. The zeta potentiometer revealed a significant increment of surface charge from 8.31 mV (un-treated) to 34.5 mV (treated) for the TiO2 nanoparticles which promotes strong electrostatic attraction with GO. Electrophoretic deposition technique was then employed for the fabrication of the photoanodes by generating an electric field for the transportation of the composite material. This work aimed to find the optimum loading content of GO-TiO2 for a higher photoconversion efficiency of the dye-sensitized solar cell (DSSC). Among the samples, the sample loaded with 0.5 g TiO2 showed the lowest emission peak intensity (Raman PL) which indicates efficient trapping of photogenerated electrons. By applying the Kubelka-Munk (K-M) expression, the absorbance spectra were converted into Tauc plots through which the aforementioned sample was found to exhibit a band gap energy of 2.91 eV (suitable for light absorption in the visible light region). The electron transfer efficiency for the sample loaded with 0.5 g TiO2 was relatively higher than the other samples in the DSSCs yielding a photoconversion efficiency of 6.86% because of the effective reduction in electron recombination.
关键词： Electrophoretic deposition,Photoconversion,Amine functionalized,DSSC,Surface charge
更新于2025-09-16 10:30:52
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Fast optical method for characterizing plasmonic nanoparticle adhesion on functionalized surfaces
摘要： In this paper, a rapid optical method for characterizing plasmonic (gold) nanoparticle (AuNP) adhesion is presented. Two different methods were used for AuNP preparation: the well-known Turkevich method resulted in particles with negative surface charge; for preparing AuNPs with positive surface charge, stainless steel was used as reducing agent. The solid surface for adhesion was provided by a column packed with pristine or surface-modified glass beads. The size of the nanoparticles was studied by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS); the surface charge of the components was determined by streaming potential measurements. The characterization of adhesion was performed in a flow system by UV-Vis spectroscopy. During the adhesion experiments, the role of the surface charge, the particle size, and the pH were studied, as well as the adhered amount of gold nanoparticles and the surface coverage values. The latter was estimated by theoretical calculations and defined by the quotient of the measured and the maximal adhered amount of nanoparticles, which could be determined by the cross-sectional area of the NPs and the specific surface area of the glass beads. The results are verified by the polarization reflectometric interference spectroscopy (PRIfS) method: silica nanoparticles with diameters of a few hundred (d~450) nanometers were immobilized on the surface of glass substrate by the Langmuir–Blodgett method, the surface was modified similar to the 3D (continuous flow packed column) system, and gold nanoparticles from different pH solutions were adhered during the measurements. These kinds of modified surfaces allow the investigation of biomolecule adsorption in the same reflectometric setup.
关键词： Adhesion,Reflectometric interference spectroscopy,Flow system,Optical method,Plasmonic nanoparticles,Surface charge
更新于2025-09-12 10:27:22
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European Microscopy Congress 2016: Proceedings || Quantitative measurement of doping and surface charge in a ZnO nanowire using in-situ biasing and off-axis electron holography
摘要： The measurement of doping and surface charge in a Zn2N3 nanowire using in-situ biasing and off-axis electron holography
关键词： surface charge,in-situ biasing,off-axis electron holography,Zn2N3 nanowire,doping
更新于2025-09-11 14:15:04