Surface Desorption Research Articles

The Influence of Solvent on Surface Adsorption and Desorption

The Influence of Solvent on Surface Adsorption and Desorption

Improved longevity of actomyosin in vitro motility assays for sustainable lab-on-a-chip applications

AbstractIn the in vitro motility assay (IVMA), actin filaments are observed while propelled by surface-adsorbed myosin motor fragments such as heavy meromyosin (HMM). In addition to fundamental studies, the IVMA is the basis for a range of lab-on-a-chip applications, e.g. transport of cargoes in nanofabricated channels in nanoseparation/biosensing or the solution of combinatorial mathematical problems in network-based biocomputation. In these applications, prolonged myosin function is critical as is the potential to repeatedly exchange experimental solutions without functional deterioration. We here elucidate key factors of importance in these regards. Our findings support a hypothesis that early deterioration in the IVMA is primarily due to oxygen entrance into in vitro motility assay flow cells. In the presence of a typically used oxygen scavenger mixture (glucose oxidase, glucose, and catalase), this leads to pH reduction by a glucose oxidase-catalyzed reaction between glucose and oxygen but also contributes to functional deterioration by other mechanisms. Our studies further demonstrate challenges associated with evaporation and loss of actin filaments with time. However, over 8 h at 21–26 °C, there is no significant surface desorption or denaturation of HMM if solutions are exchanged manually every 30 min. We arrive at an optimized protocol with repeated exchange of carefully degassed assay solution of 45 mM ionic strength, at 30 min intervals. This is sufficient to maintain the high-quality function in an IVMA over 8 h at 21–26 °C, provided that fresh actin filaments are re-supplied in connection with each assay solution exchange. Finally, we demonstrate adaptation to a microfluidic platform and identify challenges that remain to be solved for real lab-on-a-chip applications.

CO2 and NO2 formation on amorphous solid water

Context. The dynamics of molecule formation, relaxation, diffusion, and desorption on amorphous solid water (ASW) is studied in a quantitative fashion. Aims. The formation probability, stabilization, energy relaxation, and diffusion dynamics of CO2 and NO2 on cold ASW following atom+diatom recombination reactions are characterized quantitatively. Methods. Accurate machine-learned energy functions combined with fluctuating charge models were used to investigate the diffusion, interactions, and recombination dynamics of atomic oxygen with CO and NO on ASW. Energy relaxation to the ASW and into water internal degrees of freedom were determined from the analysis of the vibrational density of states. The surface diffusion and desorption energetics were investigated with extended and nonequilibrium MD simulations. Results. The reaction probability is determined quantitatively and it is demonstrated that surface diffusion of the reactants on the nanosecond time scale leads to recombination for initial separations of up to 20 Å. After recombination, both CO2 and NO2 stabilize by energy transfer to water internal and surface phonon modes on the picosecond timescale. The average diffusion barriers and desorption energies agree with those reported from experiments, which validates the energy functions. After recombination, the triatomic products diffuse easily, which contrasts with the equilibrium situation, in which both CO2 and NO2 are stationary on the multinanosecond timescale.

Introducing surface adsorption lithium storage mechanism to enhance safety of graphite

The thermal stability of lithiated graphite plays an important role in the thermal safety of lithium-ion batteries (LIBs). However, a safer graphite anode usually leads to a lower energy density. This article starts from multiple hazardous factors of lithiated graphite when thermal runaway occurs, considering the impact of defects on the electrochemical performance and thermal safety of graphite electrodes. In this study, turbostratic graphite was prepared as the anode for LIBs. The stacking of graphite was altered to form narrow pores and spherical aggregates, and introducing defects. By varying the ball-milling time, the structural changes of different ball-milled graphites were analyzed. The impact mechanism of defect structure on electrode electrochemical performance and safety performance was investigated. The results show that the spherical structure and large specific surface area are beneficial to increase the active sites and delay the self-heating of the battery. The formation of defects and pores increases the adsorption sites, which makes the surface adsorption of Li+ dominant and improves the ion diffusion. In addition, the dominance of surface adsorption and desorption effectively suppresses the problem of graphite flake peeling and intensified thermal runaway caused by graphite phase transition and lithium evolution heat release at high temperature. The thermal safety test was carried out by accelerated calorimeter (ARC), and its thermodynamics and reaction kinetics were quantitatively analyzed. It was proved that the introduction of surface adsorption lithium storage method successfully delayed the thermal runaway of the battery, realizing the balance between high electrochemical performance and high safety.

Optimizing Nitrate Reduction to Ammonia via Modulating Adsorption-Desorption Dynamics with High-Entropy CuNiCoZnMn Alloy Catalysts.

NO3RR synthesis of ammonia is a complex eight-electron reaction involving multiple steps and intermediates, in which NO3- adsorption and NH3 desorption are crucial. The Cu-based high entropy quinary alloy catalyst has good surface adsorption and desorption ability for the reduction of nitric acid to ammonia. Here, the catalytic sites were coordinated by constructing CuNiCoZnMn alloys to adjust the electronic structure of the catalytic sites to facilitate the reaction of the substrate and thus optimize the whole reaction path. Based on the ternary alloy CuNiCo, the introduction of the Zn element continues to reduce the desorption energy barrier, and the introduction of the Mn element continues to enhance the initial adsorption energy so that the target product can be quickly held and released to accelerate the production of ammonia. The NH3 yield and Faraday efficiency obtained for the quinary CuNiCoZnMn alloy catalyst reached 723.7 μmol h-1 cm-2 and 96.6%, respectively, at -0.35 V vs RHE potential. The density functional theory calculations showed that the quinary CuNiCoZnMn alloy (NO3- to *NO3-) initial adsorption-free energy change and (*NH3 to NH3) NH3 desorption-free energy change are -2.50, 0.072 eV, respectively, which are significantly better than those of the ternary CuNiC and quaternary CuNiCoZn of -2.02, 0.544 eV and -1.97, 0.217 eV.

Kinetic modelling of non-equilibrium plasma enhanced catalytic ammonia decomposition

It is important for the usage of ammonia as energy carrier to achieve ammonia decomposition at low temperature. In the present study, a reactor model of plasma catalytic ammonia decomposition over Fe catalyst at atmospheric pressure is developed in the aspect of plasma and chemical synergies kinetics. The plasma catalytic model accounted for multiple physical mechanisms in electronic and vibrational plasma kinetics and detailed ammonia decomposition mechanisms on the catalyst surface. In addition, a novel view that identify the surface chemisorption enhancement by plasma attributed to charge transfer via EMSI (electronic metal-support interaction) effect is highlighted. The result shows that the synergetic effect of plasma and thermal-catalyst is much greater than that of plasma or catalyst alone on ammonia decomposition, especially at low temperature. It is revealed that the surface desorption of nitrogen is still the rate-limiting step. Moreover, the numerical results also indicate that Langmuir-Hinshelwood reaction via 2 N(s)=>N2 is more likely to dominate the surface desorption of nitrogen in the presence of plasma rather than Eley-Rideal reaction via N + N(s)=>N2. At low electric field, there are infrequent free radicals (NH2, NH and N) and few vibrational ammonia (NH3(v)) generated by the plasma, thus considering that the adsorbed ammonia only undergoes a three-step dehydrogenation reaction. As a consequence, the rate of surface nitrogen desorption with plasma is greater than that with catalyst alone since plasma promotes the chemisorption process of ammonia. This work provides new fundamental insights into the synergistic effect of plasma and catalyst, as well as the direction for the ammonia decomposition catalyst design in plasma.

Probe into a novel surfactant-free microemulsion system of ethylene glycol monobutyl ether + water + diesel for crude oil removal and recovery from oily sludge

A novel surfactant-free microemulsion (SFME) system was proposed in this study, and applied in the crude oil removal and recovery from oily sludge (OS). Based on an investigation of the SFME phase behavior and solution properties, a complete ternary phase diagram was constructed. The SFME with three-liquid phase equilibrium (Winsor III type) was selected for the treatment of OS to achieve simultaneous efficient removal (up to 95.1 %) and recovery (up to 83.2 %) of crude oil. The SFME could be reused continuously for OS treatment without purification. The removal efficiency could still keep >75.9 % after 5 times of reuse, showing high reusability. The detached crude oil could be automatically recovered based on the phase equilibrium principle without additional separation. In the washing experiments, single-factor and multi-factor orthogonal tests were applied to investigate the effects of different experimental conditions on oil removal efficiency and determine the optimal experimental scheme. The treated OS was sufficiently decontaminated according to the morphology, composition, and properties analysis by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and contact angle. The composition of the recovered crude oil was identical to that of commercial crude oil according to gas chromatography–mass spectrometry analysis, showing a high recovery value. The kinetic analysis revealed that crude oil desorption experienced three main stages: membrane diffusion, intra-particle diffusion and surface desorption, and identified the chemisorption was the main interaction between the oil–soil. Finally, the mechanism of SFME action was assessed for dissolution and activation based on ultra-low IFT.

Two-hole “desorption” mechanism of interstitial-vacancy pair generation visualized by avalanche-like color-center yield in synthetic diamond under ultrashort-pulse laser exposure

A model sectorial synthetic Ib-diamond plate with a minor concentration of substitutional atomic nitrogen C-centers was exposed in its bulk by tightly focused 0.2-ps, 525-nm laser pulses, coming at 80-MHz repetition rate and nJ-level variable pulse energies. Structural conversion into NV- and other carbon vacancy/interstitial-related centers was observed by infrared, optical and 3D confocal photoluminescence (PL) microspectroscopy, exhibiting in the optical range the ultra-broad (UV-near-IR) and smooth (structureless) absorption/photoluminescence spectra. PL intensity measured at the selected 480 and 530-nm wavelengths demonstrates its third power of the corresponding pulse energy dependences (∝E3) and avalanche-like dynamics as a function of laser exposure. Our analysis of electron-hole plasma photoexcitation and related generation of non-thermalized Auger carriers as a function of laser pulse energy (∝E1/2 and ∝E3/2, respectively) indicates that the known two-hole Auger-induced surface desorption mechanism could be anticipated in bulk diamond for interstitial-vacancy Frenkel pair generation, which rate could be evaluated via structural conversion rate for C-centers. At higher pulse energies tremendous interstitial-vacancy Frenkel pair generation rates could result not only in structural conversion of impurity-based color centers, but also in ultrafast “non-thermal” structural disordering in diamond.

Investigating the influence of solvent type and pH on protein adsorption onto silica surface by evanescent-wave cavity ring-down spectroscopy.

Several studies have explored the adsorption of various proteins onto solid-liquid interfaces, revealing the crucial role of buffer solutions in biological processes. However, a comprehensive evaluation of the buffer's influence on protein absorption onto fused silica is still lacking. This study employs evanescent-wave cavity ring-down spectroscopy (EW-CRDS) to assess the influence of buffer solutions and pH on the adsorption kinetics of three globular proteins: hemoglobin (Hb), myoglobin (Mb), and cytochrome c (Cyt-C) onto fused silica. The EW-CRDS tool, with a ring-down time of and a minimum detectable absorbance of , enabled precise optical measurements at solid-liquid interfaces. The three heme proteins' adsorption behavior was investigated at pH 7 in three different solvents: deionized (DI) water, tris(hydroxymethyl)-aminomethane hydrochloride (Tris-HCl), and phosphate buffered saline (PBS). For each protein, the surface coverage, the adsorption and desorption constants, and the surface equilibrium constant were optically measured by our EW-CRDS tool. Depending on the nature of each solvent, the proteins showed a completely different adsorption trend on the silica surface. The adsorption of Mb on the silica surface was depressed in the presence of both Tris-HCl and PBS buffers compared with unbuffered (DI water) solutions. In contrast, Cyt-C adsorption appears to be relatively unaffected by the choice of buffer, as it involves strong electrostatic interactions with the surface. Notably, Hb exhibits an opposite trend, with enhanced protein adsorption in the presence of Tris-HCl and PBS buffer. The pH investigations demonstrated that the electrostatic interactions between the proteins and the surface had a major influence on protein adsorption on the silica surface, with adsorption being greatest when the pH values were around the protein's isoelectric point. This study demonstrated the ability of the highly sensitive EW-CRDS tool to study the adsorption events of the evanescent-field-confined protein species in real-time at low surface coverages with fast resolution, making it a valuable tool for studying biomolecule kinetics at solid-liquid interfaces.

Deuterium uptake, desorption and sputtering from W(110) surface covered with oxygen

Rate equation modelling is performed to simulate D2 and D2+D2+ exposure of the W(110) surface with varying coverage of oxygen atoms (O) from the clean surface up to 0.75 monolayer of O. Density Functional Theory (DFT) calculated energetics are used as inputs for the surface processes and desorption energies are optimized to best reproduce the Thermal Desorption Spectrometry (TDS) experiments obtained for D2 exposure. For the clean surface, the optimized desorption energies (1.10 eV–1.40 eV) are below the DFT ones (1.30 eV–1.50 eV). For the O covered surface, the main desorption peak is reproduced with desorption energies of 1.10 eV and 1.00 eV for 0.50 and 0.75 monolayer of O respectively. This is slightly higher than the DFT predicted desorption energies. In order to simulate satisfactorily the total retention obtained experimentally for D2+D2+ exposure, a sputtering process needs to be added to the model, describing the sputtering of adsorbed species (D atoms) by the incident D ions. The impact of the sputtering process on the shape of the TDS spectra, on the total retention and on the recycling of D from the wall is discussed. In order to better characterize the sputtering process, especially its products and yields, atomistic calculations such as molecular dynamics are suggested as a next step for this study.

Spatially- and time-resolved measurements of HO2 radicals in a ns pulse atmospheric pressure plasma jet

The absolute, spatially-resolved, and time-resolved number density of the hydroperoxyl radical is measured in a quasi-two-dimensional, atmospheric pressure ‘curtain’ plasma jet powered by a train of ns discharge pulses. The spatial distribution of HO2 is measured across the shorter dimension of the jet. The measurements are made in two different configurations, (a) H2O–O2–He jet impinging on a copper foil target, and (b) O2–He jet incident on the liquid water surface. In the first configuration, the water vapor is added to the O2–He flow in a bubbler filled with distilled, deionized water. The measurements are made using the previously developed pulsed cavity ring down spectroscopy diagnostic near 1.5 μm. The ring-down cavity is formed between two high-reflectivity mirrors placed at the ends of the stainless steel ‘arms’ purged with dry air, with the plasma jet placed in the gap between the arms. The objectives of this work are to use the HO2 number density to assess the accuracy of the modeling predictions using a previously developed ‘global’ reaction mechanism, and to estimate the efficiency of hydrogen peroxide generation in the ns pulse discharge plasma. HO2 was detected only in the first configuration, most likely due to the rapid decay of the metastable He atoms and O atoms generated in the plasma, which prevents the generation of H atoms (dominant HO2 precursors) in the evaporation/mixing layer. Both the water vapor in the jet and HO2 generated in the plasma have been measured. The results exhibit a rapid accumulation of HO2 during the ns pulse discharge burst, followed by the decay in the afterglow on a ms time scale. The kinetic model overpredicts the quasi-steady-state HO2 number density, as well as the HO2 decay rate after the discharge is turned off. The relatively slow HO2 decay in the afterglow suggests that it may be affected by diffusion, along with the surface adsorption and desorption of radicals. The present approach demonstrates the utility of a 2D curtain plasma jet for the line-of-sight absorption spectroscopy measurements of radicals and excited species present in small concentrations in ambient plasma environments.

Mechanism of Phosphate Desorption from Activated Red Mud Particle Adsorbents.

Herein, activated red mud particles are used as adsorbents for phosphorus adsorption. HCl solutions with different concentrations and deionized water are employed for desorption tests, and the desorption mechanism under the following optimal conditions is investigated: HCl concentration = 0.2 mol/L, desorbent dosage = 0.15 L/g, desorption temperature = 35 °C, and desorption time = 12 h. Under these conditions, the phosphate desorption rate and amount reach 99.11% and 11.29 mg/g, respectively. Notably, the Langmuir isothermal and pseudo-second-order kinetic linear models exhibit consistent results: monomolecular-layer surface desorption is dominant, and chemical desorption limits the rate of surface desorption. Thermodynamic analysis indicates that phosphorus desorption by the desorbents is spontaneous and that high temperatures promote such desorption. Moreover, an intraparticle diffusion model demonstrates that the removal of phosphorus in the form of precipitation from the surface of an activated hematite particle adsorbent primarily occurs via a chemical reaction, and surface micromorphological analysis indicates that desorption is primarily accompanied by Ca dissolution, followed by Al and Fe dissolutions. The desorbents react with the active elements in red mud, and the vibrations of the [SiO4]4- functional groups of calcium-iron garnet and calcite or aragonite disappear. Further, in Fourier-transform infrared spectra, the intensities of the peaks corresponding to the PO43- group considerably decrease. Thus, desorption primarily involves monomolecular-layer chemical desorption.

Development and testing of silica gel with graphite powder composite adsorbent for cooling applications

This research work discusses the development and testing of innovative composite adsorbents made of silica gel (SG), polyvinyl alcohol (PVA) binder and graphite powder (GP). The investigation examines the specific surface area, thermal conductivity, pore volume, adsorption, and desorption rate of the synthesized composite adsorbent. Out of the various formulations, Composite A (composed of 93 % SG, 5 % GP, and 2 % PVA) demonstrates the specific surface area of 530.37 m2/g and pore volume of 0.497 cm3/g. It is noteworthy that Composite A exhibits a 14 % improvement in thermal conductivity and a 3 % increase in desorption rate when compared to its original material, while consistently maintaining the requisite mass transfer characteristics. There is significant improvement in the thermal conductivity of the composite adsorbents with the addition of more than 5 % GP. However, in addition to this enhancement, there is a reduction in adsorption capacity. X-ray diffraction investigation indicates that the composite adsorbents are thermally stable.FESEM investigation reveals that the composite A exhibit no signs of agglomeration. The suggested composite adsorbent show superior thermophysical attributes compared to both pure and silica gel-based composites, making them promising for achieving optimal performance in adsorption cooling systems (ACS), particularly with respect to the specific cooling power (SCP) and coefficient of performance (COP).

Surface Adsorption and Air Damping Behavior of β‐Ga2O3 Nanomechanical Resonators

AbstractBeta gallium oxide (β‐Ga2O3) has emerged as a highly promising semiconductor material with an ultrawide bandgap ranging from 4.5 to 4.9 eV for future applications in power electronics, optoelectronics, as well as gas and ultraviolet (UV) radiation sensors. Here, surface adsorption and air damping behavior of doubly clamped β‐Ga2O3 nanomechanical resonators are probed and systemically studied by measuring the resonance characteristics under different gas and pressure conditions. High responsivities of resonance to pressure are obtained by heating the devices up to 300 °C to induce an accelerated adsorption–desorption process. The initial surface conditions of the β‐Ga2O3 thin film play important roles in affecting the resonant behavior. UV ozone treatment proves effective in altering the initial surface conditions of β‐Ga2O3 nanosheets by eliminating physisorbed contaminants and filling oxygen vacancy defects residing on the surface, resulting in a consequential and discernible modification of the resonance behavior of β‐Ga2O3 nanomechanical resonators. The surface adsorption and desorption processes in β‐Ga2O3 demonstrate clear reversibility by exposing the UV treated β‐Ga2O3 to air. This study attains first‐hand information on how the surface conditions of β‐Ga2O3 affect its mechanical properties, and helps guide future development of transducers via β‐Ga2O3 nanoelectromechanical systems (NEMS) for pressure sensing applications, especially in harsh environments.

Investigation of Surface Affinity and Desorption Kinetics of Mixture of Volatile Organic Compounds on CuO-Based Resistive Gas Sensors

Investigation of Surface Affinity and Desorption Kinetics of Mixture of Volatile Organic Compounds on CuO-Based Resistive Gas Sensors

Effect of water vapor desorption on the performance of gallium nitride field emitter array

We are exploring the potential of gallium nitride (GaN) field emitter arrays in vacuum channel transistors. This study investigated the impact of ultraviolet (UV) light on the emission properties of large arrays of GaN field emitters. Arrays of 150 × 150 emitters were analyzed before and after UV exposure. With a constant collector voltage of 200 V DC, gate voltage sweeps from 0 to 60 V were applied. The initial I–V measurements showed a rapid increase in emission current, indicating a conditioning effect, settling at a stable value of 1.25 μA after three to five sweeps. Remarkably, exposure to UV light resulted in a fivefold increase in the maximum field emission current, reaching an impressive 6 μA. This significant enhancement highlights the potential of UV treatment for improving the performance of GaN-based field emitters. This surge in current can be attributed to the desorption of water vapor caused by the UV light. To compare with the heating-based water desorption technique, another array of 150 × 150 emitters was characterized before and after heating at 400 °C. While the collector voltage remained constant at 200 V DC, the gate voltage was systematically increased from 0 to 75 V in this experiment. This controlled sweeping of the gate voltage provided a precise method for characterizing the field emission properties of the GaN emitters. The I–V measurements revealed that, similar to the UV exposure case, collector current increased by approximately four times after heat treatment at 400 °C for 10 min. This resulted in a maximum field emission current of around 10 μA at 75 V. As with the UV case, this increase can also be attributed to surface desorption, primarily of water.

Improved external quantum efficiency of deep UV LEDs with an ultra-thin AlGaN last quantum barrier by controlling the desorption-kinetics process

An ultra-thin AlGaN last quantum barrier (LQB) with a high Al content is effective in enhancing the hole injection in AlGaN-based deep UV LEDs (DUV-LEDs). However, it is very challenging to realize the ultra-thin LQB by the metalorganic chemical vapor deposition technique. In this work, a well-defined 1.0 nm thick AlGaN LQB with unintentionally high Al content was achieved by controlling the surface desorption kinetics for the growth of multiple quantum wells. The light output power of the DUV-LEDs with 1 nm thick LQB was increased by 44% to 7.16 mW at 40 mA, and the peak external quantum efficiency reached 4.04%.

Particle growth across the scales: A combination of ab initio, molecular dynamics, and kinetic Monte Carlo simulations for Fe2Al5 in liquid Zn

We study the growth of Fe2Al5 particles in liquid Zn with a multi-scale approach from ab initio molecular statics and dynamics to kinetic Monte Carlo (kMC) simulations. This includes computation of the transition rates, i.e. adsorption rates from diffusion of elements in liquid Zn and desorption rates from surface desorption energies and interaction energies of atoms at the surface. Adsorption and desorption rates together with the correct crystal structure are the main input for the kMC simulations. With systematic kMC simulations, we then map out the growth rates of Fe2Al5 at different temperatures and varying chemical compositions. Altogether, this constitutes an approach that is also applicable to other studies focusing e.g. on deposition processes or dissolution of particles.

Quantitative characterization of the interfacial transition zone around lightweight and normal aggregates in cement mortars at different water-to-binder ratios

The interfacial transition zone (ITZ) between aggregates and cement binders has long been known as the most vulnerable to crack resistance among the three phases in heterogeneous concretes [i.e., aggregate, ITZ, cement binders] owing to its porous microstructure. The characteristics of the ITZ are determined by the aggregate types, water-to-binder (W/B) ratios, and supplementary cementitious materials. Furthermore, the correlations between the physicochemical properties of the interface in the vicinity of saturated lightweight aggregates (LWAs) and the mechanical properties of cement concretes are still controversial because of the rough surface and ambiguous water desorption behavior of LWAs. To clarify such correlations, in this study we systemically investigated the effect of different water desorption behaviors of LWAs in cement mortars for various W/B ratios ranging from 0.2 to 0.5 on the mechanical properties of cement mortars via isothermal calorimetry tests, scanning electron microscopy, and nanoindentation grid tests. In addition, the experimental results were compared to those of mortars containing fine normal-weight aggregates (NWAs). These investigations clarified the effect of mechanical properties and porosity of the ITZ on the inherent strength of cement mortars with different aggregate types and W/B ratios. An improvement in the ITZ morphology around the LWAs was observed in relation to that around the NWAs for W/B > 0.3. Conversely, the porosity increased significantly on the LWA surface with respect to that on the NWA surface for W/B = 0.2. Nanoindentation tests revealed the deterioration of the elastic moduli and hardness of mortars containing LWAs at all investigated W/B ratios.

Pore Size Dependence of Mass Transfer of Zinc Myoglobin in a Single Mesoporous Silica Particle.

This study investigated the pore size dependence of the mass transfer of zinc myoglobin (ZnMb) in a single mesoporous silica particle through confocal fluorescence microspectroscopy. The ZnMb's fluorescence depth profile in the particle was analyzed by a spherical diffusion model, and the intraparticle diffusion coefficient was obtained. The intraparticle diffusion coefficient in the silica particle with various pore sizes (10, 15, 30, and 50 nm) was furthermore analyzed based on a pore and surface diffusion model. Although the mass transfer mechanism in all silica particles followed the pore and surface diffusion model, the adsorption and desorption of ZnMb affected the mass transfer depending on the pore size. The influence of the slow desorption of ZnMb became pronounced for large pore sizes (30 and 50 nm), which was revealed by simulation using a diffusion equation combined with the adsorption-desorption kinetics. The distribution of ZnMb was suppressed in small pore sizes (10 and 15 nm) owing to the adsorption of ZnMb onto the entrance of the pore. Thus, we revealed the mass transfer mechanism of ZnMb in the silica particle with different pore sizes.