Deposition Phenomena Research Articles

Establishment of the New Zealand white rabbit animal model of fatty keratopathy associated with corneal neovascularization.

The term fatty keratopathy is used to describe the phenomenon of fat deposition caused by corneal neovascularization, which will severely affect the eye’s beauty and vision. The purpose of this study was to establish a New Zealand white rabbit animal model of fatty keratopathy, that is, the establishment of an animal model of fatty keratopathy. The goal was achieved by the combination of a corneal neovascularization animal model and a hyperlipidemia animal model. Two groups were created according to the experimental sequence. The first group initially induced a corneal neovascularization pattern and later induced a hyperlipidemia pattern, and the second group followed the opposite sequence. The results of the two groups showed that all the significant crystalline deposits of the cornea were visible. So the animal models of fatty keratopathy were successfully established in both groups.

An experimental investigation in the formation damage mechanism of deposited coke in in-situ combustion process using nuclear magnetic resonance

The success of an in situ combustion process is dependent on the stability and movement of the combustion front. During an in situ combustion process, coke is an important product for maintaining the stability of the combustion front. However, before being consumed by the combustion reaction, coke is deposited in the porous media; thus, it may cause the blockage of the pore throat and affect the subsequent air injection. In this study, the low-field nuclear magnetic resonance technique was applied to examine the influence of oxidized coke and pyrolyzed coke on the porous media. The results revealed that the coke deposition phenomenon was considerable in porous media and affected porosity. The formation damage was considerably severe in oxidized coke because of the drastic low-temperature oxidation. In case of the pyrolyzed core, the influence of coke on porosity is limited because of the low amount of coke generation. The average reduction in porosity was 21.90%, while that of the pyrolyzed coke is only 9.09%. Montmorillonite had the greatest catalytic effect on coke deposition for both oxidation and pyrolysis processes. Illite, kaolinite, and chlorite have an impact on coke deposition; however, because the change in porosity is attribute to a combination of multiple factors, the result is a lack of regularity. Heat causes the pore to reform and the fracture to form. The change in porous media can reduce the impact of coke deposition phenomenon on total porosity. Because of the high-temperature environment, this influence is more pronounced in the pyrolyzed core.

(Keynote) Fundamental Origin of the Electroless Pb Monolayer Deposition and Its Implications for Electroless Atomic Layer Deposition

In this talk, we point out a novel opportunity for catalyst monolayer and core-shell structures synthesis via surface limited redox replacement (SLRR) reaction. It is enabled by discovery of an electroless Pb monolayer deposition phenomenon whose fundamentals and practical aspects are presented. The particular benefit of this synthesis approach is for metal substrates which are not part of a broadly conductive supports such as metal nanoparticles imbedded in various oxides or zeolites. Examples of the catalyst monolayer deposition via SLRR of electrolesslly deposited Pb monolayer are presented under the auspices of a two-step electroless atomic layer deposition process (e-less ALD). Each cycle of the e-less ALD produces a precise submonolayer amount of catalyst deposit demonstrating its potential for a broad range of applications including synthesis of the oxide-supported catalyst core-shell structures or surface selective metallization in microelectronics. Figure 1

A study on droplets dispersion and deposition characteristics under supersonic spray flow for nanomaterial coating applications

Supersonic spray coating of nanomaterials, owing to high impact velocity of particles, offers significant potential to improve the physical and mechanical properties of target surfaces. Rather than handling individual light nano-scale particles directly with a number of limitations, aqueous nanomaterial colloids and suspensions can be supersonically deposited onto surfaces by converting these complex liquid mixtures into the form of atomized micro-scale droplets. Dispersion and deposition characteristics of these droplets play a vital role in the quality and efficacy of the resultant nanomaterial coating. In the present study, comprising numerical modeling and experimental validation, we investigate details of the dispersion and deposition characteristics of droplets under supersonic flow conditions. In the numerical study, a two-way coupled discrete phase modeling is used to track the discrete phase (i.e., droplets) and to investigate the interaction of droplets with the continuous gas phase (i.e., high-velocity driving gas) in regard to their properties and conditions. The results through computational fluid dynamics (CFD) show that driving gas properties (i.e., temperature, pressure, gas type) and droplet size play a prominent role in droplets dispersion and deposition phenomena. In particular, smaller droplets (≤2 μm) are observed to be more susceptible to turbulent dispersion and evaporation. In the experimental study, an atomization-based supersonic spray system is developed for model validation and a case example of nano-coating applications. The CFD modeling results are validated by particle image velocimetry (PIV) measurements. A case study of titanium dioxide (TiO2) nanomaterial coating on a polymer substrate (ITO/PET film) is performed to demonstrate the suitability of the present spray deposition system, which also addresses the current challenges of TiO2 coating onto ITO/PET surface.

Syngas production by chemical looping co-gasification of rice husk and coal using an iron-based oxygen carrier

The chemical looping co-gasification (CLCG) of rice husk and coal using iron ore as an oxygen carrier was carried out in a fixed bed reactor. The effects of different parameters including oxygen/carbon ratio, reaction temperature, steam flow rate, and rice husk blending ratio on the gasification performance were studied. Based on the carbon conversion efficiency, gasification efficiency, and gas yield, the optimal conditions of the CLCG of rice husk and coal were determined. Moreover, the synergistic effect in carbon conversion and syngas production between those two fuels was also analyzed. The results showed that the carbon conversion efficiency, gasification efficiency, and gas yield reached 88.16%, 49.23%, 1.14 Nm3/kg, respectively at the oxygen/carbon ratio of 0.2, the reactor temperature of 900 °C, the steam flow rate of 0.125 g/min, and the rice husk blending ratio of 50%. At this condition, there were significant synergistic effects between rice husk and coal during the CLCG process, and the synergistic rate for carbon conversion efficiency and gasification efficiency reached 21.54% and 3.62%, respectively. The SEM-EDX analysis showed that adding coal to rice husk could alleviate the ash deposition phenomenon on the surfaces of iron ore during the CLCG process.

Oblique angle deposition of boron carbide films by magnetron sputtering

Many applications of boron carbide (B4C) films entail deposition on non-planar substrates, necessitating a better understanding of oblique angle deposition phenomena. Here, we systematically study the effect of substrate tilt on properties of B4C films with thicknesses up to 10 μm deposited by direct current magnetron sputtering. Results show that all films are amorphous and columnar with an average column width of ∼100 nm, independent of substrate tilt. Column tilt angles are limited to ∼20° even for substrate tilt of 80°. Film density, residual stress, and the refractive index weakly (within ≲20%) depend on substrate tilt. Oxygen impurities bond preferentially with carbon atoms in inter-columnar regions. Substrate tilt has a major effect on mechanical properties that decrease by ∼50%, suggesting weak interconnection between nano-columns. Implications of these observations for the deposition onto non-planar substrates are discussed.

Numerical simulation of the solidification phenomena of single molten droplets impinging on non-isothermal flat plate using explicit moving particle simulation method

In jet engines and gas turbines, the deposition phenomenon is attributed to the adhesion of molten droplets on walls. In this study, numerical simulations of the deposition phenomena on a substrate were performed using the explicit moving particle simulation (E-MPS) method. We adopted a non-isothermal condition for the substrate using a coupling method including wall particles and a regular grid to estimate the heat conduction to and within the substrate for enhanced numerical accuracy. This coupling method was validated by comparing the theoretical values of the one-dimensional unsteady heat conduction. Simulations were performed to study the solidification phenomena of a single molten stannum (Sn) droplet impinging and solidifying on a vertical substrate. The droplet behavior from impingement to solidification shows reasonable agreement with experimental results in terms of spread factor, taking into account the heat exchange between the droplet and substrate, including the substrate temperature change. Although temperature change in the substrate is limited to areas near the impinging droplet, temperature distributions on the interface differ between the early and later stages. The high-temperature region appears near the impinging center except near the stagnation point for the former stage, while it is near the center for the latter stage. The finger and bump shapes around the impinging droplet are explained via Rayleigh–Taylor and Plateau–Rayleigh instabilities, respectively, using the actual expanding acceleration of the liquid film.

An Eulerian Single-Phase Transport Model for Solid Fission Products in the Molten Salt Fast Reactor: Development of an Analytical Solution for Verification Purposes

Nuclear reactor modeling has been shifting, over the last decades, towards full-core multiphysics analysis due to the ever-increasing safety requirements and complexity of the designs of innovative systems. This is particularly true for liquid-fuel reactor concepts such as the Molten Salt Fast Reactor (MSFR), given their strong intrinsic coupling between thermal-hydraulics, neutronics and fuel chemistry. In the MSFR, fission products (FPs) are originated within the liquid fuel and are carried by the fuel flow all over the reactor core and through pumping and heat exchange systems. Some of FP species, in the form of solid precipitates, can represent a major design and safety challenge, e.g., due to deposition on solid boundaries, and their distribution in the core is relevant to the design and safety analysis of the reactor. In this regard it is essential, both for the design and the safety assessment of the reactor, the capability to model the transport of solid FPs and their deposition to the boundary (e.g., wall or heat exchanger structures). To this aim, in this study, models of transport of solid FPs in the MSFR are developed and verified. An Eulerian single-phase transport model is developed and integrated in a consolidated multiphysics model of the MSFR based on the open-source CFD library OpenFOAM. In particular, general mixed-type deposition boundary conditions are considered, to possibly describe different kinds of particle-wall interaction mechanisms. For verification purposes, analytical solutions for simple case studies are derived ad hoc based on the extension of the classic Graetz problem to linear decay, distributed source terms and mixed-type boundary conditions. The results show excellent agreement between the two models, and highlight the effects of decay and deposition phenomena of various intensity. The resulting approach constitutes a computationally efficient tool to extend the capabilities of CFD-based multiphysics MSFR calculations towards the simulation of solid fission products transport.

Long-term thermal oxidative deposition of RP-3 jet fuels: Mechanism and modeling

The long-term thermal oxidative deposition of jet fuel is of great significance for the design and applications of the fuel-cooled thermal management of advanced aircrafts. In this paper, the long-term (100 h) thermal oxidative deposition of RP-3 jet fuel was carried out in the electric heating tube to understand the complex time-dependent deposition phenomena and behaviors. It was found that there are three typical deposition rates stages in 100 h time-on-stream (TOS) experiment, i.e., the initial stage, the growth stage, and the decline stage. In the initial stage (0–2 h), the average deposition rate continuously decreases by almost 5 times from 8.70 mg/h at 0 h to 1.73 mg/h at 2 h ascribed to the gradual coverage of metal surface by the deposition, and then grows by 4.37 times from 1.73 mg/h at 2 h up to 7.56 mg/h at 70 h attributed to the increased wall surface area from 0.01074 m2 to 0.02483 m2 by the solid deposit in growth stage. However, in the decline stage the average deposition rate slightly decreases to 7.08 mg/h at 100 h as a result of the reduction of local residence time as well as the possible aging of deposition layer. A simplified kinetic model of long-term thermal oxidative deposition process was proposed to describe the complex deposition rate variation and validated that the error between the prediction of total deposition amount and the experimental data is less than 10%.

Deposition Pattern Analysis on a Fouled Multistage Test Compressor

Abstract Compressor fouling is one of the main causes of gas turbine performance degradation. Microsized particles adhere to the blade surfaces increasing the surface roughness and modifying the airfoil shape. In this work, the contamination of the Allison 250 C18 multistage compressor engine with four sorts of micrometric dust has been provided. The tests were performed changing the relative humidity (RH) at the compressor inlet and the unit rotational speed. After each test, a photographic inspection of the internal fouled parts has been realized and the digital pictures have been analyzed employing an image processing package. The deposit's build-up of stator vanes and rotor blades has been postprocessed and the most affected regions of each compressor stage have been highlighted. Besides, a numerical simulation of the machine has been performed. The numerical flow field has been used to highlight the blade regions, which show the most favorable conditions for particle deposition. A theoretical model has been applied to the flow field to simulate the particle deposition. The combination of the deposition model with the results of the numerical simulations gives the chance to better understand the experimentally founded deposition patterns. Those results have been finally compared to the pictures of the patterns. The possibility to detect and measure the deposition patterns on a rotating test rig and the comparison with models and experiments gave the possibility to assess in detail the particle deposition phenomenon on a multistage axial compressor flow path.

Analysis of microparticle deposition in the human lung by taguchi method and response surface methodology

The deposition phenomenon of microparticle and SAR-CoV-2 laced bioaerosol in human airways is studied by Taguchi methods and response surface methodology (RSM). The data used herein is obtained from simulations of airflow dynamics and deposition fractions of drug particle aerosols in the downstream airways of asthma patients using computational fluid dynamics (CFD) and discrete particle motion (DPM). Three main parameters, including airflow rate, drug dose, and particle size, affecting aerosol deposition in the lungs of asthma patients are examined. The highest deposition fraction (DF) is obtained at the flow rate of 45 L min−1, the drug dose of 200 μg·puff−1, and the particle diameter of 5 μm. The optimized combination of levels for the three parameters for maximum drug deposition is performed via the Taguchi method. The importance of the influencing factors rank as particle size > drug dose > flow rate. RSM reveals that the combination of 30 L min−1, 5 μm, 200 μg·puff− has the highest deposition fraction. In part, this research also studied the deposition of bioaerosols contaminated with the SAR-CoV-2 virus, and their lowest DF is 1.15%. The low DF of bioaerosols reduces the probability of the SAR-CoV-2 virus transmission.

Pore-Scale Simulations of Particles Migration and Deposition in Porous Media Using LBM-DEM Coupling Method

This paper studies the migration and deposition of suspended particles in porous media. This problem results from the fact that during the operation of a groundwater source heat pump, the recharging process will contribute to the impairment of soil permeability. A coupling lattice Boltzmann method, discrete element method and immersed moving boundary method were used to investigate the migration of particles in porous media. The DKT (Drifting, Kissing, Tumbling) phenomena were employed to validate our program. The coupled effects of concentration, flow rate and pH on the clogging mechanism of the porous media were analyzed. Results show that, due to the repulsive barrier between the particles and porous media, there is a critical velocity. At a low flow rate, the deposition ratio increases with the increase in velocity. Beyond the critical velocity, the deposition ratio decreases when the velocity increases due to higher shear force. Permeability impairment increases with the increase in concentration, especially in the low flow rate condition. Changes in pH mainly affect the repulsive barrier. For a low flow rate, the decrease in repulsive barrier greatly promotes the deposition of particles. Under the condition of favorable deposition, the increase in flow rate reduces the deposition phenomenon. Under the condition of unfavorable deposition, the lower flow rate condition has a lower deposition ratio. The process of particle deposition and the dynamic motion after deposition were observed such as particles gliding over the surface. Accumulated particles in the downstream form bridges and hinder fluid flow. At a high flow rate, strong shear force is more capable of destroying bridges and recovering permeability. Adsorbed particles glide on the surface of the grain and deposit in the downstream. This paper aims to help understanding of the micro-events of particle deposition and the clogging process.

Simulation and verification of thermal conductivity of CuCr30 contact material based on morphological changes of Cr particles

In order to improve the thermal deposition of CuCr contact material for vacuum interrupter, CuCr30 contact material was treated with large deformation treatment to change the morphology and distribution of Cr particles, and the effect of the morphology change of Cr particle on the thermal conductivity of CuCr30 contact material was studied. At the same time, the finite element simulation of the thermal transfer behavior of the extruded and cast CuCr30 contact materials was carried out by using ANSYS software. The studies show that the large deformation treatment (deformation ratio 16:1) changes the morphology and distribution of Cr particles in CuCr30 contact material, making it change from dendritic to longitudinally arranged quasi-fibrous. Influenced by the morphology and distribution of Cr particles, the thermal conductivity of CuCr30 contact material is anisotropic, and the effective thermal conductivity varies significantly with the direction. Indeed along the deformation direction, the thermal conductivity of the extruded state is obviously higher than that of the cast state, increasing by 5.8 %. However, perpendicular to the extrusion direction, the thermal conductivity has little changes, and obvious deposition phenomenon appears in the process of thermal conduction. The finite element simulation results of the effective thermal conductivity of CuCr30 material by ANSYS are in good agreement with the measured results, and the error range is 0.7 %∼1%.

Numerical modeling of bed deposition in rapid flow-like landslides: a case study of the Gaolou landslide in Shaanxi Province, China

Some flow-like landslides tend to lose materials while moving on a relatively dry sliding surface. This phenomenon is called bed deposition. In contrast to the bed entrainment phenomenon, bed deposition is relatively poorly understood. Therefore, an improved depth-averaged model is proposed to quantify this phenomenon. The deposition depth is calculated according to the momentum conservation of the deposited mass, and the rheological property of the sliding mass on the bottom is modified considering an abrupt increase in the depth of the sliding surface after deposition. Utilizing the proposed model, the Gaolou landslide, a typical flowlike landside occurring on October 6th, 2006 with an obvious bed deposition phenomenon in Shaanxi Province of China, is simulated to investigate the influence of bed deposition on its propagation process. The results indicate that the proposed model can effectively depict the bed deposition phenomenon in the Gaolou landslide. Bed deposition dissipates part of the kinetic energy of this landslide; thus, the simulated debris inundation area would likely be overestimated when this effect is neglected. On the other hand, the thin liquefied layer formed by the bed deposition process reduces the friction energy dissipation, contributing to the high mobility of this landslide.

Seasonal variation of atmospheric bulk deposition along an urbanization gradient in Nuevo Leon, Mexico

Bulk deposition was studied along an urbanization gradient in the state of Nuevo Leon, Mexico. During a yearlong period seven sites within the Metropolitan Area of Monterrey (MAM) and two rural sites (Allende and Linares) were monitored, with the purpose of characterizing deposition and identifying possible patterns between sites. A total of 32 rainfall events were collected. An average pH of 7.15 ± 0.02 was found, which indicates the presence of neutralizing substances in rainwater, as well as an average Electrical Conductivity of 153.96 ± 6.83 μS/cm. The annual accumulated deposition follows the descending order Ca> K> Mg> Zn> Fe> Mn> Cu> Cd> Ni and does not show significant differences between urban and rural areas, with the exception of Ca (p = 0.017). The Principal Component Analysis shows that metals (Cu, Zn, Ni, Mn, and Cd) represent an important pathway in the deposition phenomena and this behavior is maintained through the urbanization gradient, which denotes that the rural areas could be connected to the air basin of the MAM. Seasonal deposition showed that Zn, Fe, Cd, Cu, Ni, Mn Ca, and Mg are higher during autumn and K during winter. Enrichment Factors shows that Zn and Cd were highly enriched, Cu and Ni were moderately enriched, and Ca, K, and Mn were not enriched. Finally, backward trajectories for rural sites showed that only for Allende site a possible carry-over of pollutants is observed during the summer, since the wind currents come preferably from the northern part of the MAM.

Nanomechanical Insights into Versatile Polydopamine Wet Adhesive Interacting with Liquid-Infused and Solid Slippery Surfaces.

Mussel-inspired polydopamine (PDA) can be readily deposited on almost all kinds of substrates and possesses versatile wet adhesion. Meanwhile, slippery surfaces have attracted much attention for their self-cleaning capabilities. It remains unclear how the versatile PDA adhesive would interact with slippery surfaces. In this work, both liquid-infused poly(tetrafluoroethylene) (PTFE) (LI-PTFE) and solid slippery surfaces (i.e., self-assembly of small thiol-terminated organosilane, polysiloxane covalently attached to substrates) were fabricated to investigate their capability to prevent PDA deposition. It was found that PDA particles could be easily deposited on a PTFE membrane and the two types of solid slippery surfaces, which resulted in the alternation of their surface wettability and slippery behavior of water droplets. Adhesion was detected between a PDA-coated silica colloidal probe and the PTFE membrane or solid slippery surfaces through quantitative force measurements using an atomic force microscope (AFM), mainly due to van der Waals (vdW) and hydrophobic interactions, which led to the PDA deposition phenomenon. In contrast, LI-PTFE with a thin liquid lubricant film could effectively prevent PDA deposition, with negligible changes in surface morphology, wettability, and slippery characteristics. Although PDA particles could be loosely attached to the lubricant/water interface for LI-PTFE based on the capillary adhesion measured by AFM, they could be readily removed by gentle rinsing with water, as demonstrated by the ultralow friction over LI-PTFE as compared to PTFE using lateral force microscopy (LFM). Our results indicate that LI-PTFE possesses excellent antifouling and self-cleaning properties even when interacting with the versatile PDA wet adhesives. This work provides new insights into the deposition of PDA on slippery surfaces and their interaction mechanism at the nanoscale, with useful implications for the design and development of novel slippery surfaces.

Assessment of Potential Impacts of Peach Kernels and Cardoon as Co-Firing Fuels with Lignite Through Experiments on Reactivity and Ash Behavior

Objective : The reactivity and combustion performance of mixtures of lignite with peach kernel and cardoon were investigated, through thermal analysis experiments, for assessing the potential impacts of these wastes as co-firing fuels. Methods: Additionally, a control method was applied to reduce problematic elements from biomass ashes in order to mitigate deposition phenomena in co-firing units. The results showed that combustion performance of raw fuels followed the order cardoon>peach kernel>lignite, however in case of blends, this order was reversed lignite/peach kernel> lignite/cardoon, revealing synergistic effects between component fuels. Results: The combustion performance of lignite was improved by blending it with biomass fuels. Deposition problems should be expected in boilers firing peach kernel and cardoon fuels above 900°C. Conclusion: After alkalis leaching, the reactivity and efficiency of woody materials and mixtures with lignite were enhanced, while the slagging/fouling propensity was reduced.

HYGIENIC BASIS FOR MONITORING OF PMD

A rational criterion for the hygienic relevance of the surface area of dust settling in the lungs is formulated in the article. 
 The differential parameters of airborne dust are determined by measuring the mass concentration of particular matter PM10 and PM2.5. A unified model of the behavior of dust in the lungs has been developed. It describes the deposition of particles on the walls of the airways when cleaning the inhaled air and the subsequent removal of settled dust from the lungs. 
 The adequacy of the model was verified by the compliance with the results of in vivo testing. The phenomenon of dust deposition in the lungs is described. It is typical for periodic dust exposure in the workplace. Dust exposure is acceptable if the surface area of the deposited dust does not exceed the area of the internal surface of the airways. With this approach, the concentration of dust in inhaled air is recomputed into the surface area of dust particles deposited in the lungs. As the initial data, the results of routine measurements of the mass concentration of particulate matter PM10 and PM2.5 are used. Permissible concentration for PM10 close to the WHO Recommendations and adopted in industrialized countries. Permissible concentration for PM2.5 should be a lot stiffer than currently accepted. 
 In reality, only the pair PM10 and РМ2,5 gives a quantitative characteristic of the danger of dust exposure. It determines the entering to the area of permissible dust exposure.

Development of a SGJ-1 of Water-Based Anti-Wax Agent

The phenomenon of petroleum wax deposition is very common during oil well production. When the wax molecule condenses on the surface of the pipeline, it will hinder the exploitation of crude oil, reduce the recovery rate of crude oil, and may lead to the blockage of the pipeline when it is serious, so that the oil recovery work will stop. This phenomenon can be obviously changed by using wax cleaning agent. However, the low ignition point and toxicity of oil-based wax remover are not conducive to oil recovery. Therefore, a new water-based paraffin remover SGJ-1 was developed in this paper. The best formula is: wax dispersant 15%, wetting reversion agent 1%, sodium silicate 1%, alcohol cosolvent 8% and 75% water. Condensation point, wax dissolution rate and anti-wax performance of SGJ-1 water-based dewaxing and anti-waxing agent were tested by self-assembly testing device. The experimental results show that the condensation point of SGJ-1 is -34°C, the viscosity reduction effect is good under 35°C, and the wax dissolution rate is 0.0512 g/min, The highest wax prevention rate can reach 89.58% and the wax removal and wax prevention ability is excellent. Compared with other paraffin removers, SGJ-1 can also reduce the viscosity of crude oil, so it has a good development prospect.

Surface engineering of Rh-modified Pd nanocrystals by colloidal underpotential deposition for electrocatalytic methanol oxidation.

The development of methods to control the surface structures of metallic nanocatalysts is of vital importance for their application as heterogeneous catalysts in chemical conversions of energy and environmental and chemical engineering. The underpotential deposition (UPD) phenomenon has received considerable interest as a tool for the controllable synthesis of metal nanocrystals and engineering their catalytic performances. Herein, the discovery of UPD of Rh on Pd nanocrystals is reported. More importantly, the UPD of Rh is explored as a strategy to direct the synthesis of Rh-modified Pd nanocrystals with controllable shapes and surface structures. The mechanism of the UPD of Rh on Pd is elucidated in terms of electronegativity difference considerations. Compared with pristine Pd octahedral nanocrystals and commercial carbon-supported Pd catalysts, the Rh-modified Pd octahedral nanocrystals exhibit remarkable electrocatalytic performances during the methanol oxidation reaction in alkaline media. Our discovery heralds a new paradigm for UPD-mediated growth of metal nanocrystals and may provide a mechanistic understanding for the guided design of other colloidal UPD systems in the synthesis and surface engineering of metal nanocrystals.