Abstract
Continuous gas-phase synthesis of nanoparticles is associated with rapid agglomeration, which can be a limiting factor for numerous applications. In this report, we challenge this paradigm by providing experimental evidence to support that gas-phase methods can be used to produce ultrapure non-agglomerated “singlet” nanoparticles having tunable sizes at room temperature. By controlling the temperature in the particle growth zone to guarantee complete coalescence of colliding entities, the size of singlets in principle can be regulated from that of single atoms to any desired value. We assess our results in the context of a simple analytical model to explore the dependence of singlet size on the operating conditions. Agreement of the model with experimental measurements shows that these methods can be effectively used for producing singlets that can be processed further by many alternative approaches. Combined with the capabilities of up-scaling and unlimited mixing that spark ablation enables, this study provides an easy-to-use concept for producing the key building blocks for low-cost industrial-scale nanofabrication of advanced materials.
Highlights
Commonly result in impurities on the synthesized engineering nanoparticles (ENPs) as well as in hazardous wastes
We provide a general concept of continuous gas-phase synthesis of ultrapure singlet particles ranging from single atoms to particles in the nanometre range
In order to exclusively produce singlet particles, the process must be controlled in a way that particle growth does not exceed the critical size, which in turn depends on the material of the particles and temperature[38,39], and is relatively insensitive to other process parameters
Summary
Commonly result in impurities on the synthesized ENPs as well as in hazardous wastes In contrast to these classical paths, dry gas-phase methods provide more versatile and more environmentally friendly alternatives[15], involving a very limited number of preparation steps, producing ENPs in a continuous manner, allowing for simple and continuous conditioning and deposition/immobilization, and generating very little wastes. The growth governed by particle-particle collisions can be considered to start from the atomic scale, and particle-particle collisional growth represents a valid model for the description of the size distribution evolution[30,32,33,34,35] Note that this simplification is only valid in the case of rapidly quenched vapours emitted from point sources. In contrast to other high temperature aerosol synthesis methods[28,38], this feature provides great flexibility in controlling the size of the resulting nanoparticles
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