Abstract The outdoor deployment of solar nanofluids in practical solar photothermal conversion devices for prolonged periods of time has been an ongoing challenge. This is due to their exposure to intense solar radiation, elevated temperatures, thermal and solar cycling, and other rough operation conditions that compromise their dispersion and chemical stability. This work is an attempt to address this challenge in light of state-of-the-art advances in understanding, characterizing, and mitigating issues pertaining to the stability of solar nanofluids. We first defined the concept of nanofluids, along with their types and applications, merits and limitations, and preparation techniques. This was followed by presenting the basic physical principles that govern the interparticle interactions, clustering and deposition kinetics, and theories of colloidal stability for nanoparticles in aqueous environments. Building on a sound understanding of these necessary fundamentals, the destabilization factors and instability effects on solar nanofluids were systematically identified. A critical evaluation of the most recent stability characterization techniques and stabilization strategies for solar nanofluids was then provided. A coverage of selected state-of-the-art works in the literature that target the enhanced stability of solar nanofluids in different photothermal conversion processes based on the direct volumetric absorption of solar radiation was presented and comparatively evaluated. Finally, recommendations were drawn regarding current knowledge gaps and future research directions in order to overcome the stability limitations hindering the deployment of solar nanofluids in practical solar photothermal conversion applications.

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关于太阳能纳米流体的胶体和化学稳定性：从纳米级相互作用到最新进展

摘要 太阳能纳米流体在实际太阳能光热转换装置中长时间的户外部署一直是一个持续的挑战。这是由于它们暴露于强烈的太阳辐射、高温、热和太阳循环以及其他会损害其分散性和化学稳定性的恶劣操作条件。鉴于在理解、表征和减轻与太阳能纳米流体稳定性有关的问题方面的最新进展，这项工作是为了应对这一挑战。我们首先定义了纳米流体的概念，以及它们的类型和应用、优点和局限性以及制备技术。随后介绍了控制粒子间相互作用、聚类和沉积动力学的基本物理原理，水环境中纳米颗粒的胶体稳定性和胶体稳定性理论。基于对这些必要基本原理的充分理解，系统地确定了对太阳能纳米流体的不稳定因素和不稳定性影响。然后提供了对太阳能纳米流体的最新稳定性表征技术和稳定策略的批判性评估。介绍并比较评估了文献中选定的最先进作品，这些作品旨在基于太阳辐射的直接体积吸收，在不同光热转换过程中增强太阳能纳米流体的稳定性。最后，