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In this study, we demonstrate the colloidal synthesis of nearly monodisperse, sub-100-nm phase change material (PCM) nanobeads with an organic n-paraffin core and poly(methylmethacrylate) (PMMA) shell. PCM nanobeads are synthesized via emulsion polymerization using ammonium persulfate as an initiator and sodium dodecylbenzenesulfonate as a surfactant. The highly uniform n-paraffin/PMMA PCM nanobeads are sub-100 nm in size and exhibit superior colloidal stability. Furthermore, the n-paraffin/PMMA PCM nanobeads exhibit reversible phase transition behaviors during the n-paraffin melting and solidification processes. During the solidification process, multiple peaks with relatively reduced phase change temperatures are observed, which are related to the phase transition of n-paraffin in the confined structure of the PMMA nanobeads. The phase change temperatures are further tailored by changing the carbon length of n-paraffin while maintaining the size uniformity of the PCM nanobeads. Sub-100-nm-sized and nearly monodisperse PCM nanobeads can be potentially utilized in thermal energy storage and drug delivery because of their high colloidal stability and solution processability.

We present a single-step, room-temperature synthesis of fluorescent organosilica nanobeads (FOS NBs). The FOS NBs were synthesized under aqueous conditions using (3-aminopropyl)triethoxysilane (APTES) as the silicon source in the presence of l-ascorbic acid (L-AA). In the APTES/L-AA/water ternary phase, the hydrolysis and condensation reaction of APTES occurred under acidic conditions to form spherical FOS NBs with an average diameter of 426.8 nm. FOS NBs exhibit excellent colloidal stability in aqueous media. The formation of FOS NBs was complete within a 10 min reaction time, which indicates potential for large-scale mass-production synthesis of luminescent colloidal NBs. The FOS NBs exhibited blue photoluminescence (PL) under UV excitation in the absence of an additional high temperature calcination process or with the incorporation of any fluorophores. This phenomenon is attributed to the presence of carbon-containing defects, which act as luminescent centers formed by the reaction between amino groups in the APTES and l-ascorbic acid reductant. Finally, the results of a cytotoxicity test and cellular uptake experiments revealed that the FOS NBs showed potential as optical contrast agents for bioimaging. Graphical Abstract

to their high electrical conductivity. [4] Cu NCs are also applied as electrocatalysts to accelerate various reactions such as the methanol oxidation reaction (MOR) [5] and carbon dioxide reduction. [6,7] In addition, the free electrons in Cu NCs interact with radiating electromagnetic waves, resulting in the characteristic localized surface plasmonic resonance (LSPR). [8] As Cu is less expensive than other noble metals, Cu NCs are also utilized as templates for deposition of noble metals, such as gold, [9] silver, [10] palladium, [11] and platinum, [12,13] in the form of core-shell, [14] hollow, [15,16] and alloy [17] NCs; this strategy decreases the usage of expensive noble metals, while their catalytic and electronic properties are maintained or occasionally even enhanced. The physical and chemical properties of Cu NCs can also be precisely tailored by changing their size, shape, and composition. [18] For instance, Cu nanowires are utilized in the fabrication of transparent and flexible conducting electrodes owing to the formation of interconnected conducting networks with a low amount of Cu nanowires. [19] The size-and shape-dependent catalytic activities of Cu NCs in the reduction of carbon dioxide (CO 2 ) have also been reported. CO 2 is converted into hydrocarbons, formic acid, or alcohols, depending on the size and exposed facets of the Cu NCs. [20][21][22] In addition, as the LSPR of the Cu NCs depends on their size and shape, their optical responses can be tuned for sensing. [23] In this context, it is important to develop appropriate synthetic methods to precisely control the size and shape of Cu NCs for exploring and then exploiting their optical, electronics, and catalytic properties.To date, many methods have been developed for the synthesis of colloidal Cu NCs with controlled size, shape, and composition. For example, the solution-phase syntheses of Cu NCs and Cu nanowires have been accomplished using organic reducing agents. [24][25][26] In these reactions, Cu ions are directly reduced to zerovalent copper in the presence of ascorbic acid or glucose to grow Cu NCs. In addition, the seed-mediated growth of Cu NCs has also been conducted using metal seeds with different reduction potentials. Gold [27] or palladium [28,29] used as seeds for the overgrowth of Cu induce the formation of Cu nanorods, nanowires, and right bipyramidal structures. The synthesis of Cu NCs via the disproportionation reaction of Cu(I) has also In this paper, the N,N-dimethylformamide (DMF)-assisted shape evolution of highly uniform and shape-pure copper nanocrystals (Cu NCs) is presented for the first time. Colloidal Cu NCs are synthesized via the disproportionation reaction of copper (I) bromide in the presence of a non-polar solvent mixture. It is observed that the shape of Cu NCs is systematically controlled by the addition of different amounts of DMF to the reaction mixture in high-temperature reaction conditions while maintaining a high size uniformity and shape purity. With increasing amount of DMF in the reaction mixtu...