The reduction of Ag + ions in N,N-dimethylformamide (DMF) is shown to take place spontaneously at room temperature. When no other additives are present in the system, the slow reduction leads to silver deposition on the glass walls of the container, while in the presence of 3-aminopropyltrimethoxysilane (APS) stable dispersions of silver nanoparticles are obtained. Even though the reduction can be performed at room temperature, higher temperatures markedly increase the reaction rate and improve the monodispersity of the colloid. The reduction rate and morphology of the colloidal particles also depend on the ratio [Ag]/[APS]. The reduction takes place both with nitrate and perchlorate as counterions, which confirms that DMF plays the role of a reducing agent. Additionally, when excess APS is used, a thin, homogeneous silica shell is formed on the silver particle surface.One of the main applications of metal nanoparticles is found in catalysis. 1,2 Since most of the reactions to be catalyzed take place in organic solvents, it is desirable to design synthetic methods which lead to the stabilization of metal nanoparticles in such solvents. This can be accomplished through the reduction of the metallic salts or complexes "in situ", or by transfer of aqueous colloids into the organic phase, 3,4 normally after surface modification. 5-7 In both cases, the reduction can be driven by a chemical reducing agent, 8-11 an electron scavenger for the formation of radicals promoted by γ, 12 UV, 13 or ultrasound 14 irradiation, or a thermal method such as prolonged reflux. 15 N,N-Dimethylformamide (DMF) is one of the standard organic compounds used as a solvent for various processes, including the preparation of colloids 16-18 which usually contain metals in their composition. The oxidation of DMF has been studied with respect to the production of hydrogen from water-DMF mixtures 19 and even for the reduction of Ni(IV) to Ni(II) in alkaline medium. 20 These studies show that DMF can be an active reducing agent under suitable conditions. We show here the ability of DMF to reduce Ag + ions to the zerovalent metal, even at room temperature and in the absence of any external agent. Such a redox process should be taken into account when handling solutions of metal ions in DMF, because it can also be of importance for metals other than silver. Furthermore, by means of a silane coupling agent, 21 dispersions of silver nanoparticles can be prepared which remain stable for months. We have also observed that the relative amount of this coupling agent, as well as the temperature, influences noticeably both the reaction rate and the morphology of the colloids obtained. Experimental SectionMaterials. AgNO3, AgClO4, and 3-(aminopropyl)trimethoxysilane (APS) were purchased from Aldrich. N,N-Dimethylformamide (DMF) was Fluka (Pure grade). Ethyl alcohol was Scharlau (Pure Grade). All chemicals were used as received. For the preparation of aqueous solutions, Milli-Q deionized water (18 MΩ) was used.Particle Preparation. Simple addition of aqueous...

A single nanoplatform integrating laser-induced heat generation by gold nanoparticles and temperature sensing up to 2000 K via (Gd,Yb,Er)2 O3 nanorods is demonstrated, which presents considerable potential for nanoscale photonics and biomedicine. Blackbody emission is ascertained from the temperature increment with AuNP concentration, emission color coordinates as a function of the laser pump power, and Planck's law of blackbody radiation.

Colloidal metal‐halide perovskite nanocrystals (MHP NCs) are gaining significant attention for a wide range of optoelectronics applications owing to their exciting properties, such as defect tolerance, near‐unity photoluminescence quantum yield, and tunable emission across the entire visible wavelength range. Although the optical properties of MHP NCs are easily tunable through their halide composition, they suffer from light‐induced halide phase segregation that limits their use in devices. However, MHPs can be synthesized in the form of colloidal nanoplatelets (NPls) with monolayer (ML)‐level thickness control, exhibiting strong quantum confinement effects, and thus enabling tunable emission across the entire visible wavelength range by controlling the thickness of bromide or iodide‐based lead‐halide perovskite NPls. In addition, the NPls exhibit narrow emission peaks, have high exciton binding energies, and a higher fraction of radiative recombination compared to their bulk counterparts, making them ideal candidates for applications in light‐emitting diodes (LEDs). This review discusses the state‐of‐the‐art in colloidal MHP NPls: synthetic routes, thickness‐controlled synthesis of both organic–inorganic hybrid and all‐inorganic MHP NPls, their linear and nonlinear optical properties (including charge‐carrier dynamics), and their performance in LEDs. Furthermore, the challenges associated with their thickness‐controlled synthesis, environmental and thermal stability, and their application in making efficient LEDs are discussed.

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