Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

Publisher Summary The intensities of intraconfigurational f–f transitions are reviewed in the chapter The chapter presents the transition mechanisms for lanthanide ions—namely, the magnetic dipole transition, the induced electric dipole transition, and the electric quadrupole transition It discusses the way experimental intensities can be determined from the spectra The chapter also focuses on the expression of the dipole strength and the oscillator strength in oriented and in randomly-oriented systems Correction factors for lanthanide ions in a dielectric medium are described in the chapter Although only a few magnetic dipole transitions exist for the trivalent lanthanide ions, magnetic dipole transitions are of interest, because their intensities are in a first approximation independent of the ligand environment and can, thus, be used as intensity standards The intensity of a magnetic dipole transition can be calculated exactly, provided that suitable wavefunctions are available These wavefunctions can be obtained from diagonalization of the energy matrix

Chapter 167 Spectral intensities of f-f transitions

Transparent conducting oxides (TCOs) are electrical conductive materials with comparably low absorption of electromagnetic waves within the visible region of the spectrum. They are usually prepared with thin film technologies and used in opto-electrical apparatus such as solar cells, displays, opto-electrical interfaces and circuitries. Here, based on a modern database-system, aspects of up-to-date material selections and applications for transparent conducting oxides are sketched, and references for detailed information are given. As n-type TCOs are of special importance for thin film solar cell production, indium-tin oxide (ITO) and the reasonably priced aluminum-doped zinc oxide (ZnO:Al), are discussed with view on preparation, characterization and special occurrences. For completion, the recently frequently mentioned typical p-type delafossite TCOs are described as well, providing a variety of references, as a detailed discussion is not reasonable within an overview publication.

https://www.mdpi.com/1996-1944/5/4/661/pdf

Transparent Conducting Oxides—An Up-To-Date Overview

Nanokristalle sind von grundlegender Bedeutung in der modernen Wissenschaft und Technologie. Die Eigenschaften eines Nanokristalls lassen sich uber seine Form beeinflussen und auf eine bestimmte Anwendung hin zuschneiden. Ziel dieses Aufsatzes ist es, einen umfassenden Uberblick uber den aktuellen Stand der Forschung auf dem Gebiet der formkontrollierten Synthese von Metallnanokristallen zu geben. Nach einer kurzen Einleitung uber die Prinzipien von Kristallkeimbildung und -wachstum diskutieren wir einzelne Arten von Nanokristallformen und betrachten verschiedene experimentelle Parameter, uber die die Keimbildung und das Wachstum von Metallnanokristallen in der Losungssynthese gezielt manipuliert werden kann. Wir erlautern diese Methoden anhand von Beispielen, wo zumindest ein Grundverstandnis fur die beobachtete Formkontrolle vorhanden ist. Schlieslich stellen wir Anwendungen vor, bei denen die Formkontrolle von Metallnanokristallen ein entscheidender Faktor ist, und beenden den Aufsatz mit einem personlichen Ausblick auf kunftig zu erwartende Entwicklungen auf diesem Gebiet.

Formkontrolle bei der Synthese von Metallnanokristallen: einfache Chemie, komplexe Physik?

Crystal chemistry and electrical properties of the delafossite structure

Photoluminescent properties of glasses of the Ag 2 O–ZnO–P 2 O 5 system are reported. The compositions of the glasses are limited by the polyphosphate and diphosphate domain of this system. The phosphate structural units of the network former are deduced from Raman spectra. A comparison with the luminescent properties of crystallized silver phosphates of similar composition allows identification of two different emitting centers: isolated Ag + , Ag + –Ag + pairs, and a third center resulting from an Ag + –Zn 2+ interaction. The introduction of 1 mol% SiO 2 or Al 2 O 3 in these glasses leads to precipitation of silver particles, whose dimensions range from nanometers to micrometers, and to the appearance of luminescent centers (Ag 2 ) + detected around the micrometer particles by optical microscopy. We assume that these centers are an intermediate stage during the process of silver precipitation.

Silver aggregates in photoluminescent phosphate glasses of the `Ag2O–ZnO–P2O5' system

Silver particles of several sizes can be dispersed in glasses of the `Ag 2 O–ZnO–P 2 O 5 ' system. By introducing a small proportion of SiO 2 or Al 2 O 3 micron-sized silver particles are obtained in low silver content glass compositions whereas nanometer-sized particles precipitate in silver rich glasses. The particle-glass composites exhibit the classical absorption plasmon band peaking about 430 nm. The thermal variation of the peak full-width at half-maximum (FWHM) as the annealing temperature of the glass increases is analyzed by the Mie theory and corresponds to an increase of the particle radii from 11 to 30 nm. In composite glasses containing micrometric silver particles, time resolved luminescence spectroscopy reveals the formation of a new emitting center (Ag 2 ) + located in the vicinity of the silver particles and which can be considered as an intermediate step between Ag + –Ag + pairs and silver metal in the process of silver precipitation.

Silver particles in glasses of the `Ag2O–ZnO–P2O5' system

Luminescent properties of delafossite-type oxides LaCuO2 and YCuO2

The study of sodium borate glasses over the compositional range 10–35 mol.% Na2O by using Pb2+, Eu3+ and Nd3+ as local sounds shows the existence of two possible situations depending on whether the Na2O content is lower or higher than about 25 mol.%. In the first composition range the simultaneous increase of optical basicity and of modifier ion site asymmetry implies rather a 2D-character of the network former. The properties of the glasses with high Na2O content involve more 3D-character for the former sublattice.

C. Parent

Papers

Silver aggregates in photoluminescent phosphate glasses of the `Ag2O–ZnO–P2O5' system

Silver particles in glasses of the `Ag2O–ZnO–P2O5' system

Luminescent properties of delafossite-type oxides LaCuO2 and YCuO2

A structural interpretation of the Pb2+, Eu3+ and Nd3+ optical spectra in doped sodium borate glasses

Crystal Structure of Na2ZnP2O7: Reinvestigation