Photochemical Synthesis and Multiphoton Luminescence of Monodisperse Silver Nanocrystals

Abstract

A rapid, photochemical solution-phase synthesis has been developed for the production of monodisperse, nanometer-sized silver particles. The stabilizer used in the synthesis can be used to control the average diameter of the particles over a range from 1 to 7 nm. The same reaction mixture can also be employed to deposit patterns of nanoparticles with a laser via multiphoton absorption. The particles exhibit strong multiphoton absorption-induced luminescence when irradiated with 800-nm light, allowing emission from single nanoparticles to be observed readily.Keywords Silver nanoparticle . Photochemical synthesis . Multiphoton absorption . LuminescenceApplications of noble-metal nanoparticles have grown exponentially over the past decade. Silver is one of the least expensive of the noble metals and is only weakly reactive in the bulk. In nanoparticle form, silver has properties that can be exploited for applications such as surface-enhanced Raman spectroscopy (SERS) [1], even down to the single-molecule level [2,3]. In addition, subnanometer silver clusters show considerable promise as luminescent media for single-molecule studies [4,5]. Although the preparation of monodisperse nanoclusters of metals such as gold and platinum with average diameters that can be less than 1 nm is well documented [6,7], the synthesis of monodisperse silver nanoclusters is generally a considerably more difficult prospect, and it has been difficult to attain diameters of less than 3 nm in solution [8,9]. Here we report a facile solution-phase photochemical synthesis that, in a matter of minutes, produces monodisperse silver nanoclusters with controllable average diameters that can range from 1 to 7 nm. We further show that two-photon absorption (TPA) can be used to pattern the nanoparticles on a substrate. In addition, the particles exhibit strong multiphoton-absorption-induced luminescence (MAIL) upon irradiation with ultrafast pulses of 800-nm light, allowing the emission of individual particles to be monitored.The role of kinetics in determining the average size and dispersity of semiconductor nanoparticles has long been recognized and used to advantage [10]. Many such schemes require the rapid mixing of precursors to initiate the synthesis of nanoparticles. However, this type of strategy has received considerably less attention in the synthesis of noble-metal nanoparticles. A key element in such an approach is the ability to reduce silver cations quickly, such that nanoparticles with small diameters can be trapped kinetically. Photochemical reduction is an attractive means of accomplishing this end, as it allows for complete mixing of the reagents before the synthesis is initiated. Whereas a number of groups have reported photochemical syntheses of silver nanoparticles [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], in all of this previous work, the resultant nanoparticles have been polydisperse and often relatively large as well. The polydispersity of the particles produced is probably related to the fact that the...

Multiphoton Fabrication

“…[111] We have also reported the deposition of silver nanoparticles from a solution of silver perchlorate by using a photoreducing agent. [112] Similarly, Kawata and coworkers have demonstrated the fabrication of 2D and 3D patterns of silver and 2D patterns of gold from aqueous solutions of AgNO 3 and HAuCl 4 , respectively. [113,114] In all instances the patterns are granular, but in some cases they still show good electrical conductivity.…”

Strong Near-infrared Avalanche Photoluminescence from Ag Nanowire Arrays

“…Photoactivation and visible PL from Ag nanoparticles with diameters of several nanometers induced by one-photon and two-photon absorptions were also reported [18][19][20][21]. The surface-enhanced Raman scattering (SERS) from the Ag NW arrays with large NW diameter (d NW ∼100 nm) was extensively studied [22][23][24][25][26].…”

Mehrphotonen‐Mikrofabrikation

“…Wir haben auch die Abscheidung von Silbernanopartikeln aus einer Silberperchloratlösung mithilfe eines photochemischen Reduktionsmittels beschrieben. [112] Auf ähnliche Weise erzeugten Tanaka, Kawata und Mitarbeiter zwei-und dreidimensionale Silber-und zweidimensionale Goldstrukturen aus wässrigen [118] Wir haben diese Arbeit über die Herstellung von zweidimensionalen Silberstrukturen erweitert, indem wir zeigten, dass man eine stromlose Anreicherung mit Kupfer dazu einsetzen kann, die Silberstrukturen leitfähig zu machen. [119] Die Leitfähigkeit war anschließend nur noch um den Faktor vier geringer als für das makroskopische Metall.…”