Tuning infrared plasmon resonances in doped metal-oxide nanocrystals through cation-exchange reactions

Abstract

Metal-oxide nanocrystals doped with aliovalent atoms can exhibit tunable infrared localized surface plasmon resonances (LSPRs). Yet, the range of dopant types and concentrations remains limited for many metal-oxide hosts, largely because of the difficulty in establishing reaction kinetics that favors dopant incorporation by using the co-thermolysis method. Here we develop cation-exchange reactions to introduce p-type dopants (Cu + , Ag + , etc.) into n-type metal-oxide nanocrystals, producing programmable LSPR redshifts due to dopant compensation. We further demonstrate that enhanced n-type doping can be realized via sequential cation-exchange reactions mediated by the Cu + ions. Cation-exchange transformations add a new dimension to the design of plasmonic nanocrystals, allowing preformed nanocrystals to be used as templates to create compositionally diverse nanocrystals with well-defined LSPR characteristics. The ability to tailor the doping profile postsynthetically opens the door to a multitude of opportunities to deepen our understanding of the relationship between local structure and LSPR properties.

Hydrogen‐Doping‐Induced Metal‐Like Ultrahigh Free‐Carrier Concentration in Metal‐Oxide Material for Giant and Tunable Plasmon Resonance

“…Localized surface plasmon resonance (LSPR), a collective freecarrier oscillation behavior initially found in noble metals, has fostered a topical field of plasmonics. [1][2][3] In recent years, many efforts have been devoted to converting non-metals, in particular semiconductors, into metal-like plasmonic materials [4] by introducing dopants [5,6] or defects. [7][8][9] Owing to the merits of low cost, tunable electronic structure, high chemical activity, the plasmonic response has also been demonstrated by surfaceenhanced Raman spectra (SERS) of rhodamine 6G molecules adsorbed on H x MoO 3 , which exhibits an enhancement factor of 1.1 × 10 7 with a detection limit at a concentration as low as 1 × 10 −9 mol L −1 , representing the best among the hitherto reported metal oxides.…”

Modified Absorption and Emission Properties Leading to Intriguing Applications in Plasmonic–Excitonic Nanostructures

“…tracked the growth of Cu:ICO (indium doped CdO) nanocrystals using XPS studies, presented in Figure 7c. [ 136 ] XPS scan confirms the presence of Cu + and absence of Cu(0), which certify the rapid conversion of Cu 2+ to Cu + (within 30 s). Also, after 1 h the peak in rectangular region starts to stir up which shows presence of Cu 2+ feature.…”

Biologically interfaced nanoplasmonic sensors

“…There is also increasing demand to explore new surface chemistries to cater emerging plasmon-active materials such as aluminium, [86][87][88] copper, 89,90 graphene 91-93 and highly-doped semiconductor nanocrystals. [94][95][96] Along this line, the INPS conguration would be advantageous in conferring chemical stability, especially to materials that are reactive or prone to oxidation such as aluminium and copper. 87,90 Conversely, the rapid formation of native oxides necessitates the INPS overcoating step to be performed as part of overall nanostructure fabrication process to ensure that conformal overlayers can be attained controllably on new materials without the formation of undesired intermediate oxide layers.…”