Selective Enhancement of Photoluminescence in Filled Single‐Walled Carbon Nanotubes

Abstract

The insertion of organometallic molecules into the hollow core of singlewalled carbon nanotubes can drastically change their properties. Using biocompatible standardized suspensions of pristine, opened, and fi lled nanotubes, a very selective enhancement of the photoluminescence and optical absorption is observed. Via ferrocene encapsulation, the PL signal increases almost by a factor of three for tubes with chiralities such as (8,6) and (9,5). This behavior is attributed to a local electron charge transfer from the ferrocene molecules that balances out the p-type doping of the nanotubes resulting from the modifi ed charge distribution of the surfactant molecules and the opening process. The near infrared photoluminescence of the nanotubes in solution is strongly enhanced when ferrocene is encapsulated. The diameter-dependent charge transfer is additionally confi rmed by fi rst principles calculations. These fi ndings highlight an essential ingredient to optimize the application of solvated nanotubes, for instance, as in-vivo near infrared sensors in biomedical research.

Selective Enhancement of Inner Tube Photoluminescence in Filled Double‐Walled Carbon Nanotubes

“…[ 20 ] On the other hand, the charge transfer already starts causing this deviation in the Raman frequency from the vacuum case for chains containing around 20 carbon atoms. Therefore, the stronger enhancement in absorption features caused by shorter chains rather than the longest ones bears a striking resemblance to the enhancement of absorption features (and photoluminescence intensity) found for SWCNT fi lled with ferrocene: [ 18 ] There, the best enhancement was attributed to an optimum value for the n-type doping of the SWCNT by the ferrocene molecule, cancelling out the p-type doping from the opening process and the surfactant molecules. In our case, an optimum value for the charge transfer from the inner tube to the carbon chain given by the chain length has a similar effect, nullifying the outer tubes charge transfer to the inner tube.…”

“…Normalization of the different suspensions with respect to their optical density was achieved by taking the minimum between the fi rst and second optical transition of the inner tubes. [ 14,18 ] …”

Advances in tailoring the electronic properties of single-walled carbon nanotubes

“…According to the data presented in reports on the experimental and theoretical investigations of the electronic properties of filled SWCNTs, the following substances have an electron donor effect on the nanotubes: molecules -organic molecules (tetrakis(dimethylamino)ethylene (TDAE) and tetrathiafulvalene (TTF) [48,356]) and organometallic molecules (Co(C 5 H 5 ) 2 , Co(C 5 H 4 C 2 H 5 ) 2 [47,399,400], Fe(C 5 H 5 ) 2 [50,260,262,263,265,267,399,400], Ce(C 5 H 5 ) 3 [51,269], M(C 5 H 5 ) 2 , M= V, Cr, Mn, Ni [399]) and simple substances -metals (Ag [46,293,294,296,315,365,401], Cu [293,295], Eu [272,402], Li, K [403], Ti, Zn, Co, Ni, Fe, Mo, Gd, Cu [402,[404][405][406][407][408][409][410]). …”

“…The filling of the nanotubes with organic molecules (TDAE, TTF [48,356]) and organometallic molecules (Co(C 5 H 5 ) 2 , Co(C 5 H 4 C 2 H 5 ) 2 112 [47], Fe(C 5 H 5 ) 2 [50,260,262,263,265,267], Ce(C 5 H 5 ) 3 [51,269]) was performed via the gas phase method (see section 5.2.2), which resulted in clean samples suitable for further spectroscopic investigations. It should be noted that it was also reported that the incorporation of ferrocene Fe(C 5 H 5 ) 2 into the nanotubes can be performed by the liquid phase method using its solution in an organic solvent [284].…”

Nanowires sheathed inside nanotubes: Manipulation, properties and applications

“…of nanotubes filled with foreign materials. Recent in-depth study has revealed more applications for these 1D nanomaterials of nanowires sheathed inside nanotubes [76,[135][136][137][138]. However, a systematic review on manipulation, property analysis and potential applications of these inorganic nanowires filled nanotubes using the in-situ HRTEM techniques has not yet been presented.…”