UV-Vis-NIR Laser Desorption/Ionization of Synthetic Polymers Assisted by Gold Nanospheres, Nanorods and Nanostars

Abstract

The laser desorption/ionization (LDI) assisted by gold nanospheres, nanorods and nanostars has been investigated. Laser fluence thresholds for the appearance of cationized adducts of a polydispersed polyether standard (polyethylenglycol PEG600) have been determined at the near ultraviolet-visible-near infrared wavelengths delivered by a Nd:YAG laser (266, 355, 532, 1,064 nm). The results demonstrate the efficiency of surface plasmon excitation to assist laser desorption/ionizaton at laser wavelengths extending to the visible and near infrared, with advantages with respect to conventional LDI techniques using ultraviolet wavelengths. A close correlation is found between the optical absorbance of the nanoparticles and the LDI thresholds, although for the nanospheres plasmonic excitation in the visible appears to be more efficient than non-plasmonic excitation at shorter UV wavelengths. The recorded molecular weight distributions for the PEG600 standard show that the LDI process tends to be less efficient for the heavier components of the polymer mixture, presumably as a consequence of their stronger bonding to the nanoparticle substrate. The role of the coating agent of the nanoparticles in the observed LDI behavior is discussed.

Functionalized Nanoparticles and Nanostructured Surfaces for Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

“…84 Gámez et al investigated SALDI-MS with Au nanospheres, nanorods, and nanostars at four wavelengths covering the UV, visible, and near-infrared ranges. 85 A close correlation was found between the plasmonic excitation of the NPs and the LDI thresholds.…”

SERS Nanosensors and Nanoreporters: Golden Opportunities in Biomedical Applications

“…When nanoparticles are irradiated with laser energy, the PPTT property successfully transduces photon energy into heat surrounding each nanoparticle that leads to cell damage and cancer cell killing . Using NSs for photothermal cancer therapy was first mentioned in the literature by Gámez et al Later, Lu et al and Yuan et al applied star‐shaped nanoparticles to PTT for the first time in vitro and in vivo , respectively . Using TAT‐peptide functionalized NSs, our group achieved photothermolysis under 0.2 W cm −1 , which is the lowest irradiance ever reported for use in PPTT .…”

Mechanisms of Nanophase-Induced Desorption in LDI-MS. A Short Review

“…In particular, the role of different shapes (spheres, rods, and stars) of AuNPs [75] as well as the role of morphology of Pd [79] (Figure 9) and Pt nanostructured materials [87,88] were investigated. Several groups also carried out similar works on Si-based materials [81,82,89].…”

“…Besides the importance of NP size [ 59 , 72 ] and composition [ 60 ], discussed in the previous section, other factors have been reported to influence the LDI process. Since the early appearance of nanostructures for MS applications, it was shown that surface plasmon (SP) excitation could enhance both the electromagnetic field and the charge transfer between the NP and the adsorbate molecules [ 73 ], thus affecting both desorption and ionization phenomena [ 59 , 74 , 75 ]. Such correlation was deeply studied for gold nanostructures, demonstrating that a visible laser at 532 nm, which can be resonantly absorbed by AuNPs (SP band falling in the 500 nm–600 nm range), positively affects analyte detection [ 74 , 75 , 76 , 77 ], provided that no aggregation phenomena occur.…”

“…Since the early appearance of nanostructures for MS applications, it was shown that surface plasmon (SP) excitation could enhance both the electromagnetic field and the charge transfer between the NP and the adsorbate molecules [ 73 ], thus affecting both desorption and ionization phenomena [ 59 , 74 , 75 ]. Such correlation was deeply studied for gold nanostructures, demonstrating that a visible laser at 532 nm, which can be resonantly absorbed by AuNPs (SP band falling in the 500 nm–600 nm range), positively affects analyte detection [ 74 , 75 , 76 , 77 ], provided that no aggregation phenomena occur. Interestingly, AuNP absorption associated to broad interband in the UV region may also promote the LDI process through thermionic emission of electrons by interband excitation when a UV laser is used [ 59 ].…”