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

Wei

Colloids and Surfaces A: Physicochemical and Engineering Aspect

et al. 2015

h i g h l i g h t s• A simple sensitive colorimetric sensing platform for Cr (III) and Cr (VI) detection.• The strategy relied on Cr (III)-citrate chelation inducing aggregation of Au NPs.• Cr (VI) ion was reduced to Cr (III) by ascorbic acid.• The strategy provided potential for heavy metal speciation analysis. In this work, a simple "red-to-blue" colorimetric method for highly sensitive and selective determination of Cr (III) and Cr (VI) was presented, which was based on the aggregation of Tween 20-stabilized gold nanoparticles (Tween 20-Au NPs). This strategy relied upon the distance-dependent optical properties of gold nanoparticles (Au NPs), strong chelating between Cr (III) and citrate, and the reduction of Cr (VI) to Cr (III) by ascorbic acid (AA). Cr (III) could chelate with citrate to form a stable Cr (III)-citrate complex and thereby induce the aggregation of Tween 20-Au NPs. Thus, the sensing of Cr (III) and Cr (VI) based on aggregation of Au NPs was developed with the color of the Au NPs changing from red to blue, which was readily seen by the naked eye. The color change and surface plasmon resonance (SPR) absorption were used to monitor Cr (III) and Cr (VI) levels. Under the optimal assay conditions, good linear relationship was obtained, and the detection limit of Cr (III) and Cr (VI) were 0.016 M and 0.009 M in standard aqueous solution, respectively. Furthermore, the colorimetric method exhibited a good selectivity over other metal ions and was successfully applied to detect Cr (III) and Cr (VI) in real water samples.

Section: Introductionmentioning

confidence: 99%

Red-to-blue colorimetric detection of chromium via Cr (III)-citrate chelating based on Tween 20-stabilized gold nanoparticles

Wei

Colloids and Surfaces A: Physicochemical and Engineering Aspect

et al. 2015

“…Surface-assisted laser desorption/ionisation mass spectrometry (SALDI-MS) is probably the most sensitive method of detecting residual CTAB on AuNRs, since quaternary ammonium ions have a strong capacity to be desorbed and ionised in LDI-MS. 24,25 The ionisation principle of SALDI is similar to that of matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS), [26][27][28] with the UV-absorbing organic matrix commonly used in MALDI replaced by UV-absorbing nanomaterials such as gold nanoparticles. 28 The organic matrix-free ionisation technique of SALDI-MS can avoid interference caused by organic matrix molecules in the low-mass region (below 500 Da).…”

Section: 2425mentioning

confidence: 99%

Effective removal of surface-bound cetyltrimethylammonium ions from thiol-monolayer-protected Au nanorods by treatment with dimethyl sulfoxide/citric acid

Nishida

Kawasaki

2017

RSC Adv.

Self Cite

Cetyltrimethylammonium bromide (CTAB)-based surfactants are typically used as morphology-directing/ stabilising agents for gold nanorods (AuNRs), forming bilayers on their surface. However, the biological applications of AuNRs require the removal of surface-bound CTAB due its high toxicity and the poor colloidal stability of CTAB-covered AuNRs in biological media. Herein, we report a simple and effective strategy for removing surface-bound cetyltrimethylammonium (CTA) cations from poly(ethylene glycol)thiolate-protected AuNRs (PEG-AuNRs) by treatment with dimethyl sulfoxide/citric acid (DMSO/Cit), achieving residual CTA ion levels that cannot be detected by highly sensitive mass spectrometry or X-ray photoelectron spectroscopy (XPS) techniques. The DMSO/Cit treatment is thought to destabilise the Ag-Br-CTA complex on AuNRs, since citric acid forms strongly bound chelate complexes with CTA cations.

J. Am. Soc. Mass Spectrom.

“…High molecular mass analysis with NP matrices has been particularly problematic [40,58]. The possible cause is that NPs are heavy and surface bound, and thus do not form an abundant matrix plume like organic matrices.…”

Section: Npca Maldi Ms Of High Mass Pdmsmentioning

confidence: 99%

“…Applications of NP matrices for synthetic polymer analysis are limited to a few classes in the <7000 m/z region [34]; for example, porous-silicon for polyesters and polymethyl methacrylate (PMMA) [35,36], ZnO for polyethylene glycol (PEG), polystyrene (PS), and PMMA [34], graphene for polypropylene glycol (PPG), PS, and PMMA [37], Au@SiO 2 NPs for PEG [38], and halloysite nanoclay for polyester and degradation products [39]. In part, this limited application of NP matrices in polymer analysis is because NP matrices have been less efficient in desorption/ionization of high molecular mass compounds [40], while polymers are often of medium to high molecular mass.…”

Section: Introductionmentioning

confidence: 99%

Citric Acid Capped Iron Oxide Nanoparticles as an Effective MALDI Matrix for Polymers

Liang

Sherwood

Macher

et al. 2016

Abstract. A new matrix-assisted laser desorption ionization (MALDI) mass spectrometry matrix is proposed for molecular mass determination of polymers. This matrix contains an iron oxide nanoparticle (NP) core with citric acid (CA) molecules covalently bound to the surface. With the assistance of additives, the particulate nature of NPs allows the matrix to mix uniformly with polar or nonpolar polymer layers and promotes ionization, which may simplify matrix selection and sample preparation procedures. Several distinctively different polymer classes (polyethyleneglycol (PEG), polywax/polyethylene, perfluoropolyether, and polydimethylsiloxane) are effectively detected by the water or methanol dispersed NPCA matrix with NaCl, NaOH, LiOH, or AgNO 3 as additives. Furtheremore, successful quantitative measurements of PEG1000 using polypropylene glycol 1000 as an internal standard are demonstrated.