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Direct synthesis of ultrasmall and stable magnetite nanoparticles coated with one single carbon layer for sensitive surface-enhanced Raman scattering
摘要： Ultrasmall spherical magnetite nanoparticles (Fe3O4 NPs) coated with one single carbon layer (Fe3O4@1C NPs) were directly synthesized by a simple, fast one-step hydrothermal reaction at low temperature (200℃). The as-synthesized Fe3O4@1C NPs were easily separated and purified from the resultant mixture, without the need for any additional energy input and chemicals. The as-purified Fe3O4@1C NPs not only displayed typical superparamagnetic behavior but also exhibited quite good long-term stability after being exposed to the open air under the room conditions for more than 2 months. Importantly, the long-term stored Fe3O4@1C NPs exhibited a highly sensitive surface-enhanced Raman spectroscopy (SERS) response toward Rhodamine-b (RdB) molecules with low concentration. The multifunctional and recyclable Fe3O4@1C NPs presented a prospective application for the selective enrichment and sensitive SERS detection of chemical and biomolecular assays.
关键词： coated with one single carbon layer (Fe3O4@1C NPs),Dehydration reaction,Saturation magnetization,Long-term stability,Magnetite nanoparticles (Fe3O4 NPs)
更新于2025-11-14 17:03:37
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Real-time laser induced chemical derivatizations of peptide N-Terminus for in-situ mass spectrometric sequencing at sub-picomole and nanosecond scale
摘要： Distinguishing b- and y-ions is essential to compute amino acid sequences from either N- or C-terminus in mass spectrometry. We described herein a solvent free and real time on-plate derivatization approach that can tag N-terminus of peptides at microliter level with p-chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde for matrix assisted laser desorption ionization mass spectrometry (MALDI MS). Less than 1 mL of sample solutions can be directly mixed with equal volumes of p-chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde and a-cyano-4-hydroxycinnamic acid (CHCA), a matrix compound to co-crystalize with analytes for efficient absorption of laser energy and peptide ionization. When the mixture spotted on the sample plate is irradiated with the 3rd harmonic (355 nm) of Nd3+:YAG laser pulses (3 ns width), N-terminal amine groups of peptides instantly react with carbonyl groups of chlorobenzaldehyde or 2-hydroxy-5-methylisophthalaldehyde. Resultant peptides carrying with on-plate formed azomethine group (-C]N-) are simultaneously protonated and isolated as precursor ions for subsequent collision-activated dissociation. The mass shift with unique Cl isotopic signature unambiguously distinguishes b ions from y ions and other ions. This method does not need extensive sample preparation and is useful for those samples with limited quantities down to sub-picomole level in sub-microliter volumes. The efficiency was demonstrated with synthetic peptides and tryptic peptides of model proteins. It was found that 2-hydroxy-5-methylisophthalaldehyde provides improved yield for peptides containing lysine residues. Unknown proteins of human saliva and bovine milk as well as phosphopeptides have been identified.
关键词： Mass spectrometric de novo sequencing,N-terminal tag,2-Hydroxy-5-Methylisophthalaldehyde,Chlorobenzaldehyde,Photo induced dehydration reaction
更新于2025-09-16 10:30:52