Effects of Carbon Nanowalls (CNWs) Substrates on Soft Ionization of Low-Molecular-Weight Organic Compounds in Surface-Assisted Laser Desorption/Ionization Mass Spectrometry (SALDI-MS)

Abstract

Carbon nanowalls (CNWs), which are vertically oriented multi-layer graphene sheets, were employed in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) measurements to detect low-molecular-weight organic compounds. CNWs substrates with widely different wall-to-wall distances from 142 to 467 nm were synthesized using a radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD) system with nanosecond pulse biasing to a sample stage. When survival yield (SY) values of N-benzylpyridinium chloride (N-BP-Cl) were examined, which is commonly used to evaluate desorption/ionization efficiency, a narrower wall-to-wall distance presented a higher SY value. The highest SY value of 0.97 was realized at 4 mJ/cm2 for the highest-density CNWs with a wall-to-wall distance of 142 nm. The laser desorption/ionization effect of arginine, an amino acid, was also investigated. When CNWs with a narrower wall-to-wall distance were used, the signal-to-noise (SN) ratios of the arginine signals were increased, while the intensity ratios of fragment ions to arginine signals were suppressed. Therefore, the CNWs nanostructures are a powerful tool when used as a SALDI substrate for the highly efficient desorption/ionization of low-molecular-weight biomolecules.

Stable Field Electron Emission and Plasma Illumination from Boron and Nitrogen Co‐Doped Edge‐Rich Diamond‐Enhanced Carbon Nanowalls

“…The structure consists of sharp, highly conductive graphene edges supplied by a solid, diamond-rich bottom. The Raman and transmission electron microscopy studies reveal a hybrid nature of sp 3 -diamond and sp 2 -graphene in these nanowalls. The ab-initio calculations were carried out to support the experimental observations of diamond-graphene hybrid structure.…”

“…To investigate the various carbon phases in the D-ECNWs, the carbon K-edge EELS in TEM was carried out. Figure 4c shows the core-loss EELS spectrum of the D-ECNWs, which indicates that the D-ECNWs have both sp 3 -bonded carbon (i.e., diamond), signified by a rise at 289 eV (σ*-band) and a dip in the vicinity of 302 eV (second diamond gap), 31 and by a π*-band at 285 eV indicates sp 2 -bonded carbon. [32] To categorize between graphite and amorphous carbon phases, the plasmon-loss EELS measurements in TEM were also carried out.…”

“…This results in the growth of section (II) of the boron and nitrogen co-doped diamond-graphene section. The specific depth of the boron-doped diamond section (I) could also be ascribed to the fact that the nanodiamonds seeding the surface have limited influence on the re-nucleation process in the latter phases of the growth but contribute efficiently to the sp 3 -rich structure just at the initial stages of the growth.…”

“…The FEE mechanism is proposed based on the above observations as follows: as the sp 2 graphene phase increased the percolative conduction paths in the D-ECNWs, [37,38] the numerous sharp edges on the top of the nanowalls induced a fast electron transport rate, [7,9,[48][49][50][51][52] thus resulting in enhanced FEE characteristics namely, low E 0 , large β, and high J e values. Moreover, the presence of sp 3 -diamond grains assisted in achieving a high FEE lifetime stability of these nanowalls. The D-ECNW nanostructures with efficient FEE characteristics are suitable as a cathode material for microplasma-based cathodic devices, which will be discussed shortly.…”

“…Over the last few years, carbon nanowalls (CNW) [1][2][3] grown by chemical vapor deposition have gained great popularity mainly due to their high surface area and high field electron emission (FEE). Such CNWs are compared to graphene nanosheets, grown vertically to the substrate.…”