Graphene coated silica applied for high ionization matrix assisted laser desorption/ionization mass spectrometry: A novel approach for environmental and biomolecule analysis $ Hani Nasser Abdelhamid a,b , Bo-Sgum Wu a , Hui-Fen Wu a,c,d,e,f,n a Department of Chemistry, National Sun Yat-Sen University, Kaohsiung 804, Taiwan b Department of Chemistry, Assuit University, Assuit 71515, Egypt c College of Pharmacy, Kaohsiung Medical University, Kaohsiung 807, Taiwan d Center for Nanoscience and Nanotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan e Institute of Medical Science and Technology, National Sun Yat-Sen University, 80424 Taiwan f Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, Kaohsiung 804, Taiwan article info Article history: Received 23 January 2014 Received in revised form 7 March 2014 Accepted 10 March 2014 Available online 18 March 2014 Keywords: Graphene Silica Surface assisted laser desorption/ionization (SALDI) Surfactant abstract The integration of nanotechnology with mass spectrometry for sensitive and selective detection of molecules is a hot/important field of research. Synthesis of graphene (G) coated with mesoporous silica (SiO 2 , G@SiO 2 ) for mass spectrometric application has been demonstrated. For the first time, we proposed the significant role of surfactant that used during the synthesis of mesorporous silicate (SiO 2 ) in mass spectrometry. It was noticed that G could initiate SiO 2 via surfactants which work as initiators for further ionization. The porosity of SiO 2 trapped the analytes that was released and ionized with the surfactant fragments. Undoubtedly, strong background interferences were present in the case of organic matrix, which greatly obscured the detection of low molecular weight compounds. G@SiO 2 nanocomposite affords several advantages, such as the ability to detect small molecules ( o500 Da), high sample localization through silica mesoporosity, and high ionization efficiency over than G or conventional matrices. The high performance of G@SiO 2 is not only due to the large surface area but also due to high desorption/ionization efficiency of inevitably surfactant (cetyltrimethylam- monium chloride, CATB). Unlike the conventional MALDI-MS, the G@SiO 2 -MS is capable of generating multiply charged polysaccharides. The present method was validated to detect surfactants with low limits of detection. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Matrix-assisted laser desorption ionization mass spectrometry (MALDI–MS) is a soft ionization technique which could be applied for non-volatile molecule analysis [1]. However, it is difficult to detect low molecular weight (LMW) compounds (MWo1000 Da), because common MALDI matrices which are typically from low molecular weight organics acids produce matrix-related ions which show strong interferences at low mass regions (MWo1000 Da) [2,3]. Therefore, nanomaterials are attractive matrix subjects in MALDI-MS because of their promising features in applications and less interference. Various nanomaterials have been successfully applied in surface assisted laser desorption/ionization mass spectrometry (SALDI-MS) [4–10]. Com- mercial silylated silicon nanowires was used in laser desorption mass spectrometry (LDI-MS) and called as nano-assisted laser desorption/ ionization (NALDI-MS [11]. Polymer-assisted laser desorption/ioniza- tion mass spectrometry (PALDI-MS), based on small polymers as nonpolar matrices, was proposed [12]. A type of LDI-MS using sol– gel as matrix, called sol–gel-assisted laser desorption/ionization (SGALDI) mass spectrometry was also reported [13]. It is important to note that direct laser desorption/ionization (matrix-free) from various surfaces have been applied extensively [14,15]. Recently, matrix surfactant-suppressed laser desorption/ionization (MSLDI-MS [16] was successfully employed in the analysis of small molecules via the addition of cetyltrimethylammonium bromide (CTAB) which can suppress ions of the conventional matrix. Graphene (G) is truly the material of the moment since 2004 [17]. It is composed from a single layer of carbon atoms (sp 2 –sp 2 ) that can be prepared from graphite [17]. Thus, G was utilized as MALDI matrix to detect low-mass molecules, such as amino acids, polyamines, peptides, steroids, nucleosides, nucleotides, metals and metallodrugs [18–24]. The analytical application of G was reviewed [25]. Soft- landing using MALDI-MS (bottom–up growth) of polycrystalline layered ultrathin films to produce ultrapure ordered architectures of giant G nanosheet was reported [26]. Recently, G was used as a template to control the microstructure of mesoporous silica (SiO 2 ) Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta http://dx.doi.org/10.1016/j.talanta.2014.03.016 0039-9140/& 2014 Elsevier B.V. All rights reserved. ☆ Contract/grant sponsor: National Science Council Taiwan n Corresponding author at: Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, 804, Taiwan. Tel.: þ886 7525 2000 3955; fax: þ886 7525 3908. E-mail address: hwu@faculty.nsysu.edu.tw (H.-F. Wu). Talanta 126 (2014) 27–37