Multi‐instrument characterization of the surfaces and materials in microfabricated, carbon nanotube‐templated thin layer chromatography plates. An analogy to ‘The Blind Men and the Elephant’

Abstract

We apply a suite of analytical tools to characterize materials created in the production of microfabricated thin layer chromatography plates. Techniques used include X-ray photoelectron spectroscopy (XPS), valence band spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS) in both positive and negative ion modes, Rutherford backscattering spectroscopy (RBS), and helium ion microscopy. Materials characterized include: the Si(100) substrate with native oxide: Si/SiO 2 , alumina (35 nm) deposited as a diffusion barrier on the Si/SiO 2 : Si/SiO 2 /Al 2 O 3 , iron (6 nm) thermally evaporated on the Al 2 O 3 : Si/SiO 2 /Al 2 O 3 /Fe, the iron film annealed in H 2 to make Fe catalyst nanoparticles: Si/SiO 2 /Al 2 O 3 /Fe(NP), and carbon nanotubes (CNTs) grown from the Fe nanoparticles: Si/SiO 2 /Al 2 O 3 /Fe(NP)/CNT. The Fe films and nanoparticles appear in an oxidized state. Some of the analyses of the CNTs/CNT forests appear to be unique: (i) the CNT forest appears to exhibit an interesting 'channeling' phenomenon by RBS, (ii) we observe an odd-even effect in the SIMS spectra of C n -species for n = 1 -6, with the n ≥ 6 ions showing a steady decrease in intensity, and (iii) valence band characterization of CNTs using X-radiation is reported. Initial analysis of the CNT forest by XPS shows that it is 100 at.% carbon. After one year, only ca. 0.25 at.% oxygen is observed. The information obtained from the combination of the different analytical tools provides a more complete understanding of our materials than a single technique, which is analogous to the story of 'The Blind Men and the Elephant'. The raw XPS and ToF-SIMS spectra from this study will be submitted to Surface Science Spectra for archiving.

Atomic layer deposition of aluminum-free silica onto patterned carbon nanotube forests in the preparation of microfabricated thin-layer chromatography plates

“…TLC plates were microfabricated using the methods described previously up through the growth of patterned CNT forests [11][12][13]30]. The mask used to make the plates in this study had zig-zag features that produced 3-µm wide hedges, 4.24-µm channel widths, and 50 µm channels as shown in Figure 1.…”

“…These include monolithic silica [1], glancing angle deposition (GLAD) [2][3][4], polymer monoliths [5][6][7][8], and electrospun polymers [9,10]. Our group has also been active in this area, reporting TLC plates with high efficiencies and short run times prepared from microfabricated, patterned, and infiltrated carbon nanotube (CNT) forests [11][12][13][14]. In general, these plates are prepared as follows.…”

“…It complicates the synthesis of the plates and limits their potential acceptance -normal phase (pure) silica is by far the most common TLC stationary phase. In addition to an exploration of different microfabrication schemes, we have reported the detailed characterization of the materials in our TLC plates [13,[25][26][27][28][29] and the effects of Fe layer thickness on nanoparticle size and CNT forest growth [30].…”

Chemical Separation on Silver Nanorods Surface Monitored by TOF-SIMS

“…This causes some inhomogeneity in separation zone leading to zone spreading. Some separation specific, nanotextured films, preparation methods have already been documented in the articles published by Linford research group [24][25][26][27]. In the next step various PDMS microfluidic channel designs based on hydrogel procedure preparation will be examined [28] followed by an integration of nanostructured functional films into miniaturized systems.…”

Изменение Химического Состояния И Концентрации Железа В Углеродных Нанотрубках, Полученных Методом CVD И Подвергнутых Импульсному Ионному Облучению

“…Элек-тронная микродифракция показала, что данные частицы состоят преимущественно из металлического железа (d = 2.1 nm). Однако также нельзя исключать наличия некоторого количества железа в соединении Fe 3 C. фицировать химическое состояние железа [22]. Так, для металлического железа значение данного параметра со-ставляет 13.2 eV, а для окисленного состояния железа - (O−Fe) [12,23,24].…”