Synthesis and Study of Organic Nanostructures Fabricated by Inclusion of 2-Methylbenzimidazole Molecules in Nanotubes of Chrysotile Asbestos, Mesoporous Silica, and Nanopores of Borate Glasses

Our plain-English summary of Synthesis and Study of Organic Nanostructures Fabricated by Inclusion of 2-Methylbenzimidazole Molecules in Nanotubes of Chrysotile Asbestos, Mesoporous Silica, and Nanopores of Borate Glasses, by E. Balashova, A.A. Levin, S. Pavlov, et al (International Journal of Molecular Sciences, 2023).

The study

• Authors: E. Balashova, A.A. Levin, S. Pavlov, A. Starukhin, A. Fokin, D. Kurdyukov, D. Eurov, B. Krichevtsov
• Journal: International Journal of Molecular Sciences
• Published: 2023;24(18)
• Read it: PubMed · Publisher · Free full text

Abstract

New organic nanostructures were synthesized by introducing 2-methylbenzimidazole (MBI) molecules from a melt, gas phase, or alcoholic solution into nanosized voids of borate porous glasses (PG), nanotubes of chrysotile asbestos (ChA), and mesoporous silica (MS). The incorporation of MBI into borate glasses with different pore sizes is accompanied by the appearance of several phases formed by nanocrystallites which have a MBI crystal structure, but somewhat differ in lattice parameters. The size of some crystallites significantly exceeds the size of nanopores, which indicates the presence of long-scale correlations of the crystal structure. The size of MBI nanocrystallites in ChA was close to the diameter of nanotubes (D ~10 nm), which shows the absence of crystal structure correlations. The XRD pattern of mesoporous silica filled by MBI does not exhibit reflections caused by MBI and a presence of MBI was confirmed only by the analysis of correlation function. The incorporation of MBI molecules into matrices is observed through optical IR absorption spectroscopy (FTIR) and photoluminescence. Introducing MBI in ChA and MS is followed by the appearance of bright green photoluminescence, the spectral structure of which is analogous to MBI crystals but slightly shifted in the blue region, probably due to a quantum-size effect. The influence of MBI inclusion in PG and ChA on the permittivity, dielectric losses, conductivity, and parameters of their hopping conductivity is analyzed.

In plain English

This laboratory materials-science study from Saint Petersburg, Russia, did not examine people, animals or health effects. The authors filled the tiny voids of three materials with molecules of an organic compound, 2-methylbenzimidazole (MBI): porous borate glasses (pores about 2.5, 7 and 30 nm), natural chrysotile asbestos (hollow tubes about 9 nm wide) and mesoporous silica (pores about 3 nm). They used X-ray diffraction, infrared spectroscopy and photoluminescence (light-emission) measurements, plus electrical measurements on the filled glasses and asbestos. In chrysotile, MBI formed two crystal phases whose crystals were close to the tube width. Infrared spectra showed MBI present in the filled asbestos sample. Under a 405 nm laser, unfilled chrysotile gave practically no light, while filled chrysotile gave quite bright light. At 100 Hz, filled chrysotile had about half the electrical permittivity and dielectric loss of empty chrysotile. The authors linked the higher values in empty tubes to water adsorbed from the air. In the glasses, some MBI crystals were much larger than the pores. The authors concluded that MBI easily entered all three materials and that the glowing nanostructures are promising materials for medical biosensors.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory materials-science study: synthesis and physical characterization of nanocomposites by X-ray diffraction, infrared absorption and photoluminescence, with dielectric measurements on the glass and asbestos samples. No human or animal subjects.
• Who was studied: Material samples studied at the Ioffe Institute, Saint Petersburg, Russia: Vycor porous borate glasses with pores of about 2.5, 7 and 30 nm; natural chrysotile asbestos with a tube diameter of about 9 nm (a plate and a milled powder); and mesoporous silica particles with pores of about 3 nm.
• Exposure: Not a human exposure. The matrices were filled with the organic compound 2-methylbenzimidazole (MBI). The glasses and chrysotile were filled from an MBI melt (glasses also from the gas phase), and the silica from an alcohol solution of MBI.
• Main results:
  • In chrysotile asbestos (both the plate and the milled powder), MBI formed two crystal phases whose crystallite sizes were close to about 9 nm, the tube diameter.
  • No larger or smaller MBI crystallites were found in chrysotile. The authors interpreted this as no linking of MBI crystal structure between different asbestos tubes.
  • In the borate glasses, some MBI crystallites were much larger than the pores: about 100 nm and 15 nm in the 2.5 nm-pore glass, and about 60, 30 and 18 nm in the 7 nm-pore glass.
  • In the mesoporous silica, X-ray patterns showed no reflections from MBI or any other phase.
  • Infrared absorption spectra showed MBI molecules present in the MBI-filled chrysotile sample.
  • Photoluminescence was excited with a 405 nm laser. Unfilled chrysotile was practically non-luminous at room temperature. After MBI was introduced, the chrysotile showed quite bright photoluminescence, with bands shifted to shorter wavelengths by about 16 meV compared with bulk MBI crystals.
  • At 100 Hz, the effective permittivity and dielectric loss of MBI-filled chrysotile were almost two times smaller than in empty chrysotile.
  • The authors associated the large low-frequency values in empty chrysotile with water molecules adsorbed in the nanotubes from the air.
  • From the hopping-conductivity analysis, the energy barrier was about 2.58 eV in MBI-filled chrysotile versus about 0.77 eV in unfilled chrysotile.
• The authors' conclusion: The authors concluded that MBI molecules easily penetrate borate glass nanopores, chrysotile asbestos nanotubes and mesoporous silica without external pressure. They also concluded that the bright luminescence of these nanostructures makes them promising materials for medical biosensors.
• Limitations the authors state:
  • Infrared absorption from MBI could not be observed in the glass and silica samples, because the matrices themselves absorbed too strongly.
  • The silica pores were filled to a lower degree than the glass and asbestos.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Crystal Structure.

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