Abstract
In this work, we attempt to determine the influence of the oxidation state of copper [Cu(I) vs Cu(II)], the nature of the interface (solid/aqueous vs solid/air), the incubation time, and the structure of N-substituted phenylboronic acids (PBAs) functionalizing the surface of copper oxide nanostructures (NSs) on the mode of adsorption. For this purpose, 4-[(N-anilino)(phosphono)-S-methyl]phenylboronic acid (1-PBA) and its two analogues (2-PBA and bis{1-PBA}) and the copper oxide NSs were synthesized in a surfactant-/ion-free solution via a synthetic route that allows controlling the size and morphology of NSs. The NSs were characterized by scanning electron microscopy, ultraviolet–visible spectroscopy, Raman spectroscopy, and X-ray diffraction, which confirmed the formation of spherical Cu2O nanoparticles (Cu2ONPs) with a size of 1.5 μm to 600 nm crystallized in a cubic cuprite structure and leaf-like CuO nanostructures (CuONSs) with dimensions of 80–180 nm in width and 400–700 nm in length and crystallized in a monoclinic structure. PBA analogues were deposited on the surface of the copper oxide NSs, and adsorption was investigated using surface-enhanced Raman spectroscopy (SERS). The changes in the orientation of the molecule relative to the substrate surface caused by the abovementioned factors were described, and the signal enhancement on the copper oxide NSs was determined. This is the first study using vibrational spectroscopy for these compounds.
Highlights
Arylboronic acids are a class of chemical compounds commonly used in modern synthesis to form C−C and Cheteroatom bonds.[1]
These acids exhibit a reversible coordination profile that is used as a tool for the construction of stimulus-dependent biconjugates used in pharmaceuticals, polymers,[3] organic synthesis, electrochemistry, catalysis,[4] materials chemistry, or separation processes.[6,7]
scanning electron microscopy (SEM) analysis of the bare copper(I) oxide NPs (Cu2ONPs) in Figure 2 (A−scale bar 10 μm and B−scale bar 1.5 μm) shows that the NPs have a spherical shape with a size of 1.5 μm to 600 nm
Summary
Arylboronic acids are a class of chemical compounds commonly used in modern synthesis to form C−C and Cheteroatom bonds.[1]. The use of PBA in the treatment of diabetes is based on their specific binding to 1,2-diols or polyols and the formation of reversible covalent PBA/diol complexes.[17] The formation of boronic acid esters is favored near or above the pKa of boronic acid. A similar conjugation is not as Received: November 9, 2021 Revised: December 8, 2021
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