Utilization
of plasmonics as a driving tool for chemical transformation
triggering enables to achieve unprecedented results regarding photochemical
conversion efficiency and chemical selectivity regulation. In this
study, the bimetallic surface plasmon-polariton-supported grating
is proposed as an effective background for plasmon-induced hydrogenation
of alkynyl groups of absolute chemoselectivity. The periodical bimetallic
structure consists of spatially modulated gold layers, covered with
the nanometer-thick platinum layer. The alkyne bonds are covalently
attached to the surface of the catalytic system through covalent grafting
of the bimetallic surface with 4-ethynylbenzenediazonium tosylate,
with triple bonds separated from the platinum layer by the benzene
rings. The proposed bimetallic structure enables selective hydrogenation
of alkyne bonds to alkenyl or alkyl moieties using cyclohexene as
a hydrogen source. The selectivity of hydrogenation can be controlled
by changing the structure parameters, for example, the thickness of
the upper platinum layer.
Surface‐modified gold multibranched nanoparticles (AuMs) were prepared by simple chemical reduction of gold chloride aqueous solution followed by in situ modification by using water‐soluble arenediazonium tosylates with different functional organic groups. Chemical and morphological structures of the prepared nanoparticles were examined by using transmission electron and scanning electron microscopies. The covalent grafting of organic compounds was confirmed by scanning electron microscopy with energy dispersive X‐ray spectroscopy (SEM‐EDX) and Raman spectroscopy techniques. Covalent functionalization of nanoparticles significantly expands the range of their potential uses under physiological conditions, compared with traditional non‐covalent or thiol‐based approaches. The antibacterial effect of the surface‐modified AuMs was evaluated by using Escherichia coli and Staphylococcus epidermidis bacteria under IR light illumination and without external triggering. Strong plasmon resonance on the AuMs cups leads to significant reduction of the light power needed kill bacteria under the mild conditions of continuous illumination. The effect of the surface‐modified AuMs on the light‐induced antibacterial activities was founded to be dependent on the grafted organic functional groups.
The circularly polarized light sensitive materials response can be reached at plasmon wavelengths through the coupling of intrinsically non-chiral plasmonic nanostructure with chiral organic molecules. As a plasmonic background, the different types of metal nanoparticles of various shapes and sizes are successfully tested and an apparent circular dichroism (CD) signal is measured in both, nanoparticles suspensions and after nanoparticle immobilization in substrate. In this work, the creation of plasmon-active 2D flakes of MXenes (Ti 3 C 2 T x ) is proposed, with the apparent CD response at plasmon wavelength, through the coupling of intrinsically non-chiral flakes with helically shaped helicene enantiomers. This work provides the first demonstration of chiral and plasmon-active 2D material, which shows the absorption sensitive to light intrinsic circular polarization even in plasmon wavelengths range. The appearance of the induced CD signal is additionally confirmed by several theoretical calculations. After the experimental and theoretical confirmation of the optical chirality at plasmon wavelengths, the flakes are utilized for the polarization sensitive conversion of light to heat, as well as for polarization dependent triggering of plasmon-assisted chemical transformation.
The family of MAX phases and their derivative MXenes are continuously growing in terms of both crystalline and composition varieties. MXenes are a new family of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides, with a general formula Mn+1AXn, where n = 1-3, M denotes a transition metal, A is an element such as aluminum or silicon, and X is either carbon or nitrogen. Considering the various elemental composition possibilities, surface functional tunability, various magnetic orders, and large spin-orbit coupling, MXene can truly be considered as multifunctional materials that can be used to realize highly correlated phenomena. However, a change in surface chemical groups can significantly alter the properties and functionality of MXene flakes and may even damage the flakes. In this paper, we propose the possibility of using soft, chemical transformation to tune the MXene surface chemistry and termination. We used fluorinated and brominated substituents for MXenes grafting and subsequent analysis of the surface composition of the MXene flakes indicated a decrease in oxygen and a simultaneous increase in fluorine and bromine surface concentrations. The ability to graft organic groups with various substituents to the surface of the flakes opens up new possibilities for their application. The presence of fluorinated groups on the surface makes it hydrophobic, which allows the creation of water-repellent flakes, and prevents rapid oxidation by atmospheric oxygen and related formation of titanium oxide on the surface.
In this contribution, we present the new approach for plasmon assisted grafting of anisotropic gold nanorods (AuNRs) with spatial selectivity, which was used for creation of nanoparticles with amphiphilic surface. The surface modification was carried out in two stages with implementation of: (I) the plasmon-activated iodonium salt (IS), and (II) the aryl diazonium salt (ADT). The plasmon assisted activation of IS was performed under the illumination of AuNRs with wavelength corresponded to the longitudinal plasmon resonance of AuNRs and resulted in grafting of organic moieties (Ar-(CF3)2) to AuNRs edges. The AuNRs lateral sides remains ungrafted and were further decorated with ADT-COOH. As result of varying substituents in the chemical structures of iodonium and diazonium salts the amphiphilic NPs with spatially divided hydrophobic (grafted to AuNRs edges) and hydrophilic (grafted to AuNRs lateral sides) chemical groups were obtained. Corresponded UV-Vis and Raman measurements confirm the success of AuNRs chemical grafting. As result, the AuNRs with spatially separated chemical moieties were created in very simple way, primarily in solution and without the need of sophisticated technique of NPs mobilization or their surface screening.
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