Rational surface modification of Mn3O4 nanoparticles to induce multiple photoluminescence and room temperature ferromagnetism

Abstract

Surface modification can have a significant influence on the materials behavior at the nanoscale and can lead to nanostructures with novel properties. Here, we demonstrate the surface modification induced multiple photoluminescence and room temperature ferromagnetic activation of Mn 3 O 4 nanoparticles (NPs). Employing a systematic variation of the ligands, their functional groups and the structural position of the functional groups, we have identified the necessary and sufficient structural requirements of the surface co-ordinating ligands, in order to induce unprecedented optical/magnetic responses from the NPs. Using a multitude of spectroscopic techniques, we have investigated the mechanism behind the emergence of the multiple photoluminescence (PL), and it is revealed that the presence of a a-hydroxy carboxylate moiety in the ligands is necessary to activate the Jahn-Teller (J-T) splitting of Mn 3+ ions on the NP surface and the corresponding d-d transitions along with the ligandto-metal charge transfer transitions (LMCT, associated with Mn 2+/3+ -ligand interactions) is the key factor. However, the presence of a carboxylate group on the surface coordinating ligands is sufficient to activate the room temperature ferromagnetism of the NPs. Moreover, it has been observed that the ligands that induced the smallest crystal field splitting energy (CFSE) resulted in the strongest ferromagnetic activation of the NPs. Finally, the functionalized material has been identified as an efficient catalyst for the photo-degradation of a model cationic organic dye. Apart from the fundamental scientific interest, these results represent a promising route for the rational design of Mn 3 O 4 NPs adaptable to diverse applications.

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“…The decrease in the photocatalytic activity as shown in Fig. 3b confirms that the mechanism is mainly through ROS [28]. The photocatalysis rate also decreases in the presence of Cu 2 þ which is a well-known scavenger of super oxides and photogenerated electrons [29,30].…”

Safe and Symptomatic Medicinal Use of Surface-Functionalized Mn 3 O 4 Nanoparticles for Hyperbilirubinemia Treatment in Mice

“…The absorbance maxima at around 290 and 429 , 526, 746 nm correspond to the high-energy ligandto-metal charge transfer transition involving citrateMn 4+ interaction and Jahn-Teller (J-T) distorted d-d transitions centered over Mn 3+ ions respectively [21,22]. The NPs are also found to be fluorescent under various excitation wavelengths as reported earlier [21].…”

“…In a series of earlier studies from this group, we have established that the charge state of Mn in the citrate-capped Mn 3 O 4 nanoparticles (C-Mn 3 O 4 nanoparticles [NPs]) is involved in selective catalysis of BR in absence of any photoactivation [21,22]. The mixed valence state of Mn (+2, +3 and +4) along with the functional groups on the surface coordinating ligands of Mn 3 O 4 NPs leads to the exceptional catalytic activity.…”

Ligand‐Induced Evolution of Intrinsic Fluorescence and Catalytic Activity from Cobalt Ferrite Nanoparticles

“…This phenomenon can be explained by ligand-field theory.A se vident from the FTIR study,a fter fluorescencem odification,t he interactions among carboxylate (COO À )a nd hydroxyl (OÀH) groups of tartrate and metal centers in the NPs becamee nhanced. The tartrate ligand,c ontaining both s-donor( À OH) and p-donor( À COO À ) functional groups, [16,21] favors the quenching of magnetic moments of Co 2 + /3 + or Fe 3 + ions on the surfaceo fT -CoFe 2 O 4 NPs, leadingtoad ecrease in the saturation magnetization. [22] The interface of catalysis and nanoscience has paved the way for green chemistry.I nt his regard, we were curious to know the catalytic efficiency of the T-CoFe 2 O 4 NPs in the degradationo fB R, the pigmentw hose elevated level indicates jaundice.…”