The
development of metal-free catalysts for hydrogenation reduction
of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) has been of great
increasing scientific and industrial importance. Herein, we reported
the preparation of sulfurized graphene (SG) nanomaterials by a well-developed
ball-milling method. The as-prepared SG nanomaterials were systematically
characterized by scanning electron microscope, transmission electron
microscope, Fourier transform infrared, and X-ray photoelectron spectroscopy.
The SG exhibited flake-like morphology with average size of 100 nm,
and the S doping (3.4 atom %) into the nanocarbon molecules results
in asymmetry of electron density distribution, providing high catalytic
performance for catalytic reduction of 4-NP to 4-AP by using NaBH4 as the reducer. The related catalytic mechanism and reaction
path of the reduction were investigated. The effects of different
initial 4-NP concentrations, initial reductant concentrations, catalyst
dosages, and reaction temperatures were presented, which have not
been reported so far. The thermodynamic parameters including activation
enthalpy and entropy were determined.
Fluorescent
carbon dots (FCDs) have received considerable attention
because of the great potential for a wide range of applications, from
bioimaging to optoelectronic devices. In this work, we reported the
synthesis of nitrogen-doped FCDs with an average size of 2 nm in a
subcritical water apparatus by using biomass waste (i.e., expired
milk) as the precursor. The obtained FCDs were highly dispersed in
aqueous solution because of the presence of O-containing functional
groups on their surfaces. Under the excitation of ultraviolet and
blue light, the FCDs exhibited excitation wavelength-dependent fluorescence
in the emission range of 400–550 nm. The FCDs could be easily
taken up by HeLa cells without additional surface functionalization,
serving as fluorescent nanoprobes for bioimaging. The applications
of FCDs as sensing agents for the detection of Fe3+, solid-state
fluorescent patterning, and transparent hybrid films were also performed,
demonstrating their potential for solid-state fluorescent sensing,
security labeling, and wearable optoelectronics.
In this study, a sensitive and efficient approach was developed for the determination of melamine (MEL) based on the combination of molecularly imprinted polymers (MIPs) with a synthesized fluorescent chemosensor.
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