Although surface-enhanced Raman spectroscopy (SERS) can
rapidly
identify molecular fingerprints and has great potential for analysis,
the need for delicate plasmonic substrates and complex laboratory
instruments seriously limits its applicability for on-site detection.
This paper describes the development of an inexpensive aluminum nanoparticle
(AlNP)-decorated paper that functions as a facile SERS-based detection
platform (Al-PSERS). Polydopamine-protected AlNPs were chemically
synthesized and then simply drop-cast onto a hydrophobic cellulose
paper, forming a monolayer AlNP cluster array. Because of the abundance
of hot spots arising from the plasmonic clusters, the inherent quasi-three-dimensional
structure of the cellulose fibers, and the concentration effect of
the hydrophobic surface, the Al-PSERS provided significant enhancements
to the signal of various analytes, measured using a portable 785 nm
Raman spectrometer. Near-field optical simulations and experimental
spectroscopic results revealed that the local electric fields and
corresponding SERS signal intensities of the AlNP array exhibited
clear particle-length and cluster-size dependencies. Therefore, the
Al-PSERS could be optimized to provide high sensitivity (enhancement
factor: 2 × 103) and excellent reproducibility (variation:
8.72%). Moreover, the optimal Al-PSERS was capable of detecting colorants
and environmental pollutants; for example, the detection limits of
allura red and benzo[a]pyrene reached as low as 3.5
and 0.15 ppm, respectively. Furthermore, the Al-PSERS could rapidly
identify illegal (rhodamine B) and edible (allura red, erythrosine)
colorants from a mixture of multiple colorants or from adulterated
candies. Because it facilitates rapid detection, is of low cost, and
has minimal technical requirements, Al-PSERS should be applicable
to on-site detection in, for example, food inspection and environmental
monitoring.
Thin copper film has been successfully electrodeposited onto the Bi‐Pb‐Sr‐Ca‐Cu‐O superconductor substrate from aqueous solution. The electrical and magnetic properties of copper‐superconductor composite structure were evaluated by two‐ and four‐point resistivity measurements and magnetic susceptibility data. The electrodeposition process was shown to have little effect on the intrinsic properties of the superconductor substrate from resistivity measurements. Almost no degradation of the bulk properties was observed from the magnetization data. Scanning electron microscope and electron probe microanalysis were used to analyze the morphology of the substrate surface and the composition of the copper‐superconductor interface. The copper‐superconductor contact was found to have a linear characteristic by I‐V data at 300 and 77 K.
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