Abstract
Silver nanoparticles were synthesized by an enzyme-induced growth process on solid substrates. In order to customize the enzymatically grown nanoparticles (EGNP) for analytical applications in biomolecular research, a detailed study was carried out concerning the time evolution of the formation of the silver nanoparticles, their morphology, and their chemical composition. Therefore, silver-nanoparticle films of different densities were investigated by using scanning as well as transmission electron microscopy to examine their structure. Cross sections of silver nanoparticles, prepared for analysis by transmission electron microscopy were additionally studied by energy-dispersive X-ray spectroscopy in order to probe their chemical composition. The surface coverage of substrates with silver nanoparticles and the maximum particle height were determined by Rutherford backscattering spectroscopy. Variations in the silver-nanoparticle films depending on the conditions during synthesis were observed. After an initial growth state the silver nanoparticles exhibit the so-called desert-rose or nanoflower-like structure. This complex nanoparticle structure is in clear contrast to the auto-catalytically grown spherical particles, which maintain their overall geometrical appearance while increasing their diameter. It is shown, that the desert-rose-like silver nanoparticles consist of single-crystalline plates of pure silver. The surface-enhanced Raman spectroscopic (SERS) activity of the EGNP structures is promising due to the exceptionally rough surface structure of the silver nanoparticles. SERS measurements of the vitamin riboflavin incubated on the silver nanoparticles are shown as an exemplary application for quantitative analysis.
Highlights
The application of metal nanoparticles in the field of bioanalytics extends the possibilities of biomolecular detection significantly and may satisfy the ever-growing interest in ultrasensitive detection methods for different applications [1]
In the following we report on investigations of the morphology and the composition of silver nanoparticles generated by means of an enzymatically induced redox reaction
The properties of the silver nanoparticles were characterized in dependence on the DNA concentration for binding of the enzyme and the reaction time in order to obtain samples with different densities and sizes of silver enzymatically grown nanoparticles (EGNP)
Summary
The application of metal nanoparticles in the field of bioanalytics extends the possibilities of biomolecular detection significantly and may satisfy the ever-growing interest in ultrasensitive detection methods for different applications [1]. Investigations based on optical, electrical, electrochemical, or gravimetric detection schemes [2,3,4] Concerning their optical properties, metal nanoparticles are characterized by high extinction coefficients as well as large scattering cross sections, making them prospective candidates for optical approaches based on absorption or scattering processes [5]. Another simple and robust approach for the detection of biomolecules utilizing properties of metal nanoparticles is the measurement of the electrical conductivity. Even though the application of nanoparticles for the detection of biomolecules is already widespread, its full potential has not been exploited yet, since the performance of the metal nanoparticles as well as of core–shell particles strongly depends on their size, morphology, and composition, which have to be optimized for bioanalytical investigations
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