Ti–Si–Zr–Zn Nanometallic Glass Substrate with a Tunable Zinc Composition for Surface-Enhanced Raman Scattering of Cytochrome c

Abstract

As a remarkably powerful analytical technique, surface-enhanced Raman scattering (SERS) continues to find applications from molecular biology and chemistry to environmental and food sciences. In search of reliable and affordable SERS substrates, the development has moved from noble metals to other diverse types of structures, e.g., nano-engineered semiconductor materials, but the cost of the enhancement factors (EF) substantially decreasing. In this work, we employ biocompatible thin films of Ti–Si–Zr–Zn nanometallic glasses as the SERS substrates, while tuning the Zn composition. Aided by quartz crystal microbalance, we find that the composition of 4.3% Zn (Ti–Si–Zr–Zn4.3) gives an ultrasensitive detection of Cytochrome c (Cyt c) with an EF of 1.38 × 104, 10-fold higher than the previously reported EF in the semiconducting metal oxide nanomaterials, such as TiO2, and even comparable to the reported noble-metal-assisted semiconducting tungsten oxide hydrate. Ti–Si–Zr–Zn4.3 exhibits a stronger adhesion force toward Cyt c, which ensures the strong binding of Cyt c to the surface, facilitating the Cyt c adsorption onto the surface and thus enhancing the SERS signal. The high separation efficiency of photoinduced electrons and holes in Ti–Si–Zr–Zn4.3 is also acknowledged for promoting the SERS activity.

Cation Chain Length of Nonhalogenated Ionic Liquids Matters in Enhancing SERS of Cytochrome c on Zr–Al–Co–O Nanotube Arrays

“…The conducted XRD analysis indicated that no sharp diffraction peaks corresponding to the crystalline phases were detected in the as-anodized ZACO (Figure b). The appearance of a visible broad hump in the XRD pattern of ZACO confirms the amorphous character, which has been proven to be positive for enhancing SERS signals . The EDS analysis of ZACO in Figure (c) confirmed the presence of Zr, Al, Co, and O elements, with the corresponding atomic percentages of 28, 7, 12, and 53%.…”

“…Thus, in the water-rich Cyt c solution with a lower amount of P 6 M (0.005 g), the cations and anions are highly dissociated, and the dissociation extent is larger in comparison with that possessing a higher concentration of P 6 M (0.01 g). It should be noted that the concentration of the IL is lower in Cyt c –P 6 M (0.005)–ZACO than in Cyt c –P 6 M–ZACO (0.01 g IL), resulting in less free ions in the system with 0.005 g of P 6 M that contribute to ionic conductivity, not beneficial to the charge-transfer process, and thus the SERS performance . However, a further increase of P 6 M to 0.05 g led to an increased association of cation–anion pairs and thus less free ions contributing to ionic conductivity, ultimately resulting in weaker SERS signals of Cyt c .…”

“…For example, a thin film of amorphous Ti–Si–Zr–Zn nanometallic glass with a zinc concentration of 4.3% was created to demonstrate a strong interaction with the probe molecule (cytochrome c , Cyt c ), associated with more adsorbed Cyt c , giving a remarkable SERS enhancement. In contrast, Ti–Si–Zr–Zn nanometallic glasses with either a higher or lower concentration of zinc exhibit a weaker interaction with Cyt c , resulting in the weak adsorption of Cyt c and the nonsignificant enhancement of SERS signals . The interactions of TiO 2 nanotube arrays with Cyt c were found to increase as the tubular size increased, associated with more adsorptive amounts of Cyt c and thus higher SERS enhancement factors (EFs) .…”

“…Amorphous Zr–Al–Co–O nanotube arrays were selected as the SERS substrate in the present work because of the following reasons. (1) Amorphous nanomaterials can facilitate an easier escape and transfer of the surface electrons due to their long-range disordered structure. − Our previous work demonstrated that amorphous Ti–Si–Zr–Zn nanometallic glasses show a strong interaction with Cyt c , exhibiting a remarkable SERS enhancement . (2) The Ni-decorated ZrAlCo–O nanotube arrays were found to show a short response time and ultrahigh sensitivity in the detection of glucose .…”

Ordered Anodic Aluminum Oxide-Based Nanostructures for Surface-Enhanced Raman Scattering: A Review

“…Considering the high expense associated with noble metals, researchers have explored alternative materials for constructing SERS substrates. Particularly, semiconductor materials have been demonstrated to have high stability, cost effectiveness, and enhanced biocompatibility . Nowadays, many kinds of semiconductor materials, such as graphene and its derivatives, transition metal oxides, and metal–organic composites, have been studied as material choices of SERS substrates and exhibited considerable SERS activity. − However, achieving reproducible and repeatable SERS enhancement along with accurately interpreting SERS signals remain significant challenges due to variable particle size, morphology, random distribution, and uncontrollable nanoparticle aggregation .…”