Sample nanomaterial applications

Nanostructured electrode arrays and nanomaterial-based labeling strategies have resulted in ultrasensitive devices for measuring clinically relevant biomolecules. Due to their small size, electrocatalytic properties, compatibility with microfluidics, and ability to be functionalized with biomolecules, nanomaterial-derived electrochemical biosensor arrays have shown promise in applications that require the simultaneous detection of multiple biomolecules. As personalized medicine and future medical diagnostics require the development of small, sensitive, versatile, low-cost, and energy-efficient devices for multiplexed detection of biomolecules from complex samples, nanomaterial-based bioelectrochemistry is poised to address the rigorous demands of biosensor development. 

The types of organic species extracted using SPE and the variety of samples analyzed has increased impressively and is mainly a result of the application of new smart materials as sorbent materials (e.g., immunosorbents, molecular printed polymers, carbon nanomaterials). 

While these techniques are widely used, they do not provide sufficient purity. Liquid phase purification is not an environmentally friendly process and requires corrosion-resistant equipment, as well as costly waste disposal processes. Alternative dry chemistry approaches, such as catalyst-assisted oxidation or ozone-eiuiched air oxidation, also require the use of aggressive substances or supplementary catalysts, which result in an additional contamination. Moreover, in many previous studies trial and error rather than insight and theory approaches have been applied. As a result, a lack of understanding and limited process control often lead to extensive sample losses of up to 90%. Because oxidation in air would be a controllable and enviromnentaUy friendly process, selective purification of carbon nanomaterials, such as CNT and ND, in air is very attractive. In contrast to current purification techniques, air oxidation does not require the use of toxic or aggressive chemicals, catalysts, or inhibitors and opens avenues for numerous new applications of carbon nanomaterials. 

The effects of catalysts on the oxidation temperature can be significant. For example, lead (Pb), copper (Cu), silver (Ag), iron (Fe), platinum (Pt), and nickel (Ni) were found to lower the ignition temperature of graphite powder from 740°C to 382°C, 570°C, 585°C, 593°C, 602°C, and 613°C, respectively [21]. In all of these cases, the concentration of the metal in the sample was <0.2 wt.%. While catalysts are widely used for large-scale production of chemicals and play an important role in biological processes, they are considered as impurities in the case of carbon nanomaterials as they alter their properties and limit the number of potential applications. 

As previously discussed, transmission mode is applicable only to thin/ nanomaterials or transparent samples even though the detection efficiency is very high owing to the capability of high NA objective lens. In order to apply tip enhancement to opaque or bulk samples such as silicon-based materials, reflection mode TERS has been developed [26, 86-90]. The idea of the reflection mode is very simple in a way that both illumination and detection are conducted at the same side of the tip and the samples surface as illustrated in Fig. 16.4b. The illumination can be either normal or oblique to the sample surface. Illumination depends on the availability of the space between objective lens and the SPM head. This critical issue is often solved using a relatively low NA objective lens with a long working... 

Due to the successful applications of the JMAK formal theory to a wide range of nucleation and growth phenomena in macroscopic samples, researchers have tried to employ the JMAK theory to model phase transitions in nanomaterials systems. This has been successful in some cases (Lu and Wang 1991 Luck el al. 1993 Varga et al. 1994 Luck et al. 1996 Damson et al 1996 Missana et al. 1999 Schmidt et al. 2000). However, other studies suggest that applications of the general JMAK theory to nanomaterials systems are only partially satisfactory (Allia et al. 1993 Illekova et al. 1996 Malek et al. 1999 ), or even inappropriate (Nicolaus et al. 1992 Gloriant et al. 2000). 

Synchrotron-based nuclear resonance methods have revealed the vibrational dynamics of the iron atom in numerous systems, including alloys, amorphous materials, nanomaterials, and materials under high pressure. The above-mentioned selectivity for the probe nucleus is particularly valuable for biological macromolecules, which may contain many thousands of atoms, but a localized active site is often the true center of interest. Since its availability, NRVS has been applied to study the vibrational dynamics of Fe in proteins, porphyrin model compounds, " and iron-sulfur clusters. It is shown that NRVS can provide frequencies, amplitudes, and directions for Fe vibrations in the samples. It helps to clarify mode assignments in vibrational spectra and reveals many important vibrational modes of Fe that cannot be seen by other methods. In particular, NRVS reveals low-frequency motions of the Fe down to below 100 cm that control biological reactions. The applications presented here use Fe as the probe nucleus, but the principle applies to other Mossbauer isotopes such as " Sn, Kr, Ni, and Zn if appropriate sources are available. 

In this review we described the most commonly used label-free aptasensor strategies. Although aptamers are one of the most promising systems for applications in biosensors, their potential applications using complex matrices as real samples remain the major challenges for point-of-care applications therefore, complementary strategies involving nanomaterials are a subject of intense study. 

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