Environmental Engineering Reference
In-Depth Information
collective oscillation of the conduction electrons and is known as the localized surface
plasmon resonance (LSPR). The LSPR induces electromagnetic fields surrounding the
NPs and, thus, enhances the sensing signal by 8 - 14 orders of magnitude observed in
surface-enhanced Raman scattering (SERS). With LSPR, SERS has transformed Raman
spectroscopy from the least sensitive vibration spectroscopy to the only single-molecule
spectroscopy, workable under ambient conditions, in aqueous media, and with the
sensitivity sufficient for trace-level detection. Because LSPR- and SERS-based
techniques only need simple, small, light, robust, and low-cost equipment, LSPR
nanosensors have great potentials for combat, field-portable environmental or point-of-
service medical diagnostic applications (Willets and van Duyne, 2007). To date, a
variety of chemically and biologically relevant molecules can be detected by LSPR
sensors-from biomarkers of Alzheimer's disease and anthrax to the direct detection of
glucose and chemical-warfare agents (Willets and van Duyne, 2007). Considerable
research on LSPR sensors or nanosensor arrays has been focused on (a) using the
sensors (not arrays) to monitor the binding of molecules onto the surface-bound species
of the sensors (e.g., antibody-antigen, DNA-DNA, and DNA-protein interactions), (b)
sensitivity of NP shapes and structures to bulk refractive index changes. Recently, nano-
or micro-line arrays fabricated with microfluidic channels formed in
poly(dimethylsiloxane) (PDMS) and then attached to either glass or gold surfaces have
been used in LSPR tests for detection of DNAs and RNAs (Lee et al, 2001), which
opened the widow for developing multiplexed nanoarrays for multi-analyte detection.
It should be pointed out that nanotechnologies can be combined with existing
micro-technologies and/or micro-systems to have a significant impact on nearly all
environmental branches (Fecht and Werner, 2004). For example, micromachined
cantilevers-based sensors have a significant advantage in the absolute sensitivity
achievable; novel coating methods are making these sensors more robust and
reproducible. Since the invention of atomic force microscopy (AFM), AFM-based
probes are used as the key component in teleoperated and automatic nanomanipulation
systems, an emerging area enabling precise measurement and control of nanoscale
phenomena. Nowadays, the potential to modify AFM cantilevers into different AFM
probes has been demonstrated by attaching materials such as a FIRAT tip (for fast
topographic imaging), and nanoscale electrodes (for biological activity). The interactions
between a NM and a single microorganism can be evaluated directly if an AFM
cantilever is coated or attached to the NM (Poggi et al., 2004a, 2004b; Torun et al.,
2007). Furthermore, Georgia Tech researchers have created a nanoscale probe, the
Scanning Mass Spectrometry (SMS) probe that can gently pull biomolecules (proteins,
metabolites, and peptides) precisely at a specific point on the cell/tissue surface, ionize
these biomolecules and produce “dry” ions suitable for analysis and then transport those
ions to the mass spectrometer for identification. The probe does this dynamically (not
statically), creating images similar to movies of cell biochemical activities with high
spatial and temporal resolution. The SMS probe can be readily integrated with the
 
Search WWH ::




Custom Search