Luminescence spectrum near-infrared

Fiber optic sensors based on polymer swelling offer several potential advantages. They can be designed so that the optical measurement is separated from the polymer by a diaphragm so that the measurement can not be affected by the optical properties of the sample. Unlike fiber optic sensors based on indicator absorbance or luminescence, photodegradation is not a potential source of sensor instability. Measurements can be made in the near infrared region of the spectrum and take advantage of inexpensive components available for fiber optic communications. 

Energies in the infrared spectrum are conventionally expressed in wave numbers, which are defined as the number of waves per centimeter, i.e., the reciprocal of the wavelength measured in centimeters. The infrared spectrum extends from 12,500 to 50 cm (i.e., a wavelength of 0.8-200 fjLia.) and the far infrared from 40-10 cm (260 p.m-1 mm), but the upper limit of most commercial instruments is about 200 cm (50 ixm). Spectra are most frequently obtained by absorption and reflection techniques, but polarization, emission, and luminescence are also used (C26). Similar components are used in all types of instrument. Reflection measurements of samples with low transmission are made in the near infrared with a conventional spectrophotometer fitted with a reflec-... 

Figure 2c shows the near-infrared luminescence spectrum of [Gd(hfac)3NIT-BzImH] compared to its lowest-energy absorption band system. At 5 K, both spectra show well-resolved structure that is similar to the patterns observed for the uncoordinated radical, as summarized in Tables 1 and 2. The corresponding electronic transitions can be observed for many other complexes of lanthanide or d-block metal ions with radical ligands [24-27, 30]. In general, the spectra for lanthanide complexes are very similar to those of the uncoordinated radicals. 

Even larger probes of bent and kinked DNA are 40 A photoluminescent mineral colloidal particles of CdS [247-253]. These nanoparticles are approximately the size of proteins and can be made in a variety of sizes ( 20-100 A) and decorated with a variety of surface groups [267-279]. The emission spectrum of a nanoparticle solution depends on particle size and surface group synthetic procedures for CdS and other semiconductor nanoparticles have been developed so that the emission can be tuned throughout the visible spectrum and into the near infrared [267-279]. Moreover, the photoluminescence of CdS is sensitive to adsorbates [280-289], and thus these nanomaterials can function as luminescent chemical sensors. 

The lanthanides display luminescence in the spectral range from ultraviolet (UV) to near infrared (NIR). The spectral ranges are displayed in Fig. 3.3. The near infrared is a subsection of the infrared spectrum, ranging in wavelength from 0.75-1.4 pm. 

Figure 12 Electronic Raman spectrum (top trace and abscissa scale) and near-infrared luminescence spectrum (bottom trace and abscissa scale) of V(urea)6l3- The energy difference AE denoted by the horizontal double arrow indicates the ground state splitting.

Squaraines with ring substituents which absorb and emit in the red and near-infrared regions have also been developed [72]. When compared to conventional Cy5—NHS systems (open chain), these derivatives have several advantages. For example, these compounds can be excited not only with red lasers but also with blue lasers or with luminescent diodes being useful compounds, they can be excited all over the visible range of the electromagnetic spectrum. These compounds are particularly useful in biomedical applications due to their favorable spectral and photophysical properties, such as fluorescence [72]. 

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