Fluorescence Spectrometry
457
4 Modern Applications of FLS
Spectrophotometry is used as a basic toolbox in various fields like physical, chemical,
biological, and medical sciences. Some of the applications of spectrophotometry are
listed below:
• Determination of diamond structure by fluorescence:
The majority of diamonds do not show fluorescence, however, they exhibit a
weak fluorescence when they are exposed under a long-wave invisible UV light. In a
study done by the Gemological Institute of America, it is found that approximately
25–35% of diamonds exhibited some degree of fluorescence. Diamonds can exhibit
fluorescence at a variety of colors like green, red, yellow, orange, etc. depending upon
their atomic structure and presence of nitrogen like atoms; nevertheless, blue is the
most common color of diamond fluorescence (Fig. 10a). The presence or absence of
fluorescence in diamonds does not assay that it is real. The submicroscopic structures
in diamonds that cause fluorescence inherently weaken the durability of diamonds.
What impact does fluorescence have on the appearance of a diamond?
GIA studies showed that, for the overwhelming majority of diamonds, the strength
of fluorescence has no widely noticeable effect on appearance. In many instances,
observers prefer the appearance of diamonds that have medium to strong fluorescence. In rare cases, some diamonds with extremely strong fluorescence may appear
hazy or oily; fewer than 0.2% of the fluorescent diamonds submitted to GIA exhibit
this effect. The aforementioned information is retrieved from the research carried
out by the Gemological Institute of America.
• Off-On-Off” fluorescence probe for the sequential detection of Al
3+ and F
− :
Recently, an acylhydrazone fluorescence probe, SPBH, was synthesized from salicylaldehyde and 4-(pyridin-4-yl)benzohydrazide (PBH) that exhibits high selectivity and a sensitive fluorescence response towards Al
3+ . This chemosensor is
also able to detect Al
3+ in the intracellular region of human non-small cell lung
cancer H460 cells. This SPBH/Al
3+ complex also shows an excellent fluorescence
“turn-off” properties towards the F
− anion. Therefore, SPBH can acts as a sequential fluorescence “Off-On-Off” probe (Fig. 10b). However, the detection limits for
Al
3+ and F
− are found to be 1.1 × 10
−7 M and 1.47 × 10
−6 M, respectively
[19]. In another study, a method of detection and separation of toxic ions has been
developed via the introduction of competitive reactions into a long-alkyl-chained
acylhydrazone-based coumarin supramolecular polymer. This chemosensor shows
a sequential detection and separation of CN
− , Fe
3+ and S
2− , Ag
+ in water solution
with high selectivity and sensitivity [20].
• Protein dynamics and protein folding dynamics:
The structure of proteins and their dynamics including the folding dynamics have
gained experimental support by fluorescence spectroscopy [21]. Due to high sensi-
457
4 Modern Applications of FLS
Spectrophotometry is used as a basic toolbox in various fields like physical, chemical,
biological, and medical sciences. Some of the applications of spectrophotometry are
listed below:
• Determination of diamond structure by fluorescence:
The majority of diamonds do not show fluorescence, however, they exhibit a
weak fluorescence when they are exposed under a long-wave invisible UV light. In a
study done by the Gemological Institute of America, it is found that approximately
25–35% of diamonds exhibited some degree of fluorescence. Diamonds can exhibit
fluorescence at a variety of colors like green, red, yellow, orange, etc. depending upon
their atomic structure and presence of nitrogen like atoms; nevertheless, blue is the
most common color of diamond fluorescence (Fig. 10a). The presence or absence of
fluorescence in diamonds does not assay that it is real. The submicroscopic structures
in diamonds that cause fluorescence inherently weaken the durability of diamonds.
What impact does fluorescence have on the appearance of a diamond?
GIA studies showed that, for the overwhelming majority of diamonds, the strength
of fluorescence has no widely noticeable effect on appearance. In many instances,
observers prefer the appearance of diamonds that have medium to strong fluorescence. In rare cases, some diamonds with extremely strong fluorescence may appear
hazy or oily; fewer than 0.2% of the fluorescent diamonds submitted to GIA exhibit
this effect. The aforementioned information is retrieved from the research carried
out by the Gemological Institute of America.
• Off-On-Off” fluorescence probe for the sequential detection of Al
3+ and F
− :
Recently, an acylhydrazone fluorescence probe, SPBH, was synthesized from salicylaldehyde and 4-(pyridin-4-yl)benzohydrazide (PBH) that exhibits high selectivity and a sensitive fluorescence response towards Al
3+ . This chemosensor is
also able to detect Al
3+ in the intracellular region of human non-small cell lung
cancer H460 cells. This SPBH/Al
3+ complex also shows an excellent fluorescence
“turn-off” properties towards the F
− anion. Therefore, SPBH can acts as a sequential fluorescence “Off-On-Off” probe (Fig. 10b). However, the detection limits for
Al
3+ and F
− are found to be 1.1 × 10
−7 M and 1.47 × 10
−6 M, respectively
[19]. In another study, a method of detection and separation of toxic ions has been
developed via the introduction of competitive reactions into a long-alkyl-chained
acylhydrazone-based coumarin supramolecular polymer. This chemosensor shows
a sequential detection and separation of CN
− , Fe
3+ and S
2− , Ag
+ in water solution
with high selectivity and sensitivity [20].
• Protein dynamics and protein folding dynamics:
The structure of proteins and their dynamics including the folding dynamics have
gained experimental support by fluorescence spectroscopy [21]. Due to high sensi-