Light from chemical reactions

Apart from the classification based on sensing mechanisms, biosensors are classified into three categories considering the transduction mechanism used. They are optical, electrochenfical, or electrical. The optical transduction mechanism includes fluorescence, chemilununescence, interferometry, and surface plasmon resonance. These techniques involve either the production of light from chemical reactions or the change in refractive index at the interface of biosensing materials. 

In addition to protection from breakage, the brown plastic bottles in which hydrogen peroxide is commonly sold enhance the shelf-life of this product. Packaging plays an important role in limiting the light-induced chemical reactions of hydrogen peroxide. 

In most instances, no light was visible. In a few of the more violent tests, there were flashes of light and these were assumed to result from chemical reactions. 

The energy of excitation may arise from chemical reaction, by absorption of light, or by thermal excitation. Chemical reaction in flames gives rise to electronically excited species, and it is the emission from these excited states that give rise to the characteristic flame b2mds . ... 

Luminescence is light emission from materials caused by other processes, such as light absorption, chemical reaction, impact with electrons, radioactivity, or mechanical shock. 

The reaction of potassium perchlorate and sulfur in these highway flares produces a spontaneous release of energy as heat and light. The bright red color comes from the emission of light by strontium in the form of strontium nitrate mixed with the other substances. Chemists have learned how to control and manage the energy from chemical reactions and make it do useful work. 

Normally they can be controlled from outside as, via a random light illumination (chemical reactions) [26] or the pump light (lasers) [49]. 

Thomson (15) states that most of the electricity which passes through an ordinary tungsten lamp is converted to heat (98% for a 100 watt lamp) not light . Because chemical reactions are accelerated in the presence of increased heat, the conditions are prime for chemical and physical deterioration of the artifact. If a fluorescent bulb were substituted for an incandescent bulb, the heat emission would be diminished, provided that the element were separated from the display case. However, extremely energetic UV radiation would be introduced (15). 

Bioluminescence- and Chemiluminescence-Based Biosensors These reactions are the most sensitive chemical probes. The simplest accepted mechanism for the production of light from biological reactions is that of the cmstacean Cypridina hilgendorfii ... 

The effects of heat and light on chemical reactions have long been known and understood. Ultrasound has been known to promote chemical reactions for the past 60 years, but despite this, it did not attract the attention of synthetic chemists until recently. This arose historically from early studies which concentrated almost exclusively on reactions in aqueous media and was also, in some measure, due to the availability of suitable technology. Since the early 1980s a plethora of literature has appeared of direct interest to synthetic chemists and the field has been developing rapidly. 

The combination of ion traps with lasers has opened up a wide range of innovative experiments. In addition to the information obtained from detecting reemitted or stimulated photons, there are many laser based schemes for probing or manipulating a trapped ensemble including optical pumping, laser induced dissociation, or light stimulated chemical reactions. Lasers are utilized for state specific creation of ions in the trap. 

Luminescence, which is the emission of light, can result from chemical reactions or exdtation by light. The former can be artifidal (for instance the reaction of luminol plus hydrogen peroxide) or the response of the stimulation of natural reactions of photoproteins (see the discussion of the kinetics of aequorin in section 4.2). The form of luminescence of most general interest for kinetic studies is that obtained in response to exdtation by light (fluorescence and phosphorescence). All forms of luminescence are due to the emission of photons from electronically excited states. In the singlet exdted state the electron in the higher orbital has opposite spin... 

For both aqueous and nonaqueous liquids, the emission spectra fl om MBSL suggests that the principal source of light emission is from chemical reactions involving high-energy species formed during cavitation by bubble collapse. MBSL is principally a form of chemiluminescence, just as flame emission is. 

Second-order effects include experiments designed to clock chemical reactions, pioneered by Zewail and coworkers [25]. The experiments are shown schematically in figure Al.6.10. An initial 100-150 fs pulse moves population from the bound ground state to the dissociative first excited state in ICN. A second pulse, time delayed from the first then moves population from the first excited state to the second excited state, which is also dissociative. By noting the frequency of light absorbed from tlie second pulse, Zewail can estimate the distance between the two excited-state surfaces and thus infer the motion of the initially prepared wavepacket on the first excited state (figure Al.6.10 ). 

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