Quantum Physics of Photosynthesis by Uğur Güney
The reason has to do with quantum physics at the surfaces. If the semiconductor is in contact with a metal, said Lewis, "you find that the resultant voltages are less than thermodynamics analysis predicts," because of interfacial reactions. A similar problem plagues the interface between two semiconductors of different electrical characters. "If you try to match their surfaces with atomic precision, you will pay a price" to do so, said Lewis, and thus drive up the economic cost of the system. "When you miss at certain spots, those spots become recombination sites," and some of the free charge meant to be collected as electricity is drained into these surface reactions. Using a liquid at the interface obviates both of these problems. First, one can add into the liquid something else that will have a high affinity for the defective sites that could have led to problematic recombination, and can thereby passivate these sites. Second, one can reduce the danger of back electron transfer by choosing a solvent that draws electrons more strongly and increases their forward rate.
Wolfgang Thies: Quantum Mechanics In Photosynthesis of Plants
Quantum physics provides a suggestive, if incomplete, explanation of why the electron does not transfer ever more quickly as more energy is applied. McLendon explained that when an electron is lost from one molecule (a donor) and gained by another (an acceptor), the lengths of the bonds in each molecule change, like a stretching spring. The energy for this stretching, called the "reorganization energy," said McLendon, "is supplied by the excess [free] energy of reaction. The fastest rate occurs when the reaction free energy exactly equals the reorganization energy. If less energy is available, the bonds can't be stretched enough for reaction to occur." Conversely, continued McLendon, ''if too much energy is available, the system must wait for this extra energy to 'dribble' away, since at the instant of transfer, the energy of the starting materials and products must be equal, by the law of conservation of energy."
McLendon is a chemist specializing in the quantum processes of moving electrons from one molecule to another. Not focusing exclusively on photosynthesis, he usually works with proteins and biological systems, but his laboratory has demonstrated phenomena crucial to all electron transfer systems. The basic physics involves the concept of conservation of energy, which, explained McLendon, shows that an electron's rate of transfer varies with the energy force driving it. Essential to the first step in photosynthesis, this relationship between rate and energy was analyzed theoretically some years ago by Rudy Marcus (1956) at Caltech, who predicted an anomaly that was first confirmed by John Miller at Argonne National Laboratory, and verified subsequently by McLendon and others. Up to a certain level of energy, the rate of electron transfer increases with the force driving it, but the initially proportional relationship changes. After the peak level is reached, additional driving force actually slows the electron down. "A funny thing," said McLendon, "is that you can have too much of a good thing."
The idea that plants make use of quantum physics to ..
The majority of light-gathering macromoleculesare composed of chromophores (responsible for the colour of molecules) attachedto proteins, which carry out the first step of photosynthesis, capturingsunlight and transferring the associated energy highly efficiently. Previousexperiments suggest that energy is transferred in a wave-like manner,exploiting quantum phenomena, but crucially, a non-classical explanation couldnot be conclusively proved as the phenomena identified could equally bedescribed using classical physics.
Quantum physics and photosynthesis make solar cells brilliant
Light-gathering macromolecules in plant cells transfer energy by taking advantage of molecular vibrations whose physical descriptions have no equivalents in classical physics, according to the first unambiguous theoretical evidence of quantum effects in photosynthesis published today in the journal Nature Communications.
An almost complete quantum mechanical picture of photosynthesis is ..
Often, to observe or exploit quantummechanical phenomena systems need to be cooled to very low temperatures. Thishowever does not seem to be the case in some biological systems, which displayquantum properties even at ambient temperatures.