Study on Chiral Symmetry Breaking during Growing Process of NaClO3 Crystal Under DC Electric Field
- Paper number
IAC-05-A2.1.03
- Author
Prof. Chen Wanchun, Chinese Academy of Sciences, China
- Coauthor
Prof. Xiaolong Chen, China
- Year
2005
- Abstract
Chirality is a geometrical concept that has captivated physicists and chemists since the time of Louis Pasteur. In nature, we find states of broken chiral symmetry at all levels, from elementary particles to the biosphere. The conception of chirality in physics and chemistry might be merely an academic one if it were not for the stunning fact that most of biochemistry is chiral. Proteins, DNA, amino acid, sugars and many natural products such as steroids, hormones and pheromones possess chirality. Indeed, classes of molecules such as amino acids are largely found to be homo-chiral. The exact origin of homochirality is one of the great-unanswered questions in evolutionary science. Mechanism and process that lead to transitions from a chiral symmetric state to a totally asymmetric state are thus of general interest. In general, if one is to use optically active crystals for synthetic, prebiotic, optical and other applications, one must be able to control the chirality of crystals during synthesis. It is well known that molecules crystallize in one of 230 possible space groups. Of these 230 groups, only 65 are chiral. Crystals residing in one of the 65 chiral space groups are innately chiral. The nucleation of achiral NaClO3 molecules to form optically chiral crystals is an example of symmetry breaking. It is interested that when sodium chlorate crystallized from an aqueous solution while the solution is not stirred, statistically equal numbers of levo- and dextro-NaClO3 crystals were found. When the solution was stirred, however the most of crystals (99.7 percent) have the same chirality, either levo- or dextro- behave. The previous researches have been shown that there are some chiral perturbations profoundly to alter the chiral distribution. These include the seeding, the addition of the optically active co-solutes, the chiral beta particles and positrons et al. Although these findings are important for understanding mechanism of the chiral symmetry breaking, there are many opening problems to be resolved. One of the questions is that if an applied force influences the chiral distribution? We become aware of the question and investigated chiral symmetry breaking during growth process of NaClO3 crystal under DC electric field. A sodium chlorate solution was prepared by dissolving the A.R. of the NaClO3 powder in distilled water. A saturated solution was prepared at 500C and measured by both Mach-Zehnder interferometry and a weight technique. A set of petri dishes with the diameter of 88-90 mm and the high of 13-15mm are adopted for growth cell, in which, the DC electric field with 3.4-17.0 V/cm was applied. The processes of spontaneous nucleation were completed with 2-4 hours. This paper will report the experimental results in detail.
- Abstract document
- Manuscript document
IAC-05-A2.1.03.pdf (🔒 authorized access only).
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