Viedma ripening is the attrition-induced spontaneous chiral amplification of a conglomerate crystal mixture. To demonstrate the general nature of this deracemization process, we have extended attrition-enhanced chiral amplification to 10 achiral organic molecules that form conglomerate chiral crystals: benzil (1), diphenyl disulfide (2), benzophenone (3), tetraphenylethylene (4), guanidine carbonate (5), butylated hydroxytoluene (6), hippuric acid (7), ninhydrin (8), cytosine (9), and adeninium dinitrate (10). In these experiments the time required to reach homochirality was as low as 3 h and typically ranged from 25 to 50 h. In most cases amplification to homochirality of both enantiomers was observed in repeat experiments, although often in a nonstochastic fashion, reflecting the scalemic nature of the starting material. We have also demonstrated the utility of quantitative circular dichroism (CD) to determine enantiomeric excess in systems where chirality exists only in the solid-state.

No abstract

Both enantiomers of trans-cyclohexane-1,2-diammonium sulfate and trans-1,2-diphenylethylenediammonium sulfate were used as "tailor-made" additives to direct the mirror-symmetry breaking in the attrition-enhanced deracemization (i.e. Viedma ripening) of conglomerate crystals of ethylenediammonium sulfate (EDS). Isothermal titration calorimetry (ITC) shows chiral recognition of (1R,2R)- and (1S,2S)-1,2-diphenylethylenediamine to EDS crystals where the enthalpy of adsorption of the (1R,2R)-isomer on l-EDS crystals is higher in comparison to that on d-EDS crystals. These results are consistent with a "rule of reversal" mechanism driving the chiral outcome of the Viedma ripening of EDS.

No abstract

No abstract

No abstract

Oriented attachment, a nonclassical crystallization phenomenon, describes the spontaneous self-assembly of adjoining crystals with common crystallographic orientations. Introducing chiral recognition between crystals during oriented attachment enables enantiomer-specificity and the formation of homochiral structures. Herein, we report efficient enantiomer-specific oriented attachment for suspended crystals of guanidine carbonate to form mesoscale homochiral or enantioenriched aggregates under boiling or shaking conditions. These aggregates display polyhedral macrostructures and their chirality was monitored using circular dichroism and polarized light microscopy.

Background: The sedge mats (dyeing, weaving processes, and small-scale livestock farm at the same place) craft villages in the Mekong Delta (Vietnam) are the most popular craft villages in Vietnam, especially in the Mekong Delta area. These craft villages generate typical emissions such as exhaust gas from burning fuel, wastewater from the sedge mats dyeing and weaving process, wastewater from livestock farm, and solid waste. Methods: In this study, an ecological system, so-called VICRAIZES (Vietnam Craft villages Agro-based Industrial Zero Emission System), has been developed with the purpose to decrease pollution and enhance resource efficiency at those craft villages. The proposed ecosystem focused on measures such as (1) biogas tank (using residue pieces of solid sedge mats from weaving processing) supplied gas for burning the dyeing tank, (2) wastewater treatment system combining three components: innovative septic tank having upward flow thin baffles, anaerobic filter compartment, and bio-pond, and (3) composting area. The system was applied for a number of household craft villages in Dong Thap Province, Vietnam. Results: The results of system demonstration show significant emission decreases: 93 % greenhouse gas (CO 2 and CH 4 ), 97 % BOD 5 in wastewater, around 30 kg/day biodegradable garbage are composted and used as organic fertilizers at the household needs (which increase family income of around 115 million VND/year), low initial investment and operating cost, simple operating procedure, etc., which are favorable and applicable at the low income sedge mats dyeing and weaving craft villages in the Mekong Delta area, Vietnam, and probably at other developing countries. Conclusions: The VICRAIZES system implementation shows remarkable benefits/advantages on environmental, economic, and technical aspects giving real chances for more comprehensive application at similar craft villages in Vietnam and possibly in other developing countries.