Prediction for the separation efficiency of a pair of enantiomers during chiral high-performance liquid chromatography using a quartz crystal microbalance

Spin-Controlled Helical Quantum Sieve Chiral Spectrometer

This article reports on a molecular-spin-sensitive-antenna (MSSA) that is based on stacked layers of organically functionalized graphene on a fibrous helical cellulose network for carrying out spatiotemporal identification of chiral enantiomers. The MSSA structures combine three complementary features: (i) chiral separation via a helical quantum sieve for chiral trapping, (ii) chiral recognition by a synthetically implanted spin-sensitive center in a graphitic lattice; and (iii) chiral selectivity by a chirality-induced-spin mechanism that polarizes the local electronic band-structure in graphene through chiral-activated Rashba spin-orbit interaction field. Combining the MSSA structures with decision-making principles based on neuromorphic artificial intelligence shows fast, portable, and wearable spectrometry for the detection and classification of pure and a mixture of chiral molecules, such as butanol (S and R), limonene (S and R), and xylene isomers, with 95-98% accuracy. These results can have a broad impact where the MSSA approach is central as a precautionary risk assessment against potential hazards impacting human health and the environment due to chiral molecules; furthermore, it acts as a dynamic monitoring tool of all parts of the chiral molecule life cycles.

Enantioseparation/Recognition based on nano techniques/materials

Enantiomers show different behaviors in interaction with the chiral environment. Due to their identical chemical structure and their wide application in various industries, such as agriculture, medicine, pesticide, food, and so forth, their separation is of great importance. Today, the term "nano" is frequently encountered in all fields. Technology and measuring devices are moving towards miniaturization, and the usage of nanomaterials in all sectors is expanding substantially. Given that scientists have recently attempted to apply miniaturized techniques known as nano-liquid chromatography/capillary-liquid chromatography, which were originally accomplished in 1988, as well as the widespread usage of nanomaterials for chiral resolution (back in 1989), this comprehensive study was developed. Searching the terms "nano" and "enantiomer separation" on scientific websites such as Scopus, Google Scholar, and Web of Science yields articles that either use miniaturized instruments or apply nanomaterials as chiral selectors with a variety of chemical and electrochemical detection techniques, which are discussed in this article.

Separation of enantiomers by their enantiospecific interaction with achiral magnetic substrates

It is commonly assumed that recognition and discrimination of chirality, both in nature and in artificial systems, depend solely on spatial effects. However, recent studies have suggested that charge redistribution in chiral molecules manifests an enantiospecific preference in electron spin orientation. We therefore reasoned that the induced spin polarization may affect enantiorecognition through exchange interactions. Here we show experimentally that the interaction of chiral molecules with a perpendicularly magnetized substrate is enantiospecific. Thus, one enantiomer adsorbs preferentially when the magnetic dipole is pointing up, whereas the other adsorbs faster for the opposite alignment of the magnetization. The interaction is not controlled by the magnetic field per se, but rather by the electron spin orientations, and opens prospects for a distinct approach to enantiomeric separations.

Molecular recognition: from solution science to nano/materials technology

In the 25 years since its Nobel Prize in chemistry, supramolecular chemistry based on molecular recognition has been paid much attention in scientific and technological fields. Nanotechnology and the related areas seek breakthrough methods of nanofabrication based on rational organization through assembly of constituent molecules. Advanced biochemistry, medical applications, and environmental and energy technologies also depend on the importance of specific interactions between molecules. In those current fields, molecular recognition is now being re-evaluated. In this review, we re-examine current trends in molecular recognition from the viewpoint of the surrounding media, that is (i) the solution phase for development of basic science and molecular design advances; (ii) at nano/materials interfaces for emerging technologies and applications. The first section of this review includes molecular recognition frontiers, receptor design based on combinatorial approaches, organic capsule receptors, metallo-capsule receptors, helical receptors, dendrimer receptors, and the future design of receptor architectures. The following section summarizes topics related to molecular recognition at interfaces including fundamentals of molecular recognition, sensing and detection, structure formation, molecular machines, molecular recognition involving polymers and related materials, and molecular recognition processes in nanostructured materials.

Intelligent chiral sensing based on supramolecular and interfacial concepts

Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely discriminate chiral molecules, differentiation between chiral molecules in artificial systems is currently one of the challenging subjects in the field of molecular recognition. Therefore, one of the important challenges for intelligent man-made sensors is to prepare a sensing system that can discriminate chiral molecules. Because intermolecular interactions and detection at surfaces are respectively parts of supramolecular chemistry and interfacial science, chiral sensing based on supramolecular and interfacial concepts is a significant topic. In this review, we briefly summarize recent advances in these fields, including supramolecular hosts for color detection on chiral sensing, indicator-displacement assays, kinetic resolution in supramolecular reactions with analyses by mass spectrometry, use of chiral shape-defined polymers, such as dynamic helical polymers, molecular imprinting, thin films on surfaces of devices such as QCM, functional electrodes, FET, and SPR, the combined technique of magnetic resonance imaging and immunoassay, and chiral detection using scanning tunneling microscopy and cantilever technology. In addition, we will discuss novel concepts in recent research including the use of achiral reagents for chiral sensing with NMR, and mechanical control of chiral sensing. The importance of integration of chiral sensing systems with rapidly developing nanotechnology and nanomaterials is also emphasized.

Self-assembly and chiral recognition of quartz crystal microbalance chiral sensor

A novel chiral sensor based on the self-assembled monolayer of (6(A)-omega-mercaptoethylureado-6(A)-deoxy)heptakis(2,3-di-o-phenylcarbamoyl)-6(B), 6(C), 6(D), 6(E), 6(F), 6(G)-hexa-o-phenylcarbamoyl-beta-cyclodextrin (Ph-beta-CD-SH) on a quartz crystal transducer for chiral recognition was set up. (R,S)-(+/-)-(3-methoxyphenyl)ethylamine were recognized by this QCM chiral sensor with a QCM chiral discrimination factor of 1.33. Furthermore, UV spectroscopy was used to investigate the mechanism of host-guest interactions between (6(A)-azido-6(A)-deoxy)heptakis(2,3-di-o-phenylcarbamoyl)-6(B), 6(C), 6(D), 6(E), 6(F), 6(G)-hexa-o-phenylcarbamoyl-beta-cyclodextrin (Ph-beta-CD) and (R,S)-(+/-)-(3-methoxyphenyl) ethylamine. The UV discrimination factor was determined to be 0.066.

A novel strategy for rapid real-time chiral discrimination of enantiomers using serum albumin functionalized QCM biosensor

A novel and effective method has been developed for chiral discrimination using a quartz crystal microbalance (QCM) biosensor with self-assembled bovine serum albumin (BSA) or human serum albumin (HSA). The successfully constructed QCM chiral biosensors exhibited rapid and real-time enantioselective recognition. The QCM chiral discrimination factor (alpha(QCM)) can be calculated through resonance frequency shifts in response to five pairs of enantiomers. Moreover, the interactions between these ten enantiomers and two serum albumins (SA) were investigated in detail by means of ultraviolet-visible (UV-vis) and fluorescence (FL) spectra. The results indicated that the discrimination ability were quite different between BSA and HSA. R,S-1-(3-Methoxyphenyl)ethylamine (R,S-3-MPEA) and R,S-1-(4-methoxyphenyl)ethylamine (R,S-4-MPEA) can be easily differentiated by the BSA sensor, while the selectivity of the HSA sensor for R,S-tetrahydronaphthylamine (R,S-TNA), R,S-2-octanol (R,S-2-OT) and R,S-methyl lactate (R,S-MEL) was higher than that of the BSA sensor. The UV and FL spectra indicated the formation of a complex between SA and enantiomers and strong fluorescence quenching through static quenching mechanism. The in-depth study demonstrated that the calculated UV/FL discrimination factors (alpha(UV) and alpha(FL)) were consistent with the QCM experimental results (alpha(QCM)).