No abstract

A combination of pillar[5]-bis-trithiacrown (L) and mercury(II) halides afforded a monomer complex (Cl--form), a 1-D coordination polymer (Br--form) and a supramolecular ion-triplet complex [(I∙Hg∙I)@L] (I--form). In the ion-triplet complex, the...

Following the pioneering work of Sauvage and Stoddart on rotaxanes, construction of higher dimensional polyrotaxanes in metal–organic frameworks (MOFs) via a modified protocol is challenging. We present the formation of a two-dimensional (2D) polyrotaxane and its conversion to a three-dimensional (3D) polyrotaxane MOF via a photoreaction between interdigitated “olefin wheels”. For this purpose, a 2-fold entangled 2D MOF [Pb2(bpp)­(sdc)2] (1), showing a 2D + 2D → 2D polyrotaxane motif, has been synthesized from the solvothermal reaction of lead­(II) nitrate, 3,3′-stilbenedicarboxylic acid (H2sdc) containing an olefin group, and 1,4-bis­(4-pyridyl)­piperazine (bpp). The single-crystal X-ray diffraction analysis of 1 revealed that the adjacent entangled 2D layers are interdigitated, with the separation of 3.72 Å between CC bond pairs in adjacent layers satisfying Schmidt’s criteria for the occurrence of a [2 + 2] photocycloaddition reaction. Irradiation of the single crystals of 1 under UV light resulted in formation of a 3D polyrotaxane, [Pb2(bpp)­(rctt-tccb)] n (2), due to a [2 + 2] photocycloaddition reaction between two wheels via a single-crystal to single-crystal transformation. The photocycloaddition and partial thermal cleavage reaction between 1 and 2 were confirmed by 1H NMR and powder X-ray diffraction (PXRD) in solution and the solid state, respectively. The present approach could contribute to the understanding of the construction of higher dimensional polyrotaxanes which are not accessible by the traditional routes.

Adsorption behaviors of dodecanethiol (C12H25SH) molecules are investigated on the surface of single-walled carbon nanotubes (SWCNTs) with vibrational and X-ray photoelectron spectrometers. The active adsorption sites are proved as Stone-Wales (SW) defects (5–7 ring defects). The SW defect-removed SWCNTs formed by reacting nanotubes with allyl acrylate molecules are compared with pristine SWCNTs in dispersion and field emission. The former shows higher dispersion and field emission than the latter.

Here we report the development of a high throughput, all-solution phase, and isothermal detection system to detect African Swine Fever Virus (ASFV). CRISPR-Cas12a programmed with a CRISPR RNA (crRNA) is used to detect ASFV target DNA. Upon ASFV DNA binding, the Cas12a/crRNA/ASFV DNA complex becomes activated and degrades a fluorescent single stranded DNA (ssDNA) reporter present in the assay. We combine this powerful CRISPR-Cas assay with fluorescence-based point-of-care (POC) system we developed for rapid and accurate virus detection. Without nucleic acid amplification, a detection limit of 1 pM is achieved within 2 hrs. In addition, the ternary Cas12a/crRNA/ASFV DNA complex is highly stable at physiological temperature and continues to cleave the ssDNA reporter even after 24 hrs of incubation, resulting in an improvement of the detection limit to 100 fM. We show that this system is very specific and can differentiate nucleic acid targets with closely matched sequences. The high sensitivity and selectivity of our system enables the detection of ASFV in femtomolar range. Importantly, this system features a disposable cartridge and a sensitive custom designed fluorometer, enabling compact, multiplexing, and simple ASFV detection, intended for low resource settings.