Temporal and spatial changes in neurotransmitter concentrations are central to information processing in neural networks. Therefore, biosensors for neurotransmitters are essential tools for neuroscience. In this work, we applied a new technique, corona phase molecular recognition (CoPhMoRe), to identify adsorbed polymer phases on fluorescent single-walled carbon nanotubes (SWCNTs) that allow for the selective detection of specific neurotransmitters, including dopamine. We functionalized and suspended SWCNTs with a library of different polymers (n = 30) containing phospholipids, nucleic acids, and amphiphilic polymers to study how neurotransmitters modulate the resulting band gap, near-infrared (nIR) fluorescence of the SWCNT. We identified several corona phases that enable the selective detection of neurotransmitters. Catecholamines such as dopamine increased the fluorescence of specific single-stranded DNA-and RNAwrapped SWCNTs by 58−80% upon addition of 100 μM dopamine depending on the SWCNT chirality (n,m). In solution, the limit of detection was 11 nM [K d = 433 nM for (GT) 15 DNA-wrapped SWCNTs]. Mechanistic studies revealed that this turn-on response is due to an increase in fluorescence quantum yield and not covalent modification of the SWCNT or scavenging of reactive oxygen species. When immobilized on a surface, the fluorescence intensity of a single DNA-or RNA-wrapped SWCNT is enhanced by a factor of up to 5.39 ± 1.44, whereby fluorescence signals are reversible. Our findings indicate that certain DNA/ RNA coronae act as conformational switches on SWCNTs, which reversibly modulate the SWCNT fluorescence. These findings suggest that our polymer−SWCNT constructs can act as fluorescent neurotransmitter sensors in the tissue-compatible nIR optical window, which may find applications in neuroscience.

No abstract

UiO-66 is an archetypal metal−organic framework (MOF) with a very high surface area as well as high thermal stability. It is found that the stability can be attributed to the metal oxide node being cuboctahedral allowing for 12 extension points for 1,4-benzenedicarboxylic acid (BDC) coordination. Because of this and its exceptional tunability and functionality, which are largely due to defect control of both missing-cluster and missinglinker defects, UiO-66 has gained scientific popularity. The combination of these characteristics allows for a highly versatile material that can be adapted to many different applications. The purpose for this work is to provide a historic overview of UiO-66, outlining the major developments that changed the synthesis strategies of Zr-based MOF as well as current and future works, which include defect control, aqueous crystallization, functionality-stability trade-offs, and advanced topographies. A breakdown of the various UiO-66 structures, including isoreticular and reo-type, and different characterization techniques such as powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and nitrogen porosimetry are discussed as well.

Molecular recognition is central to the design of therapeutics, chemical catalysis and sensors. Motifs for doing so most commonly involve biological structures such as antibodies and aptamers. The key to such biological recognition consists of a folded and constrained heteropolymer that, via intra-molecular forces, forms a unique three dimensional structure that creates a binding pocket or an interface able to recognize a specific molecule. In this work, we demonstrate that synthetic heteropolymers can be alternatively constrained by adsorption around a nanoparticle, and specifically a single walled carbon nanotube (SWNT), forming a corona phase and resulting in a new form of molecular recognition of specific molecules. The phenomenon is shown to be generic, with new heteropolymer recognition complexes demonstrated for three distinct examples: Riboflavin, l-thyroxine, and estradiol, each predicted using a 2D thermodynamic model of surface interactions. The dissociation constants are continuously tunable by perturbing the chemical structure of the heteropolymer. Moreover, these complexes can be used as new types of spatial-temporal sensors based on modulation of SWNT photoemission in the near-infrared, as we show by tracking riboflavin diffusion in murine macrophages.

The vision for graphene and other two-dimensional electronics is the direct production of nanoelectronic circuits and barrier materials from a single precursor sheet. DNA origami and single-stranded tiles are powerful methods to encode complex shapes within a DNA sequence, but their translation to patterning other nanomaterials has been limited. Here we develop a metallized DNA nanolithography that allows transfer of spatial information to pattern two-dimensional nanomaterials capable of plasma etching. Width, orientation and curvature can be programmed by specific sequence design and transferred, as we demonstrate for graphene. Spatial resolution is limited by distortion of the DNA template upon Au metallization and subsequent etching. The metallized DNA mask allows for plasmonic enhanced Raman spectroscopy of the underlying graphene, providing information on defects, doping and lattice symmetry. This DNA nanolithography enables wafer-scale patterning of two-dimensional electronic materials to create diverse circuit elements, including nanorings, three-and four-membered nanojunctions, and extended nanoribbons.