RESUMEN

This work describes a rapid and highly sensitive method for the quantitative detection of an important biomarker, uric acid (UA), via surface-enhanced Raman spectroscopy (SERS) with a low detection limit of ~0.2 µM for multiple characteristic peaks in the fingerprint region, using a modular spectrometer. This biosensing scheme is mediated by the host-guest complexation between a macrocycle, cucurbit[7]uril (CB7), and UA, and the subsequent formation of precise plasmonic nanojunctions within the self-assembled Au NP: CB7 nanoaggregates. A facile Au NP synthesis of desirable sizes for SERS substrates has also been performed based on the classical citrate-reduction approach with an option to be facilitated using a lab-built automated synthesizer. This protocol can be readily extended to multiplexed detection of biomarkers in body fluids for clinical applications.

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RESUMEN

We demonstrate that the reproducibility of sensors for nitroaromatics based on surface-enhanced Raman spectroscopy (SERS) can be significantly improved via a hierarchical aqueous self-assembly approach mediated by the multifunctional macrocyclic molecule cucurbit[7]uril (CB[7]). Our approach is enabled by the novel host-guest complexation between CB[7] and an explosive marker 2,4-dinitrotoluene (DNT). Binding studies are performed using experimental and computation techniques to quantify key binding parameters for the first time. This supramolecular complexation allows DNT to be positioned in close proximity to the plasmonic hotspots within aggregates of CB[7] and gold nanoparticles, resulting in significant SERS signals with a detection limit of ∼1 µM. The supramolecular ensemble is selective against a structurally similar nitroaromatics owing to the molecular-recognition nature of the complexation as well as tolerant against the presence of model organic contaminants that bind strongly to the SERS substrates.

RESUMEN

Self-assembled nanoparticles have important applications in energy systems, optical devices and sensors, via the formation of aggregates with controlled interparticle spacing. Here we report aqueous self-assembly of rigid macrocycle cucurbit[7]uril (CB[7]) and fluorescent quantum dots (QDs), and demonstrate the potential of the system for efficient energy transfer and sensing of small molecules.

RESUMEN

Tetrabutylammonium (TBA) and tetraphenylborate (TPB) ions dissolved in dichloroethane (DCE) are widely used in electrochemistry of liquid-liquid interfaces. Unlike alkali halide solutions in water, TBA-TPB-DCE solutions feature large organic ions and a solvent with a dielectric constant almost one order of magnitude lower than that of water. This is expected to dramatically amplify the impact of ionic correlations in the properties of the solution. Here we report atomistic simulations of TBA-TPB-DCE solutions and analyze ion correlations, clustering, and charge screening effects. We target concentrations in the range of 0.01-0.25 molal (m), hence exploring concentration regimes typical for many experimental investigations. We show that the transition from monotonic to oscillatory decay of the charge density, which signals the onset of strong ion correlations, takes place in this concentration interval, leading to overscreening effects. Furthermore, we investigate the distribution and adsorption of ions at the DCE-air interface. Unlike what is observed for small inorganic ions in water at similar concentrations, we find that TPB and TBA ions accumulate near the DCE surface, resulting in significant interfacial clustering and adsorption at concentrations ∼0.25 m. TPB ions adsorb more strongly leading to free energy wells of ∼1-2 kBT. The adsorption modifies significantly the electrostatic potential of the DCE-air interface, which undergoes a shift of 0.2 V in going from pure DCE to TBA-TPB-DCE solutions at 0.25 m.

RESUMEN

Artificial nanomachines can be broadly defined as manmade molecular and nanosystems that are capable of performing useful tasks, very often, by means of doing mechanical work at the nanoscale. Recent advances in nanoscience allow these tiny machines to be designed and made with unprecedented sophistication and complexity, showing promise in novel applications, including molecular assemblers, self-propelling nanocarriers and in vivo molecular computation. This Feature Article overviews and compares major types of nanoscale machines, including molecular machines, self-assembled nanomachines and hybrid inorganic nanomachines, to reveal common structural features and operating principles across different length scales and material systems. We will focus on systems with feature size between 1 and 100 nm, where classical laws of physics meet those of quantum mechanics, giving rise to a spectrum of exotic physiochemical properties. Concepts of nanomachines will be illustrated by selected seminal work along with state-of-the-art progress, including our own contribution, across the fields. The Article will conclude with a brief outlook of this exciting research area.