Cation-induced pesticide binding and release by a functionalized calix[4]arene molecular host

Fluorescence-Based Sensing of Pesticides Using Supramolecular Chemistry

The detection of pesticides in real-world environments is a high priority for a broad range of applications, including in areas of public health, environmental remediation, and agricultural sustainability. While many methods for pesticide detection currently exist, the use of supramolecular fluorescence-based methods has significant practical advantages. Herein, we will review the use of fluorescence-based pesticide detection methods, with a particular focus on supramolecular chemistry-based methods. Illustrative examples that show how such methods have achieved success in real-world environments are also included, as are areas highlighted for future research and development.

Switching Ion Binding Selectivity of Thiacalix[4]arene Monocrowns at Liquid-Liquid and 2D-Confined Interfaces

Understanding the interaction of ions with organic receptors in confined space is of fundamental importance and could advance nanoelectronics and sensor design. In this work, metal ion complexation of conformationally varied thiacalix[4]monocrowns bearing lower-rim hydroxy (type I), dodecyloxy (type II), or methoxy (type III) fragments was evaluated. At the liquid–liquid interface, alkylated thiacalixcrowns-5(6) selectively extract alkali metal ions according to the induced-fit concept, whereas crown-4 receptors were ineffective due to distortion of the crown-ether cavity, as predicted by quantum-chemical calculations. In type-I ligands, alkali-metal ion extraction by the solvent-accessible crown-ether cavity was prevented, which resulted in competitive Ag⁺ extraction by sulfide bridges. Surprisingly, amphiphilic type-I/II conjugates moderately extracted other metal ions, which was attributed to calixarene aggregation in salt aqueous phase and supported by dynamic light scattering measurements. Cation–monolayer interactions at the air–water interface were monitored by surface pressure/potential measurements and UV/visible reflection–absorption spectroscopy. Topology-varied selectivity was evidenced, towards Sr²⁺ (crown-4), K⁺ (crown-5), and Ag⁺ (crown-6) in type-I receptors and Na⁺ (crown-4), Ca²⁺ (crown-5), and Cs⁺ (crown-6) in type-II receptors. Nuclear magnetic resonance and electronic absorption spectroscopy revealed exocyclic coordination in type-I ligands and cation–π interactions in type-II ligands.

Controlled binding of organic guests by stimuli-responsive macrocycles

Synthetic supramolecular chemistry pursues not only the construction of new matter, but also control over its inherently dynamic behaviour.

Rational Design of Efficient Environmental Sensors: Ring-Shaped Nanostructures Can Capture Quat Herbicides

The viability of using [n]-cycloparaphenylenes (CPPs) of different sizes to encapsulate diquat (DQ) pesticide molecules has been tested analyzing the origin of the host-guest interactions stabilizing the complex. This analysis provides rational design capabilities to construct ad hoc capturing systems tailored to the desired pollutant. All CPPs considered (n = 7-12) are capable of forming remarkably stable complexes with DQ, though [9]-CPP is the best candidate, where a fine balance is established between the energy penalty due to the deformation + repulsion of the pesticide molecule inside the cavity (larger in smaller CPPs) and the maximization of the favorable dispersion, electrostatic and induction contributions (which also decrease in larger rings). These encouraging results prompted us to evaluate the potential of using Resonance Raman spectroscopy on nanohoop complexes as a tool for DQ sensing. The shifts observed in the vibrational frequencies of DQ upon complexation allow us to determine whether complexation has been achieved. Additionally, a large enhancement of the signals permits a selective identification of the vibrational modes.

Promoting Lubricity and Antifouling Properties by Supramolecular-Recognition-Based Surface Grafting

In the supramolecular host-guest system, the host molecule selectively identifies the guest and forms the inclusion complex with the guest molecule. In this study, the physicochemical properties of solid surfaces were regulated by the interfacial supramolecular recognition. The host-guest interaction between β-cyclodextrin and guest molecules, including adamantaneacetic acid, sodium dodecyl sulfonate, and a copolymer of 2-methacryloyloxy-2-methyladamantane and 3-sulfopropyl methacrylate potassium salt, was introduced onto the silicon substrate to construct supramolecular composite surfaces. After the assembly of hydrophilic guest molecules on the host surface, the wettability, aqueous lubrication, and anti-algae cell adhesion properties of the supramolecular composite surfaces were improved. This strategy of host-guest interfacial supramolecular recognition provides a new route to prepare aqueous lubrication and antifouling materials.

Pesticide binding and urea-induced controlled release applications with calixarene naphthalimide molecules by host-guest complexation

Three novel calix[4]arene molecule-based 1,8 naphthalimide fluoroionophore for the selective determination of kesoxim-methyl were synthesized and used in pesticide binding studies. The possible interaction between pesticides and fluorescent calix[4]arene molecules was monitored by UV/Vis absorption and fluorescence spectroscopy. When compared the studied pesticides, kesoxim-methyl was strongly quenched the fluorescence intensity of upper rim-modified calix[4]arene. UV and fluorescence titration experiments were also studied to determine both the quenching mechanism and stoichiometric ratio consisted in complex formation. Furthermore, pesticide release experiments were also performed with a fertilizing agent as urea by using fluorescence spectroscopy technique.

A photo-responsive macroscopic switch constructed using a chiral azo-calix[4]arene functionalized silicon surface

A photo-responsive macroscopic switch was fabricated using a chiral azo-calix[4]arene derivative (FC4AD) functionalized silicon surface and exhibited selective and reversible recognition of (1R,2S)-1-amino-2-indanol through the variation of wettability.

Macroscopic switches constructed through host–guest chemistry

In this feature article, we discuss recent developments in macroscopic contact angle switches formed by different macrocyclic hosts and highlight the properties of these new functional surfaces and their potential applications.

Calix[4]arene triazole-linked pyrene: click synthesis, assembly on graphene oxide, and highly sensitive carbaryl sensing in serum

Graphene oxide modified with a fluorescent calix[4]arene showed a highly selective recognition for carbaryl.