Related Experiment Video
Updated: May 19, 2026
11:17
Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction
Published on: January 19, 2016
A crown-ether loop-derivatized oligothiophene doubly attached on gold surface as cation-binding switchable molecular
Truong Khoa Tran1, Kacem Smaali, Marie Hardouin
1LUNAM, University of Angers, CNRS UMR 6200, MOLTECH-Anjou, Group Linear Conjugated Systems, 2 Bd Lavoisier, 49045 Angers cedex, France.
Advanced Materials (Deerfield Beach, Fla.)
|August 14, 2012
Summary
A novel crown-ether dithiol quaterthiophene was developed for detecting lead ions (Pb2+). Immobilized on gold, it shows a significant current increase upon lead complexation, enabling sensitive detection.
Area of Science:
- Materials Science
- Electrochemistry
- Chemical Sensing
Background:
- Crown-ether compounds are known for ion complexation.
- Thiophene-based molecules offer unique electronic properties.
- Self-assembled monolayers on gold are widely used in sensor development.
Purpose of the Study:
- To synthesize and characterize a crown-ether dithiol quaterthiophene.
- To immobilize the molecule onto a gold surface via double covalent fixation.
- To investigate the lead ion sensing capabilities of the resulting monolayer.
Main Methods:
- Chemical synthesis of crown-ether dithiol quaterthiophene.
- Surface immobilization using double covalent fixation.
- UV-vis spectroscopy and cyclic voltammetry for characterization.
- Current-voltage measurements using eutectic GaIn drop contact.
Main Results:
- Successful synthesis and immobilization of the quaterthiophene derivative.
- Demonstration of Pb(2+) complexation in solution and on the gold surface.
- A significant increase in current (up to 1.6 × 10^3 times) observed upon Pb(2+) binding at low bias.
Conclusions:
- The developed material functions as an effective lead ion sensor.
- The sensing mechanism relies on the conformational change upon Pb(2+) complexation.
- This platform shows potential for sensitive electrochemical detection of heavy metals.
Related Concept Videos
02:36Crown Ethers
Crown ethers are cyclic polyethers that contain multiple oxygen atoms, usually arranged in a regular pattern. The first crown ether was synthesized by Charles Pederson while working at DuPont in 1967. For this work, Pedersen was co-awarded the 1987 Nobel Prize in Chemistry. Crown ethers are named using the formula x-crown-y, where x is the total number of atoms in the ring and y is the number of ether oxygen atoms. The term 'crown' refers to the crown-like shape that these ether molecules take.
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
00:57Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...
01:24Metal-Semiconductor Junctions
The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
Schottky Barriers
Schottky barriers arise when a metal with a work function (Φm) contacts a semiconductor with a different work function (Φs). Initially, electrons transfer until the Fermi levels of the metal and semiconductor align at equilibrium. For instance, if Φm > Φs, the semiconductor Fermi level is higher than the metal's before contact. The semiconductor's...
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation