nanotethers

Nanotethers are nanoscale connectors that link a nanoscale object, such as a nanoparticle, colloid, or biomolecule, to a substrate, another particle, or to a molecular handle. They serve to set a defined separation, control orientation, and provide mechanical or electrical coupling while minimizing direct contact that could perturb function. Common forms include polymer tethers (such as polyethylene glycol chains), DNA tethers formed by complementary strands, and inorganic tethers built from carbon nanotubes or silane-linked linkers. The choice of tether affects length, stiffness, biocompatibility, and tethering chemistry.

Fabrication and attachment: Tethers can be attached through surface chemistries such as silanization on oxides, thiol-gold bonding, carbodiimide coupling to carboxyl groups, or azide-alkyne cycloaddition (click chemistry). DNA tethers exploit base-pairing or aptamer binding. Grafting-to or grafting-from strategies allow control of surface density and average tether length.

Characterization and use: Techniques like atomic force microscopy, cryo-electron microscopy, fluorescence resonance energy transfer, and force spectroscopy are used to measure tether length, persistence length, and mechanical response. Nanotethers enable single-molecule force measurements, steer self-assembly, and serve as spacer arms in sensors and nanoelectronic devices.

Applications and challenges: In biosensing, nanotethers position capture elements and reduce nonspecific binding. In nanomachines, they act as compliant joints. Challenges include controlling length distribution, tether stiffness, and ensuring stability under operational conditions, as well as potential toxicity for biological applications.