Plasmon-Induced Photoreaction of o-Nitrobenzyl-Based Ligands under 550 nm Light

Abstract

We have studied the plasmon-driven photoreaction of a dual thiol-anchored o-nitrobenzyl-based photouncaging ligand on silver nanoparticles. Previous results have shown that this compound strongly anchors to gold surfaces, and a 1 J/cm 2 dose of UV light induces the intended photoreaction, uncaging an amine on the surface. This allows for photopatterning and the selective adhesion of gold nanospheres (AuNSs) to a surface via electrostatic attraction between the positively charged amines and negatively charged AuNSs. Here, we report that when the ligand is adsorbed on a silver nanospheroid film (AgNS), an additional photoreaction induced by green light inhibits AuNSs adhesion in the UV exposed film. Our findings suggest that this is a result of the neutralization of the amine group's ability to become charged, as opposed to the removal of the ligand from the surface of the silver nanospheroids. We hypothesize that this neutralization may be due to a form of hot-hole-induced photocatalysis, resulting in an NN double bond between two neighboring ligands. This reaction has been documented in similarly amine-terminated moieties. This neutralization allows for a more fine-tuned, plasmonically based control of the ligand's photoreaction, as the green light exposure only affects the ligand if it has previously been cleaved by UV light, and makes it possible to perform reverse photopatterning on the surface.

Multi-photon patterning of photoactive o-nitrobenzyl ligands bound to gold surfaces

“…61 Another possibility is that the damage is due to a secondary photoreaction in the SAM that impedes nanoparticle binding, and that we have described elsewhere. 62 One way to narrow down the range of possibilities is to investigate the timescale of the damage process, which is not clear from the data presented so far, and would vary widely depending on its precise mechanism. If the damage occurs due to a plasma-like excitation in the gold substrate or to direct heating of the SAM, involving mostly or exclusively electronic states, the damage process would be very fast, as the cooling time would be on a sub-picosecond timescale.…”

Understanding Hot-Electron Generation and Plasmon Relaxation in Metal Nanocrystals: Quantum and Classical Mechanisms

“…One convenient way to see the structure of the many-body state of a plasmon is to compute the energy distribution of electrons. 28,29 Experimentally, this topic mainly concerns two types of applications: nanomaterials for enhanced photochemistry 1,2,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]30 and photodetectors. 3,4,[21][22][23][24][25][26][27] Current literature has a large number of theoretical publications on hot plasmonic electrons.…”

“…The generation of energetic (hot) electrons in plasmonic nanostructures is currently attracting a lot of attention. − The motivations for this research topic are both fundamental and applied. It is interesting to learn more about the complexity of the plasmon’s wave function in a nanocrystal (NC).…”

“…Such wave functions involve many interacting electrons. One convenient way to see the structure of the many-body state of a plasmon is to compute the energy distribution of electrons. , Experimentally, this topic mainly concerns two types of applications: nanomaterials for enhanced photochemistry ,,− , and photodetectors. ,,− …”

Controlling the Interparticular Distances of Extended Non-Close-Packed Colloidal Monolayers

“…In turn, modifying the surface morphology, e.g., by adding long-chain alkoxy silanes instead of pure TEOS in the shell growth process, would be one route to extend the available range of distances. , Another option is tuning the chemistry of the linkage between the nanoparticle and the surface during the adsorption step using instead of weak dispersive interactions, as in the present study, more covalent linkages between the nanoparticles and a suitably functionalized surface . It is also possible to think of adding an anchoring step after the assembly of the particles, which is possible if functionalized metal surfaces capable of covalently linking the particles to the surface after assembly are used, for example, using photoinduced tethering. , Hence, taking appropriate measures to prevent the deterioration of spatial order by capillary forces during drying, it is expected that one can exploit the full range of possible ionic strengths for adjusting the interparticle distances in non-close-packed nanoparticle arrays. Following the calculation based on an effective hard-sphere model shown in Figure B, which corresponds well with our experimental data for lower ionic strengths, for the present particle system, this corresponds to a coverage limit slightly above 0.4.…”