Chiral plasmonic metal nanoparticles (Months 1–24)
Plan: Seed-mediated, amino-acid/peptide–directed asymmetric overgrowth to generate helicoidal/twisted surface features; target strong CD and tunable plasmon bands. (Maps to D1.).
Results:
- Reproduced and adapted chiral growth using small-molecule enantiomers (e.g. chiral diamine and cysteine family) and mixed-surfactant systems; established parameter windows (metal precursor: chiral-inducer ratio; reducer/surfactant balance) for reliable chirality transfer.
- Produced libraries of chiral Au nanostructures (including wrinkled Au-NR–based systems) with plasmon resonances from visible to NIR; achieved stable, sign-consistent CD with g-factors approaching literature benchmarks for wrinkled Au NRs.
2D Plasmene nanosheets (Months 3–24)
Plan: Assemble (chiral) Au NPs into ordered superlattices/monolayers for chiroptical readout and SERS. Template-assisted and liquid–liquid interfacial self-assembly.
Results:
Two routes were used. (A) Template-assisted: to yield ordered mm-scale superlattices suitable for controlled collective CD. The structural integrity of the 2D superlattices was characterized by SEM. The well-ordered superlattices, with precise tip-to-tip alignment, enabled us to disentangle the intrinsic CD of individual chiral NRs from the extrinsic surface lattice resonance-induced response of the arrays. (B) Liquid–liquid interfacial: to yield continuous, closely packed monolayers with cm-scale uniformity with the CD response of the 2D plasmene sheets can be up to 1.2 (Figure 3). The structural integrity of the 2D plasmene sheets was characterized by SEM and they are compatible with flexible supports and optical/SERS.
Structural & chiroptical characterization + modelling (M4–M22)
Plan: Correlate structure–property (electron microscopy and tomography), quantify true CD on solids (Mueller-matrix), establish SERS, and guide design by modelling.
Results:
-Microscopy: SEM on assemblies; selective HR-STEM/tomography quantified wrinkled morphology.
-Mueller-matrix (IPF Dresden): Training + measurements completed; LD/LB artifacts removed; incidence-angle protocols (ICMAB) established to separate intrinsic vs extrinsic CD.
-Raman: Baseline SERS validated; SEROA initiated with circular-polarization control (optimization ongoing).
-Modelling: Owing to the prohibitive complexity of wrinkled chiral geometries, FDTD was limited to single-nanoparticle models (no superlattice/monolayer). These simulations assigned resonances, mapped chiral near fields, and yielded qualitative design rules (e.g. gap/orientation targets) that informed WP1b; assembly-level effects were interpreted experimentally.
Flexible SERS substrates & biomarker detection (Months 8–24)
Plan: Fabricate PDMS-supported, flexible chiral plasmene/array substrates; quantify SERS performance; demonstrate biomarker (melanoma, breast cancer) detection and chirality discrimination. (Maps to D3; reaches M2.)
Deviation: The planned PS–thiol plasmene route formed a dense Au passivation layer that blocked analyte adsorption, incompatible with SERS hot-spot access.
Corrective strategy:
(i) Template-assisted arrays without PS–SH: CTAC-stabilized (chiral) Au NPs patterned on solid glass/PDMS substrate; brief UV–ozone then low-dose O2 plasma removed surfactants and exposed Au while preserving order.
(ii) Liquid–liquid interfacial self-assembled monolayers with post-transfer deprotection: assemble first, then UV–ozone → rinse → O2 plasma to restore adsorption-competent Au.
(iii) Access controls: rapid 4-MBA binding as internal standard, amino-acid tests in buffer, and blank-substrate checks verified clean baselines.
Outcome. The revised workflow yields flexible, reproducible SERS films. Pilot measurements for chirality-sensitive readouts were initiated (Figure 4). Biomarker detection was not completed; only preliminary amino-acid discrimination was demonstrated during the reporting period. Consequently, D3 is partially achieved, with full analytical validation deferred beyond the project.
