Self-assembled 2D Chiral Plasmene Nanosheets for Biomarker Detection Based on Surface-Enhanced Raman Scattering

Project Information

ChirPlasBiosensing

Grant agreement ID: 101108659

DOI

10.3030/101108659

Project closed

EC signature date 27 April 2023

Start date 1 November 2023

End date 31 October 2025

Funded under

• Marie Skłodowska-Curie Actions (MSCA)

Total cost

No data

EU contribution

€ 181 152,96

Coordinated by

ASOCIACION CENTRO DE INVESTIGACION COOPERATIVA EN BIOMATERIALES- CIC biomaGUNE
Spain

Periodic Reporting for period 1 - ChirPlasBiosensing (Self-assembled 2D Chiral Plasmene Nanosheets for Biomarker Detection Based on Surface-Enhanced Raman Scattering)

Reporting period: 2023-11-01 to 2025-10-31

Summary of the context and overall objectives of the project

Self-assemble 2D chiral plasmene nanosheets: ultrasensitive biomarker and chirality detectors.
Surface plasmons are coherent and collective electron oscillations along the surface of a metal. In the case of plasmonic metal nanoparticles, this collective oscillation of conduction electrons yields remarkable optical properties that can be tuned under the right conditions. With the support of the Marie Skłodowska-Curie Actions programme, the ChirPlasBiosensing project aimed to develop a novel functional chiral plasmonic biosensing platform from self-assembled 2D chiral plasmene nanosheets. The 2D plasmene nanosheets (one-particle-thick superlattices of plasmonic nanoparticles) were formed from colloidal chiral plasmonic nanoparticles of different morphologies and optimised chiroptical responses. These nanoparticles were synthesised via chirality transfer from soft chiral growth-directing molecules such as amino acids and peptides.

During the execution of the project, chemical methods were developed to synthesize colloidal chiral plasmonic nanoparticles and assemble them into 2D plasmene nanosheets. Chiral components on the surface of metal nanocrystals enantioselectively interact with chiral growth-directing molecules, such as amino acids and peptides, leading to the asymmetric evolution of chiral plasmonic metal nanoparticles. The chirality transfer from soft chiral molecules to inorganic metal surfaces derive from the highly twisted surface features on the nanoparticles induced by the chiral molecules during overgrowth. Chiral plasmonic nanoparticles with different morphologies were synthesized, their interparticle spacings and orientation were adjusted, and finally their chiroptical responses were optimized. Highly chiral 2D graphene-like plasmonic superlattices, or plasmene nanosheets, were then fabricated on flexible substrates to serve as all-hot-spot practical chiral sensing platforms via control over interparticle spacing and orientation. A novel functional chiral plasmonic biosensing platform was constructed by the self-assembled 2D chiral plasmene nanosheets, based on surface-enhanced Raman scattering, for ultrasensitive biomarker detection and chirality discrimination.

The action set out to (O1) develop chemical methods for the scalable synthesis of high-quality colloidal chiral plasmonic metal nanoparticles; (O2) construct 2D chiral plasmene nanosheets based on the individual chiral nanoparticles for enhanced optical chirality; and (O3) construct flexible SERS substrates based on 2D chiral plasmene nanosheets for ultrasensitive biomarker detection and chirality discrimination.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

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.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The project has made substantial progress toward delivering scientific impact in the field of chiral plasmonic nanomaterials and light–matter interactions. The synthesis and self-assembly of chiral plasmonic nanorods into well-defined linear and two-dimensional architectures have advanced the understanding of how nanoscale chirality translates into macroscopic optical responses. By correlating structural parameters (aspect ratio, interparticle spacing, and orientation) with chiroptical properties obtained from circular dichroism (CD) and SEROA spectroscopy, the project has contributed new insights into the mechanisms underlying plasmonic chirality amplification.

While the project is primarily fundamental, its findings lay groundwork for future industrial exploitation. The demonstrated design principles for large-area chiral plasmonic assemblies could inspire scalable fabrication of SERS substrates, optical filters, and enantioselective sensors. Potential collaborations with material developers and diagnostic companies could be envisaged in follow-up projects, particularly within the EU’s strategic priorities in advanced materials and health technologies.

The development of this type of detection technologies will have a positive impact on the biomedical industry, creating new lines of business and contributing to the economic growth of this industrial sector.