Introduction

Chirality—the “handedness” of molecules—is a universal phenomenon in nature, from the double helix of DNA to the α-helices of proteins. In materials science, efficiently transferring molecular chirality to macroscopic scales and amplifying chiroptical signals has long been a pursuit of scientists.

Recently, Professor Chuan-Liang Feng’s research group at Shanghai Jiao Tong University published a breakthrough study in Advanced Materials. They proposed a novel “sub-stoichiometric supramolecular co-assembly” strategy, using only a trace amount (0.2 equivalents) of the natural small molecule berberine (BBR) to achieve efficient chirality transfer and significant amplification of circularly polarized luminescence (CPL).

This discovery overturns conventional wisdom—efficient chirality transfer does not necessarily require large amounts of “chiral inducers” ; precise stoichiometric control is the key.

The Challenge with Traditional Approaches

In conventional supramolecular co-assembly systems, stoichiometric or even excess guest loading is typically required for effective chirality transfer. However, this strategy has significant drawbacks:

1. Equimolar co-assembly can form well-defined structures but often results in rigidity that limits chiral amplification and adaptive responses.

2. Excess guest molecules disrupt the delicate balance of noncovalent interactions, driving transitions from ordered 1D nanostructures to disordered 0D aggregates, causing aggregation-caused quenching (ACQ) that compromises both luminescence efficiency and CPL performance.

Maintaining the structural integrity of the host framework while achieving efficient chirality transfer and enhanced luminescence has been a long-standing challenge in the field.

Key Finding: 0.2 Equivalents of Guest—A “Less is More” Breakthrough

The research team cleverly selected berberine (BBR) —a natural isoquinoline alkaloid with aggregation-induced emission (AIE) properties extracted from Chinese herbal plants—as the achiral guest modulator. They found that:

• At a BBR-to-gelator molar ratio of just 0.2, the system forms stable hydrogels with intense yellow-green luminescence.

• The hydrogels exhibit a remarkably high luminescence dissymmetry factor of |g_lum| ≈ 0.08—an order of magnitude higher than stoichiometric equivalents and significantly surpassing most reported organic supramolecular CPL systems.

• SEM images reveal that 0.2 equivalents of BBR induce well-defined left-handed (M-type) and right-handed (P-type) helical nanofiber bundles, while increasing the BBR ratio to 1.0 equivalent disrupts the helical structure, resulting in disordered nanofiber networks.

Mechanistic Insights: Why Does “Less” Mean “More”?

Why does a trace amount of guest work better? Through single-crystal X-ray diffraction, spectroscopy, and molecular dynamics simulations, the team uncovered the underlying mechanism:

At the sub-stoichiometric condition (LBR-0.2) :

• BBR molecules sparsely intercalate into the chiral gel framework, fully preserving the underlying hydrogen-bonded network.

• Through synergistic π–π stacking and electrostatic interactions, BBR is precisely “anchored” into the helical registry, achieving ordered helical arrangement.

• This ordered arrangement not only ensures thermodynamic stability (ΔG° = -56.49 kJ/mol) but also significantly enhances BBR’s fluorescence emission through the AIE mechanism.

When BBR is in excess (LBR-1) :

• Excess BBR disrupts the LPF-LPF hydrogen-bonding “ladders,” causing the helical structure to collapse.

• The system falls into a “kinetically trapped” state, forming non-helical aggregates with diminished chiroptical activity.

• Although a higher enthalpic gain (ΔH°) is achieved, a significant entropic penalty (ΔS°) results in a less favorable Gibbs free energy (ΔG° = -35.51 kJ/mol).

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Applications: From Anti-Counterfeiting to Information Encryption

Leveraging the efficient CPL properties, the team demonstrated the hydrogels’ great potential in information encryption and anti-counterfeiting:

1. Multimodal optical encryption: Information is hidden under daylight; under UV, all regions emit fluorescence, creating misleading output; only under left-handed CPL does the correct information (e.g., “2026”) emerge.

2. QR code anti-counterfeiting system: QR positioning squares and information modules are coated with hydrogels of opposite handedness. Under UV, the QR code is scannable (first-level authentication); under CPL, specific regions are selectively quenched, rendering the QR code unreadable (second-level authentication), providing robust protection against replication.

3. Reversible write-erase: Acid/base stimuli enable reversible fluorescence switching, supporting multiple encryption-decryption cycles with 87.60% performance retention.

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Conclusion

This study reveals a profound scientific insight: in supramolecular chemistry, “less” can indeed be “more.” Through precise stoichiometric control, just 0.2 equivalents of a natural small molecule can leverage the entire supramolecular system for chiral amplification. This nature-inspired “sub-stoichiometric” co-assembly paradigm transcends conventional doping strategies, bypassing kinetic traps and achieving high-fidelity chirality through stoichiometric tuning and cooperative noncovalent interactions. It opens new avenues for the design of high-performance chiroptical materials and holds promise for applications in smart anti-counterfeiting, 3D displays, and photoelectronic devices.

Original paper: Sravan Baddi, Fengli Gao, et al. “Sub-Stoichiometric Supramolecular Co-Assembly Strategy Enabling Efficient Chirality Transfer and CPL Amplification.” Advanced Materials, 2026. 

https://doi.org/10.1002/adma.74767Digital Object Identifier (DOI)