Periodic Reporting for period 1 - SURF-CHIR (Covalent chiral functionalization of graphite for enantioselective applications)
Período documentado: 2024-01-01 hasta 2025-12-31
Resumen del contexto y de los objetivos generales del proyecto
Many of the molecules essential to life — including amino acids, sugars, and DNA — exist in two mirror-image forms, like left and right hands. This property is called chirality. In chemistry and medicine, the two mirror-image versions of a molecule (enantiomers) can behave very differently: one may be a useful drug, while the other is inactive or even harmful. The ability to distinguish, separate, and exploit chirality is therefore of fundamental importance to the pharmaceutical, chemical, and materials industries.
At the same time, a separate but related challenge is emerging in electronics. As conventional silicon-based devices approach their physical size limits, scientists are exploring molecules as the active components of next-generation electronic devices. One promising phenomenon is the chirality-induced spin selectivity (CISS) effect: chiral molecules can act as filters for electron spin — the quantum property that underlies magnetic data storage and quantum computing technologies. Harnessing CISS in practical devices could open new routes to room-temperature molecular spintronics, with applications in data storage, sensing, and quantum information.
The SURF-CHIR project was designed to address both of these challenges through a single unified approach: the fabrication of functional chiral surfaces. The project was carried out at KU Leuven (Belgium) under the Marie Skłodowska-Curie Postdoctoral Fellowship programme, which supports the career development of excellent researchers while advancing European scientific priorities in nanotechnology and advanced materials.
The original objectives of the project were to: (1) create stable chiral surfaces by chemically attaching chiral molecules to carbon-based materials; (2) use these surfaces to achieve enantioselective adsorption — the preferential capture of one mirror-image form of a molecule over the other; and (3) scale up the approach for practical applications in chiral separation and chromatography. Together, these objectives were designed to contribute to more efficient production of enantiopure drugs, greener chemical synthesis, and a deeper understanding of chirality at the nanoscale.
As the project evolved, the scientific pathway shifted toward physisorption-based chiral surfaces and their application in molecular spintronics — an outcome that proved more impactful than originally anticipated, delivering results that challenge long-standing assumptions in the field and open new directions for both surface science and spintronic device design.
At the same time, a separate but related challenge is emerging in electronics. As conventional silicon-based devices approach their physical size limits, scientists are exploring molecules as the active components of next-generation electronic devices. One promising phenomenon is the chirality-induced spin selectivity (CISS) effect: chiral molecules can act as filters for electron spin — the quantum property that underlies magnetic data storage and quantum computing technologies. Harnessing CISS in practical devices could open new routes to room-temperature molecular spintronics, with applications in data storage, sensing, and quantum information.
The SURF-CHIR project was designed to address both of these challenges through a single unified approach: the fabrication of functional chiral surfaces. The project was carried out at KU Leuven (Belgium) under the Marie Skłodowska-Curie Postdoctoral Fellowship programme, which supports the career development of excellent researchers while advancing European scientific priorities in nanotechnology and advanced materials.
The original objectives of the project were to: (1) create stable chiral surfaces by chemically attaching chiral molecules to carbon-based materials; (2) use these surfaces to achieve enantioselective adsorption — the preferential capture of one mirror-image form of a molecule over the other; and (3) scale up the approach for practical applications in chiral separation and chromatography. Together, these objectives were designed to contribute to more efficient production of enantiopure drugs, greener chemical synthesis, and a deeper understanding of chirality at the nanoscale.
As the project evolved, the scientific pathway shifted toward physisorption-based chiral surfaces and their application in molecular spintronics — an outcome that proved more impactful than originally anticipated, delivering results that challenge long-standing assumptions in the field and open new directions for both surface science and spintronic device design.
Trabajo realizado desde el comienzo del proyecto hasta el final del período abarcado por el informe y los principales resultados hasta la fecha
Work Performed and Main Achievements
Creating Functional Chiral Surfaces: The project began by attempting to chemically attach chiral molecules directly onto graphite surfaces using a light-activated reaction (nitrene cycloaddition chemistry). Despite extensive optimisation of reaction conditions, this approach did not produce a sufficiently dense or ordered chiral layer on the graphite surface — a challenge that had been anticipated in the project's risk plan. In response, the project pivoted to a different strategy: allowing chiral molecules to organise themselves spontaneously on gold surfaces through self-assembly. This approach proved highly effective and ultimately led to richer scientific outcomes than the original route.
Two molecular systems were investigated. The first used enantiopure organic semiconductor molecules (DNTT derivatives) carrying chiral side chains. When deposited onto a gold surface, these molecules spontaneously arranged into highly ordered, mirror-image networks — one forming a clockwise pattern, the other counterclockwise — as confirmed by scanning tunnelling microscopy (STM). The second system used a racemic mixture (equal amounts of both mirror-image forms) of a helical organic molecule (BTBT derivative). Remarkably, rather than forming a disordered mixed layer, the two enantiomers spontaneously separated on the gold surface into distinct homochiral domains — a process known as surface-assisted symmetry breaking. Both systems produced well-defined chiral surfaces suitable for functional measurements.
Discovering New Rules for Spin Filtering: The chiral surfaces were studied using scanning tunnelling spectroscopy (STS) on specialised magnetic substrates, allowing the spin-filtering properties of each surface to be measured directly at the nanoscale. The results produced two significant and unexpected findings.
First, the DNTT-based surfaces — despite being made from flat, non-helical molecules — showed spin-filtering efficiency (measured as enantiospecific magnetic conductance asymmetry, EMA) exceeding 40% at room temperature. This is among the highest values reported for any molecular system. Prior to this work, it was widely believed that a helical three-dimensional molecular structure was necessary for spin filtering. This result demonstrates for the first time that two-dimensional organisational chirality — the way flat molecules arrange themselves collectively on a surface — is sufficient to generate strong spin selectivity.
Second, the racemic BTBT system showed that the spontaneously formed homochiral domains each produced spin-filtering efficiency of around 35% at room temperature. This is the first demonstration that a globally achiral (racemic) molecular system can act as a spin filter, made possible by the local chirality of the self-organised surface domains. Three independent control experiments confirmed that these effects are genuine and not measurement artefacts.
Enantioselective Adsorption: In parallel, the project investigated whether chiral surfaces or chiral molecules in solution could selectively favour the adsorption of one mirror-image molecular form over the other. Using a chiral auxiliary molecule (DM8OCB) added to a solution of a prochiral liquid crystal (12CB), a statistically significant bias in surface domain handedness was demonstrated: approximately 69% of domains adopted the preferred handedness when the chiral auxiliary was present, compared to the expected 50/50 baseline. This confirms that chiral induction from solution is an effective and non-invasive route to enantioselective surface assembly.
Summary of Key Outcomes
The project delivered two peer-reviewed publications. The first, published in the Journal of the American Chemical Society (2025), reports the first observation of CISS in a non-helical two-dimensional molecular system. The second, currently under review, reports the first observation of CISS in a globally achiral racemic system. Together, these results establish new design principles for spin-filtering molecular materials and open synthetic routes to CISS-active surfaces that do not require complex enantiopure starting materials.
Creating Functional Chiral Surfaces: The project began by attempting to chemically attach chiral molecules directly onto graphite surfaces using a light-activated reaction (nitrene cycloaddition chemistry). Despite extensive optimisation of reaction conditions, this approach did not produce a sufficiently dense or ordered chiral layer on the graphite surface — a challenge that had been anticipated in the project's risk plan. In response, the project pivoted to a different strategy: allowing chiral molecules to organise themselves spontaneously on gold surfaces through self-assembly. This approach proved highly effective and ultimately led to richer scientific outcomes than the original route.
Two molecular systems were investigated. The first used enantiopure organic semiconductor molecules (DNTT derivatives) carrying chiral side chains. When deposited onto a gold surface, these molecules spontaneously arranged into highly ordered, mirror-image networks — one forming a clockwise pattern, the other counterclockwise — as confirmed by scanning tunnelling microscopy (STM). The second system used a racemic mixture (equal amounts of both mirror-image forms) of a helical organic molecule (BTBT derivative). Remarkably, rather than forming a disordered mixed layer, the two enantiomers spontaneously separated on the gold surface into distinct homochiral domains — a process known as surface-assisted symmetry breaking. Both systems produced well-defined chiral surfaces suitable for functional measurements.
Discovering New Rules for Spin Filtering: The chiral surfaces were studied using scanning tunnelling spectroscopy (STS) on specialised magnetic substrates, allowing the spin-filtering properties of each surface to be measured directly at the nanoscale. The results produced two significant and unexpected findings.
First, the DNTT-based surfaces — despite being made from flat, non-helical molecules — showed spin-filtering efficiency (measured as enantiospecific magnetic conductance asymmetry, EMA) exceeding 40% at room temperature. This is among the highest values reported for any molecular system. Prior to this work, it was widely believed that a helical three-dimensional molecular structure was necessary for spin filtering. This result demonstrates for the first time that two-dimensional organisational chirality — the way flat molecules arrange themselves collectively on a surface — is sufficient to generate strong spin selectivity.
Second, the racemic BTBT system showed that the spontaneously formed homochiral domains each produced spin-filtering efficiency of around 35% at room temperature. This is the first demonstration that a globally achiral (racemic) molecular system can act as a spin filter, made possible by the local chirality of the self-organised surface domains. Three independent control experiments confirmed that these effects are genuine and not measurement artefacts.
Enantioselective Adsorption: In parallel, the project investigated whether chiral surfaces or chiral molecules in solution could selectively favour the adsorption of one mirror-image molecular form over the other. Using a chiral auxiliary molecule (DM8OCB) added to a solution of a prochiral liquid crystal (12CB), a statistically significant bias in surface domain handedness was demonstrated: approximately 69% of domains adopted the preferred handedness when the chiral auxiliary was present, compared to the expected 50/50 baseline. This confirms that chiral induction from solution is an effective and non-invasive route to enantioselective surface assembly.
Summary of Key Outcomes
The project delivered two peer-reviewed publications. The first, published in the Journal of the American Chemical Society (2025), reports the first observation of CISS in a non-helical two-dimensional molecular system. The second, currently under review, reports the first observation of CISS in a globally achiral racemic system. Together, these results establish new design principles for spin-filtering molecular materials and open synthetic routes to CISS-active surfaces that do not require complex enantiopure starting materials.
Avances que van más allá del estado de la técnica e impacto potencial esperado (incluida la repercusión socioeconómica y las implicaciones sociales más amplias del proyecto hasta la fecha)
Results Beyond the State of the Art
What Was Known Before SURF-CHIR
The ability of chiral molecules to filter electron spin — the CISS effect — had been established in the years prior to this project, primarily in biological molecules such as DNA and peptides, and in synthetic helical molecules called helicenes. The scientific community had converged on two widely accepted assumptions: first, that a three-dimensional helical molecular structure was necessary to generate spin filtering; and second, that only enantiopure (single mirror-image) materials could be used, since mixing both mirror-image forms was expected to cancel any spin-filtering effect. These assumptions were significantly limiting the range of materials considered useful for molecular spintronic applications.
What SURF-CHIR Demonstrated
SURF-CHIR produced two results that directly overturn both of these assumptions.
Flat molecules can filter spin. By studying self-assembled layers of flat organic semiconductor molecules (DNTT derivatives) on magnetic surfaces, the project demonstrated spin-filtering efficiency above 40% at room temperature — without any helical molecular geometry. The chirality responsible for this effect arises entirely from the way the flat molecules arrange themselves collectively on the surface, forming a two-dimensional chiral pattern. This is the first time CISS has been unambiguously demonstrated in a non-helical system, and it establishes a completely new design principle: the collective packing geometry of a molecular layer matters as much as — or more than — the shape of individual molecules.
Racemic mixtures can act as spin filters. The project demonstrated for the first time that a racemic mixture — containing equal amounts of both mirror-image forms of a molecule — can produce strong spin filtering (around 35% efficiency at room temperature) when the two forms spontaneously separate into distinct domains on a surface. This surface-assisted symmetry breaking generates local chirality even from a globally achiral starting material. This finding removes a fundamental synthetic barrier: producing enantiopure molecules requires complex and costly asymmetric chemistry, whereas racemic mixtures can often be made in a single straightforward step.
Potential Impacts
These results have potential relevance across several areas.
Molecular spintronics and data storage. Spin-filtering molecular layers are of interest for next-generation data storage, magnetic sensing, and quantum information technologies. The demonstration that cheap, easily synthesised flat organic semiconductors — a materials class already used in organic electronics and display technologies — can serve as spin filters substantially broadens the practical toolkit available to device engineers.
Green and accessible chemistry. The finding that racemic mixtures can generate functional chiral surfaces reduces the need for expensive enantioselective synthesis, potentially lowering the cost and environmental footprint of producing spintronic materials.
Chiral separation and sensing. The chiral auxiliary results from the project contribute to understanding how surface chirality can be induced and controlled without covalent modification, which is relevant to the design of sensors and separation platforms for the pharmaceutical industry.
What Is Needed for Further Uptake
Translating these fundamental findings into practical applications will require further work in several areas. Additional research is needed to understand how CISS efficiency scales with domain size, molecular layer thickness, and substrate architecture, and to identify the best molecular candidates for device integration. Demonstration of spin-filtering function in solid-state device geometries — beyond the scanning probe measurements used in this project — is a key next step. Access to specialised ferromagnetic substrate fabrication facilities and synthetic chemistry partnerships will be important for this, as will continued international collaboration between surface science, synthetic chemistry, and device engineering communities. The findings also provide a strong scientific foundation for follow-on funding applications, including European Research Council grants, which would enable the transition from fundamental discovery to applied demonstration.
What Was Known Before SURF-CHIR
The ability of chiral molecules to filter electron spin — the CISS effect — had been established in the years prior to this project, primarily in biological molecules such as DNA and peptides, and in synthetic helical molecules called helicenes. The scientific community had converged on two widely accepted assumptions: first, that a three-dimensional helical molecular structure was necessary to generate spin filtering; and second, that only enantiopure (single mirror-image) materials could be used, since mixing both mirror-image forms was expected to cancel any spin-filtering effect. These assumptions were significantly limiting the range of materials considered useful for molecular spintronic applications.
What SURF-CHIR Demonstrated
SURF-CHIR produced two results that directly overturn both of these assumptions.
Flat molecules can filter spin. By studying self-assembled layers of flat organic semiconductor molecules (DNTT derivatives) on magnetic surfaces, the project demonstrated spin-filtering efficiency above 40% at room temperature — without any helical molecular geometry. The chirality responsible for this effect arises entirely from the way the flat molecules arrange themselves collectively on the surface, forming a two-dimensional chiral pattern. This is the first time CISS has been unambiguously demonstrated in a non-helical system, and it establishes a completely new design principle: the collective packing geometry of a molecular layer matters as much as — or more than — the shape of individual molecules.
Racemic mixtures can act as spin filters. The project demonstrated for the first time that a racemic mixture — containing equal amounts of both mirror-image forms of a molecule — can produce strong spin filtering (around 35% efficiency at room temperature) when the two forms spontaneously separate into distinct domains on a surface. This surface-assisted symmetry breaking generates local chirality even from a globally achiral starting material. This finding removes a fundamental synthetic barrier: producing enantiopure molecules requires complex and costly asymmetric chemistry, whereas racemic mixtures can often be made in a single straightforward step.
Potential Impacts
These results have potential relevance across several areas.
Molecular spintronics and data storage. Spin-filtering molecular layers are of interest for next-generation data storage, magnetic sensing, and quantum information technologies. The demonstration that cheap, easily synthesised flat organic semiconductors — a materials class already used in organic electronics and display technologies — can serve as spin filters substantially broadens the practical toolkit available to device engineers.
Green and accessible chemistry. The finding that racemic mixtures can generate functional chiral surfaces reduces the need for expensive enantioselective synthesis, potentially lowering the cost and environmental footprint of producing spintronic materials.
Chiral separation and sensing. The chiral auxiliary results from the project contribute to understanding how surface chirality can be induced and controlled without covalent modification, which is relevant to the design of sensors and separation platforms for the pharmaceutical industry.
What Is Needed for Further Uptake
Translating these fundamental findings into practical applications will require further work in several areas. Additional research is needed to understand how CISS efficiency scales with domain size, molecular layer thickness, and substrate architecture, and to identify the best molecular candidates for device integration. Demonstration of spin-filtering function in solid-state device geometries — beyond the scanning probe measurements used in this project — is a key next step. Access to specialised ferromagnetic substrate fabrication facilities and synthetic chemistry partnerships will be important for this, as will continued international collaboration between surface science, synthetic chemistry, and device engineering communities. The findings also provide a strong scientific foundation for follow-on funding applications, including European Research Council grants, which would enable the transition from fundamental discovery to applied demonstration.