Electric Polarization-Dependent Absorption and Photocurrent Generation in Limnospira indica Immobilized on Boron-Doped Diamond
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-07-17 |
| Journal | ACS Omega |
| Authors | Nikolay V. Ryzhkov, Nora Colson, Essraa Ahmed, Paulius Pobedinskas, Ken Haenen |
| Institutions | Swiss Federal Laboratories for Materials Science and Technology, Belgian Nuclear Research Centre |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Electric Polarization-Dependent Absorption and Photocurrent Generation in Limnospira indica Immobilized on Boron-Doped Diamond
Section titled âTechnical Documentation & Analysis: Electric Polarization-Dependent Absorption and Photocurrent Generation in Limnospira indica Immobilized on Boron-Doped DiamondâExecutive Summary
Section titled âExecutive SummaryâThis research validates the critical role of Boron-Doped Diamond (BDD) as a high-performance, biocompatible current collector for biophotoelectrochemical cells (BPECs) utilizing live cyanobacteria.
- Core Material Validation: MPCVD-grown BDD thin films (180 nm thick) were successfully used as semiconducting electrodes for immobilizing Limnospira indica (P6) cyanobacteria.
- High-Density Doping: The BDD synthesis utilized a high B/C ratio (20,000 ppm) via MPCVD at 730 °C, confirming the need for heavily doped diamond to achieve efficient charge transfer.
- Polarization Effect: External electrical polarization significantly modulated the light absorption characteristics of the cyanobacteria, demonstrating a direct causal relationship between the electric field and photosynthetic properties.
- Enhanced Absorption: Negative polarization (-0.6 V vs Ag/AgCl) resulted in a substantial increase (up to 12%) in light absorbance, particularly in the green-red spectrum, opening avenues for biophotocathode optimization.
- Superior Performance: The BDD electrode paired with the conductive polymer PEDOT:PSS showed superior charge flow and conductivity compared to agar hydrogel matrices.
- Photocurrent Generation: The BDD/PEDOT/PSS biophotoelectrode demonstrated efficient cathodic photocurrent generation, utilizing the entire visible spectrum, with maximum output under UV light (375 nm).
- Application Focus: The findings are crucial for the rational design and optimization of regenerative life support systems and durable self-sustaining environments for space travel and colonization.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the MPCVD synthesis and electrochemical testing described in the paper.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Material | BDD Thin Film | N/A | Boron-Doped Diamond |
| Film Thickness | 180 | nm | Deposited on fused silica substrate |
| Substrate Dimensions | 40 x 10 | mm | Fused silica |
| Reactor Type | ASTeX 6500 series | N/A | Microwave Plasma-Enhanced CVD (MPCVD) |
| Growth Temperature | 730 | °C | Substrate temperature |
| Microwave Power | 4000 | W | CVD process parameter |
| Growth Pressure | 40 | Torr | CVD process parameter |
| Boron-to-Carbon (B/C) Ratio | 20,000 | ppm | High doping level for conductivity |
| Methane Concentration | 1 | % | CHâ/Hâ/TMB plasma gas mixture |
| Anodic Polarization Bias | +0.6 | V | Applied potential vs Ag/AgCl |
| Cathodic Polarization Bias | -0.6 | V | Applied potential vs Ag/AgCl |
| Maximum Absorbance Increase | 11-12 | % | Observed under -0.6 V bias (PEDOT:PSS + P6) |
| Peak Photocurrent Wavelength | 375 | nm | UV light illumination |
| Exposed Electrode Area | 1 | cm2 | Used for current density calculations |
Key Methodologies
Section titled âKey MethodologiesâThe BDD electrodes were fabricated using standard MPCVD techniques, followed by specialized surface preparation and biological immobilization.
- Substrate Preparation: Fused silica substrates (40 mm x 10 mm) were cleaned using an Oâ gas discharge plasma.
- Seeding: Substrates were drop-cast with an ultradispersed detonation nanodiamond colloidal suspension (7 nm size) followed by deionized water rinsing and spin-coating.
- MPCVD Growth: BDD films were grown in an ASTeX 6500 series reactor using a CHâ/Hâ/trimethylboron (TMB) plasma. Key parameters included 4000 W power, 40 Torr pressure, and a substrate temperature of 730 °C.
- Doping Control: A high B/C ratio of 20,000 ppm was maintained using TMB diluted in Hâ to achieve the necessary electronic conductivity for the current collector.
- Biophotoelectrode Assembly: Live L. indica trichomes were harvested and embedded in either 0.75% agar hydrogel or 0.5-1% conductive PEDOT/PSS polymer matrices.
- Electrochemical Testing: A three-electrode setup (BDD working electrode, Pt counter electrode, Ag/AgCl reference electrode) was used for chronoamperometry and spectroelectrochemical measurements under switched electric fields (+0.6 V and -0.6 V).
- Illumination: Monochromatic light was provided by mounted LEDs across the UV-visible spectrum (375 nm to 625 nm).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials required to replicate, scale, and optimize the BPEC systems described in this research. Our capabilities directly address the material specifications and customization needs of bioelectrochemistry engineers.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate the high-performance current collector used in this study, 6CCVD recommends:
- Heavy Boron-Doped PCD/BDD: The research explicitly requires high conductivity achieved through a B/C ratio of 20,000 ppm. 6CCVD offers Heavy Boron-Doped Polycrystalline Diamond (PCD/BDD) films with precisely controlled doping levels, ensuring the wide electrochemical window and low background current critical for BPEC stability and efficiency.
- Thin Film SCD/PCD: The 180 nm thickness is well within our standard range. We offer SCD (Single Crystal Diamond) and PCD (Polycrystalline Diamond) films from 0.1 ”m to 500 ”m thick, allowing researchers to explore the impact of film thickness on charge carrier diffusion and overall BPEC performance.
Customization Potential
Section titled âCustomization PotentialâThe success of this research relies on precise material dimensions and integration with other components (e.g., PEDOT:PSS). 6CCVD offers comprehensive customization services:
| Customization Requirement | 6CCVD Capability | Engineering Advantage |
|---|---|---|
| Custom Dimensions | Plates/wafers available up to 125 mm (PCD/BDD). | Allows for direct scale-up from the 40 mm x 10 mm lab samples to inch-size prototypes for commercial viability or large-scale space applications. |
| Substrate Integration | BDD films can be deposited on various substrates (e.g., Fused Silica, Silicon, Sapphire). | Ensures compatibility with existing experimental setups and allows for optimization of optical transparency and thermal management. |
| Integrated Metalization | In-house deposition of Au, Pt, Pd, Ti, W, and Cu contacts. | We can pre-metalize the BDD electrodes (e.g., with Pt contacts for counter electrodes or Ti/Au for stable ohmic contacts) to simplify assembly and enhance interface stability. |
| Surface Finish | Ultra-smooth polishing: Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD). | While the paper focused on thin films, highly polished surfaces are essential for uniform cell immobilization and minimizing surface defects that could interfere with bioelectronic charge transfer. |
Engineering Support
Section titled âEngineering SupportâThe observed polarization-dependent absorption and cathodic efficiency underscore the complexity of the bioelectronic interface. 6CCVDâs in-house PhD team provides expert consultation:
- Material Selection for Biophotovoltaics: We assist researchers in selecting the optimal BDD doping concentration and film morphology (SCD vs. PCD) to maximize charge extraction efficiency in similar Biophotoelectrochemical Cell (BPEC) projects.
- Interface Optimization: Our team offers technical guidance on surface termination (e.g., hydrogen or oxygen termination) and metalization strategies to ensure stable, long-term operation and robust connectivity between the diamond electrode and biological matrices like PEDOT:PSS.
- Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of sensitive diamond materials, supporting international research collaborations.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We present the change of light absorption of cyanobacteria in response to externally applied electrical polarization. Specifically, we studied the relation between electrical polarization and changes in light absorbance for a biophotoelectrode assembly comprising boron-doped diamond as semiconducting electrode and live <i>Limnospira indica</i>PCC 8005 trichomes embedded in either polysaccharide (agar) or conductive conjugated polymer (PEDOT-PSS) matrices. Our study involves the monitoring of cyanobacterial absorbance and the measurement of photocurrents at varying wavelengths of illumination for switched electric fields, i.e., using the bioelectrode either as an anode or as cathode. We observed changes in the absorbance characteristics, indicating a direct causal relationship between electrical polarization and absorbing properties of <i>L. indica</i>. Our finding opens up a potential avenue for optimization of the performance of biophotovoltaic devices through controlled polarization. Furthermore, our results provide fundamental insights into the wavelength-dependent behavior of a bio photovoltaic system using live cyanobacteria.