A 3D Printed Air-Tight Cell Adaptable for Far-Infrared Reflectance, Optical Photothermal Infrared Spectroscopy, and Raman Spectroscopy Measurements

At a Glance

Metadata	Details
Publication Date	2024-12-16
Journal	Instruments
Authors	A. Paolone, Arcangelo Celeste, Maria Di Pea, Sergio Brutti, Ferenc Borondics
Institutions	Synchrotron soleil, Sapienza University of Rome
Citations	1
Analysis	Full AI Review Included

Executive Summary

This analysis summarizes the development and validation of a versatile, 3D-printed air-tight cell designed for spectroscopic analysis of air and moisture-sensitive materials, particularly those used in electrochemical devices.

Core Value Proposition: The cell enables high-quality spectroscopic measurements (Optical Photothermal Infrared Spectroscopy (OPTIR), Raman, and Far-Infrared (Far-IR) Reflectance) in a quasi-normal reflectance geometry while preserving samples from atmospheric contamination outside a glove box.
Air-Tight Performance: Constructed from Polylactic acid (PLA) using 3D printing, the cell demonstrated effective sealing, maintaining an anhydrous environment for test samples (silica gel) for a minimum of 15 days.
Versatile Optical Access: The design accommodates interchangeable optical windows (CaF₂, ZnS, Diamond) to cover a broad spectral range, adapting the cell for different analytical techniques.
Cost-Effective Solution: Good quality OPTIR and Raman measurements were achieved using inexpensive CaF₂ windows (approx. EUR 7), significantly reducing operational costs compared to specialized cells.
Spectral Fidelity: Comparative measurements on materials like FeCO₃, crystalline Si, and Li₂CO₃ confirmed that the presence of the optical windows minimally affected spectral shape and features, proving the cell’s suitability for quantitative analysis.
Far-IR Capability: The cell was successfully adapted with a thin diamond window (EUR 480) to perform Far-IR reflectance measurements (100-700 cm^-1), crucial for analyzing lattice vibrations in compounds like Li₂CO₃.

Technical Specifications

The following table details the critical parameters and specifications of the 3D printed air-tight cell and its components.

Parameter	Value	Unit	Context
Cell Material	Polylactic acid (PLA)	N/A	3D Printed Structure
Fabrication Method	Fused Deposition Modeling (FDM)	N/A	Ultimaker 3+ Connect / Prusa i3 MK3
Air Tightness Duration	>15	days	Verified via silica gel test
O-Ring Cord Diameter	1.5	mm	Sealing mechanism
Minimum Objective Focal Length	9	mm	Constraint for optical systems
Maximum Sample Thickness	1	mm	Clearance below optical window
OPTIR Wavenumber Range	920 - 3100	cm^-1	Mid-IR absorption (QCL source)
Raman Wavenumber Range	50 - 3600	cm^-1	Visible laser excitation
Far-IR Reflectance Range	100 - 700	cm^-1	Requires Diamond window
CaF₂ Window (Raman/OPTIR)	12 / 1	mm	Diameter / Thickness (Cost: EUR 7)
ZnS Window (Raman/OPTIR)	12.7 / 0.5	mm	Diameter / Thickness (Cost: EUR 35)
Diamond Window (Far-IR)	10 / 0.4	mm	Diameter / Thickness (Cost: EUR 480)
CaF₂ Transmittance (1300 cm^-1)	95	%	Mid-IR transparency
CaF₂ Transmittance (900 cm^-1)	50	%	Limit due to phononic absorption
OPTIR Spectral Resolution	2	cm^-1	Acquired using 40× objective
Far-IR Spectral Resolution	4	cm^-1	Acquired using Si Bolometer

Key Methodologies

The development and validation of the air-tight spectroscopic cell followed a structured engineering and testing protocol:

Cell Design and Prototyping:
- The cell geometry was modeled using the OpenSCAD software, focusing on modularity and adaptability for various window sizes (10 mm, 12 mm, 12.7 mm, 25.4 mm).
- The critical design constraint was the 5.5 mm distance between the cover and the sample seat to ensure compatibility with short working distance objectives (9 mm focal length).
- The cell and cover were fabricated from PLA polymer using FDM 3D printing.
Sealing Mechanism Implementation:
- Air-tightness was achieved using a static tight configuration incorporating a 1.5 mm cord diameter O-ring, ensuring a seal between the optical window and the 3D printed body.
Air-Tightness Validation Test:
- Silica gel grains (deep blue when anhydrous) were sealed inside the cell prototypes (using CaF₂ windows).
- The color change of the silica gel (indicating hydration) was monitored over 15 days and compared against control samples exposed to ambient air to confirm long-term atmospheric protection.
Spectroscopic Performance Verification:
- OPTIR Testing: FeCO₃ powders were measured using a ZnS window. Spectra collected inside the cell were compared to those collected without the cell to verify minimal signal degradation and preservation of key vibrational modes (e.g., CO₃ asymmetric stretching mode at 1364 cm^-1).
- Raman Testing: Crystalline Si wafers were measured using both CaF₂ and ZnS windows. The resulting Raman spectra were compared to external measurements, confirming that window impurities did not interfere with the confocal measurement of the Si transversal optical phonon (520 cm^-1).
- Far-IR Reflectance Testing: Li₂CO₃ pellets were measured using the diamond window. The resulting reflectance spectrum (120-650 cm^-1) was fitted using the Drude-Lorentz model to confirm the accurate measurement of Li₂CO₃ lattice modes.

Commercial Applications

The 3D printed air-tight cell provides a critical tool for research and development in several high-tech sectors dealing with sensitive materials.

Energy Storage and Battery R&D:
- SEI Analysis: Crucial for investigating the Solid-Electrolyte Interphase (SEI) layer formation on Li-ion and post-Li-ion electrodes, which are highly sensitive to air and moisture.
- Post-Mortem Characterization: Enables detailed spectroscopic analysis of cycled or failed battery components (e.g., Li₂CO₃, LiCoPO₄) without altering their chemical state during transport or measurement.
Sensitive Material Science:
- Handling and analysis of hygroscopic, pyrophoric, or air-sensitive catalysts, metal powders, and organic compounds outside of specialized inert atmosphere chambers.
Analytical Chemistry and Microscopy:
- Custom Sample Holders: Provides a low-cost, rapidly customizable alternative to expensive commercial cells for specialized reflectance microscopy (OPTIR, Raman imaging) in research laboratories and synchrotron facilities.
- Infrared Spectroscopy: Facilitates high-quality Far-IR reflectance measurements, which are essential for studying low-frequency lattice vibrations in inorganic materials.
Pharmaceutical and Chemical Manufacturing:
- Quality control and characterization of moisture-sensitive active pharmaceutical ingredients (APIs) or precursors using non-contact OPTIR techniques.

View Original Abstract

Material characterization and investigation are the basis for improving the performance of electrochemical devices. However, many compounds with electrochemical applications are sensitive to atmospheric gases and moisture; therefore, even their characterization should be performed in a controlled atmosphere. In some cases, it is impossible to execute such investigations in a glove box, and, therefore, in the present work, an air-tight 3D printed cell was developed that preserves samples in a controlled atmosphere while allowing spectroscopic measurements in reflectance geometry. Equipped with a cheap 1 mm thick CaF2 optical window or a more expensive 0.5 mm thick ZnS window, the cell was used for both optical photothermal infrared and Raman spectroscopy measures; imaging of the samples was also possible. The far-infrared range reflectance measurements were performed with a cell equipped with a diamond window.

Tech Support

Original Source

DOI: https://doi.org/10.3390/instruments8040054

References

2020 - On the challenge of large energy storage by electrochemical devices [Crossref]
2024 - Comprehensive review of lithium-ion battery materials and development challenges [Crossref]
2024 - Polymeric composites in extrusion-based additive manufacturing: A systematic review [Crossref]
2021 - Dual detection of nafcillin using a molecularly imprinted polymer-based platform coupled to thermal and fluorescence read-out [Crossref]
2021 - A low cost microscope prototype [Crossref]
2016 - 3D printed double flow cell for local through-thickness anodization in aluminium [Crossref]