First-Principles Calculations for Glycine Adsorption Dynamics and Surface-Enhanced Raman Spectroscopy on Diamond Surfaces

At a Glance

Metadata	Details
Publication Date	2025-03-27
Journal	Nanomaterials
Authors	Shiyang Sun, Chi Zhang, Peilun An, Pingping Xu, Wenxing Zhang
Institutions	Inner Mongolia University of Science and Technology, Baogang Group (China)
Analysis	Full AI Review Included

Technical Documentation & Analysis: Diamond Substrates for Biointerfaces and SERS

Executive Summary

This analysis confirms the exceptional potential of MPCVD diamond (100) surfaces as highly stable and sensitive substrates for biodetection, specifically leveraging Surface-Enhanced Raman Spectroscopy (SERS).

Superior Stability: First-principles calculations (DFT) identified the Carboxyl-terminated (CAR) configuration of Glycine on the diamond (100) surface as the most stable, exhibiting the highest adsorption energy (5.03 eV).
Robust Biointerface: Ab initio Molecular Dynamics (AIMD) simulations confirmed the structural stability of the CAR configuration across a critical temperature range (300 K to 500 K), validating diamond’s robustness in biological environments.
Enhanced Detection: The diamond substrate demonstrated a remarkably evident SERS effect, significantly amplifying the Raman signals of adsorbed glycine molecules.
High Sensitivity: The highest SERS enhancement amplitude exceeded 200 times, with an average enhancement amplitude exceeding 50 times, particularly for characteristic carboxyl and amino group peaks.
Mechanism Confirmation: Enhancement is primarily attributed to charge transfer (COO- group) at the interface and molecular resonance (NH₂ groups), confirming the electronic suitability of the diamond surface for SERS applications.
Material Recommendation: The findings strongly support the use of high-quality, thin-film MPCVD Single Crystal Diamond (SCD) or Boron-Doped Diamond (BDD) for advanced biointerface and SERS probe development.

Technical Specifications

Parameter	Value	Unit	Context
Most Stable Adsorption Energy (E_ad)	5.03	eV	Carboxyl-terminated (CAR) configuration
Shortest Interfacial Distance (l_avg)	1.37	Å	CAR configuration
Highest SERS Enhancement Amplitude	> 200	times	Characteristic peaks (carboxyl/amino groups)
Average SERS Enhancement Amplitude	> 50	times	Overall glycine spectrum enhancement
AIMD Simulation Temperature Range	300 to 500	K	Simulating room, evaporative, and decomposition temperatures
Maximum Bond Length Fluctuation (Δd_max)	0.22	Å	Observed in CAR configuration
Final Stable RMSD (ATO Transformation)	0.8	Å	After dehydrogenation and phenyl-like ring formation
Energy Cutoff (DFT Calculation)	450	eV	VASP 6.4.1 implementation
Ion Energy Convergence Threshold	1 x 10^-5	eV	Required for stable structural configuration

Key Methodologies

The study relied on rigorous first-principles calculations and molecular dynamics simulations to analyze the glycine-diamond interface:

Computational Framework: Calculations were performed using the VASP 6.4.1 software package, employing the Generalized Gradient Approximation (GGA) with the PBE exchange-correlation function.
Slab Model Construction: A five-layer diamond slab model was used, with the bottom two layers fixed and H-terminated to mitigate surface polarity. A substantial vacuum layer (> 20 Å) was included to eliminate periodic boundary condition effects.
Surface Structure: The widely accepted (2 x 1) reconstructed diamond (100) surface was adopted, featuring dimers formed by adjacent surface carbon atoms.
Molecular Dynamics (AIMD): Ab initio molecular dynamics simulations were conducted using a Canonical NVT ensemble (constant temperature control) to study dynamic evolution and stability.
Temperature Parameters: Simulations were run at 300 K (room temperature), 400 K, and 500 K, with a total duration of 10 ps and a time interval of 1 fs per step.
Structural Quantification: Root Mean Square Deviation (RMSD) analysis was used to quantify the structural evolution and stability of the adsorbed glycine molecules under thermal stress.
SERS Calculation: Raman spectral information was derived from the Raman tensor, obtained via polarizability calculations of vibrational modes under the two-harmonic approximation.

6CCVD Solutions & Capabilities

The research demonstrates that diamond is an ideal substrate for high-sensitivity biodetection via SERS, requiring precise control over surface orientation, purity, and nanoscale structure. 6CCVD is uniquely positioned to supply the necessary high-specification MPCVD diamond materials to replicate and advance this research.

Applicable Materials for Bio-SERS Research

To achieve the high stability and strong SERS enhancement observed in this study, 6CCVD recommends the following materials:

Material Grade	Specification	Application Relevance
Optical Grade SCD (Single Crystal Diamond)	High purity, precise (100) orientation, Ra < 1 nm polishing.	Essential for replicating the specific (100) surface chemistry and achieving highly reproducible, low-noise SERS signals.
Boron-Doped Diamond (BDD)	Polycrystalline or Single Crystal, controlled Boron doping levels.	Highly recommended for maximizing SERS enhancement. Literature confirms BDD substrates significantly lower detection limits (e.g., 10^-4 M for MB molecules, per reference [17]).
Polycrystalline Diamond (PCD)	High-quality, inch-size wafers (up to 125 mm), Ra < 5 nm polishing.	Ideal for scaling up SERS biointerface arrays and large-area sensor development where cost-efficiency is critical.

Customization Potential for Advanced Biointerfaces

The successful implementation of diamond SERS probes requires precise material engineering, which is a core capability of 6CCVD:

Custom Dimensions and Thickness: The study highlights the importance of “thin-film diamond substrates.” 6CCVD offers SCD and PCD plates/wafers with thicknesses precisely controlled from 0.1 µm up to 500 µm, allowing researchers to optimize film thickness for specific SERS resonance effects. We offer wafers up to 125 mm in diameter (PCD).
Surface Orientation Control: We guarantee high-quality (100) oriented SCD substrates, critical for replicating the stable CAR adsorption configuration identified in this first-principles study.
Ultra-Smooth Polishing: For sensitive biointerfaces where molecular adsorption and SERS signal integrity are paramount, 6CCVD provides ultra-smooth polishing (Ra < 1 nm for SCD, Ra < 5 nm for inch-size PCD).
Integrated Metalization: Should the research transition to device fabrication or require plasmonic enhancement, 6CCVD offers in-house custom metalization services, including deposition of Au, Pt, Pd, Ti, W, and Cu layers.

Engineering Support

6CCVD’s in-house team of PhD material scientists specializes in optimizing MPCVD diamond properties for demanding applications. We provide expert consultation on:

Material Selection: Assisting researchers in choosing the optimal doping level (BDD) and crystal orientation (SCD (100)) for specific SERS biodetection projects.
Surface Functionalization: Advising on post-growth treatments necessary to achieve the desired surface termination (e.g., H-termination or O-termination) to control molecular adsorption stability and charge transfer mechanisms.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Based on first-principles calculations, the stability of three adsorption configurations of glycine on the (100) surface of diamonds was studied, leading to an investigation into the surface-enhanced Raman scattering (SERS) effect of the diamond substrate. The results showed that the carboxyl-terminated adsorption configuration (CAR) was the most stable and shortest interface distance compared to other configurations. This stability was primarily attributed to the formation of strong polar covalent bonds between the carboxyl O atoms and the surface C atoms of the (100) surface of diamonds. These results were further corroborated by first-principles molecular dynamics simulations. Within the temperature range of 300 to 500 K, the glycine molecules in the carboxyl-terminated adjacent-dimer phenyl-like (CAR) configuration exhibited only simple thermal vibrations with varying amplitudes. In contrast, the metastable ATO and carboxyl-terminated trans-dimer phenyl-like ring (CTR) configurations were observed to gradually transform into benzene-ring-like structures akin to the CAR configuration. After adsorption, the intensity of glycine’s characteristic peaks increased substantially, accompanied by a blue shift phenomenon. Notably, the characteristic peaks related to the carboxyl and amino groups exhibited the highest enhancement amplitude, exceeding 200 times, with an average enhancement amplitude exceeding 50 times. The diamond substrate, with its excellent adsorption properties and strong surface Raman spectroscopy characteristics, represents a highly promising candidate in the field of biomedicine.

Tech Support

Original Source

DOI: https://doi.org/10.3390/nano15070502

References

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