Determination of Caffeine in Energy Drinks Using a Composite Modified Sensor Based on Magnetic Nanoparticles

At a Glance

Metadata	Details
Publication Date	2025-05-20
Journal	Molecules
Authors	Katarzyna Tyszczuk‐Rotko, Aleksandra Liwak, Aleksy Keller
Institutions	Maria Curie-Skłodowska University
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Sensitivity Caffeine Sensing via Modified BDD

Executive Summary

This document analyzes the development of a highly sensitive voltammetric sensor (BDDE/Nafion@Fe₃O₄/BiF) for the determination of caffeine (CAF) in energy drinks. The core material, a Boron-Doped Diamond Electrode (BDDE), is critical to the sensor’s performance.

Core Achievement: Fabrication of a composite-modified BDDE sensor achieving ultra-low detection limits for caffeine using Differential-Pulse Adsorptive Stripping Voltammetry (DPAdSV).
Material Foundation: The sensor relies on a highly conductive, polished Boron-Doped Diamond (BDD) substrate, modified with a Nafion/Fe₃O₄ nanocomposite and an in situ deposited Bismuth Film (BiF).
Performance Metrics: Achieved a Limit of Detection (LOD) of 0.043 nM and a wide linear range spanning four orders of magnitude (0.5 to 10,000 nM).
Mechanism Enhancement: The Nafion/Fe₃O₄/BiF modification significantly improves electron transfer kinetics (lowest xº value of 2.10) and increases the number of active adsorption sites for CAF.
Selectivity: The sensor demonstrated high selectivity, tolerating a 100-fold excess of common energy drink excipients (glucose, vitamins, citric acid) with signal changes of less than ±10%.
6CCVD Value Proposition: 6CCVD specializes in the custom fabrication of high-quality BDD substrates, offering precise control over doping levels (e.g., 1000 ppm) and dimensions required for replicating or scaling this advanced electrochemical sensing technology.

Technical Specifications

The following hard data points were extracted from the optimized DPAdSV procedure and material characterization:

Parameter	Value	Unit	Context
Limit of Detection (LOD)	0.043	nM	BDDE/Nafion@Fe₃O₄/BiF sensor
Limit of Quantification (LOQ)	0.14	nM	BDDE/Nafion@Fe₃O₄/BiF sensor
Linear Range	0.5 - 10,000	nM	Caffeine concentration range
BDD Doping Level	1000	ppm	Boron concentration in the diamond film
BDD Resistivity	0.075	Ωm	Electrical property of the BDD substrate
BDD Inner Diameter	3	mm	Geometric size of the working electrode
Deposition Potential ($E_{dep}$)	-0.95	V	Potential for simultaneous BiF deposition and CAF accumulation
Deposition Time ($t_{dep}$)	60	s	Optimized time for BiF/CAF accumulation
DPAdSV Amplitude ($\Delta E_{A}$)	150	mV	Optimized voltammetric parameter
Scan Rate ($v$)	100	mV/s	Optimized voltammetric parameter
Modulation Time ($t_{m}$)	6	ms	Optimized voltammetric parameter
Supporting Electrolyte	0.4	M H₂SO₄	Optimized concentration for highest CAF signal
Bi(III) Concentration	5	µM	Concentration in the supporting electrolyte
Fe₃O₄ Mass	0.5	mg	Mass used in 100 µL of 3% Nafion nanocomposite
Electrode Reproducibility (RSD)	5.9	%	Electrode-to-electrode reproducibility (n=15)

Key Methodologies

The BDDE/Nafion@Fe₃O₄/BiF sensor fabrication and analysis procedure involved precise material preparation and electrochemical optimization:

BDDE Preparation: The commercial BDD electrode (3 mm diameter, 1000 ppm B-doped) was polished using 0.3 µm alumina slurry to ensure a clean, smooth surface.
Nanocomposite Synthesis: A nanocomposite containing 0.5 mg of Fe₃O₄ nanoparticles in 100 µL of 3% (v/v) Nafion (in ethanol) was prepared and sonicated for 2 hours.
Surface Modification: 0.5 µL of the nanocomposite was applied to the polished BDDE surface and dried for 5 minutes at room temperature.
Electrolyte Selection: The base electrolyte was optimized to 0.4 M H₂SO₄, leveraging the low pH to protonate CAF for enhanced adsorption in the cation-exchange Nafion layer.
In Situ BiF Deposition & CAF Accumulation: The modified electrode was placed in the electrolyte containing 5 µM Bi(III) and CAF. Bismuth film deposition and CAF accumulation were performed simultaneously for 60 s at an optimized potential of -0.95 V.
Voltammetric Measurement: Differential-Pulse Adsorptive Stripping Voltammograms (DPAdSVs) were registered from 0.25 to 1.85 V using optimized parameters ($\Delta E_{A}$ = 150 mV, $v$ = 100 mV/s, $t_{m}$ = 6 ms).

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the foundational diamond materials and advanced processing required to replicate, scale, and enhance this high-performance electrochemical sensing platform.

Applicable Materials

The success of this sensor is fundamentally dependent on the quality and precise doping of the BDD substrate. 6CCVD offers the following materials tailored for this application:

Boron-Doped Diamond (BDD) Wafers/Plates: We provide MPCVD BDD films with highly controlled boron doping levels.
- Required Specification: We can precisely match the 1000 ppm doping level and 0.075 Ωm resistivity cited in the research, ensuring high conductivity and optimal electrochemical activity.
- Custom Dimensions: While the paper used a 3 mm diameter electrode, 6CCVD can supply BDD plates up to 125 mm in diameter, enabling the fabrication of high-density sensor arrays or larger electrodes for industrial scale-up.
Polycrystalline Diamond (PCD) Substrates: Available in thicknesses from 0.1 µm to 500 µm, providing robust, high-surface-area platforms suitable for nanocomposite modification.

Customization Potential

To move beyond the laboratory setup and into commercial or advanced research applications, 6CCVD offers critical customization services:

Service	Relevance to Research Paper	6CCVD Capability
Precision Polishing	The paper required polishing with 0.3 µm alumina slurry.	6CCVD offers superior, standard polishing down to Ra < 5 nm (for inch-size PCD) or Ra < 1 nm (for SCD), ensuring the ideal surface morphology for uniform nanocomposite application and enhanced repeatability.
Custom Dimensions	The paper used a small 3 mm electrode.	We provide custom laser cutting and shaping services to produce specific electrode geometries (e.g., discs, squares, or complex patterns) on wafers up to 125 mm.
Integrated Metalization	The paper used in situ deposited Bismuth Film (BiF).	6CCVD offers internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu). For next-generation sensors, we can deposit noble metal films (e.g., Pt or Pd) directly onto the BDD surface to act as stable, pre-integrated catalytic sites, potentially replacing or stabilizing the in situ BiF.
Thickness Control	BDD film thickness is crucial for mechanical stability and performance.	We offer precise thickness control for BDD films from 0.1 µm up to 500 µm, mounted on various substrates (e.g., Si, W, or free-standing).

Engineering Support

The successful optimization of the BDDE/Nafion@Fe₃O₄/BiF sensor required extensive parameter tuning (pH, $E_{dep}$, $t_{dep}$, $\Delta E_{A}$). 6CCVD’s in-house PhD team specializes in the fundamental material science of MPCVD diamond and can assist researchers and engineers with:

Material Selection: Guiding the choice of optimal BDD doping levels and surface termination (e.g., H-terminated vs. O-terminated) for specific electrochemical applications, such as high-sensitivity voltammetric sensing.
Interface Optimization: Consulting on surface preparation techniques to maximize adhesion and performance of subsequent modification layers (like Nafion and magnetic nanoparticles).
Scaling and Integration: Providing technical support for transitioning from small, single-electrode setups (3 mm) to larger, integrated sensor arrays on full wafers.

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

View Original Abstract

A new voltammetric sensor (BDDE/Nafion@Fe3O4/BiF) was fabricated by applying a nanocomposite drop of Fe3O4 magnetic nanoparticles in Nafion onto the polished boron-doped diamond electrode (BDDE) surface. Then, after drying (5 min at room temperature), the electrode was electrochemically modified with bismuth film (BiF) during in situ analysis. The Nafion@Fe3O4/BiF modification of the BDDE contributes to the acquisition of the highest differential-pulse adsorptive stripping voltammetric (DPAdSV) signals of caffeine (CAF) due to the improvement of electron transfer and the increase in the number of active sites on which CAF can be adsorbed. The DPAdSV signals exhibited a linearly varied oxidation peak with the CAF concentration range between 0.5 and 10,000 nM, leading to the 0.043 and 0.14 nM detection and quantification limits, respectively. The practical applicability of the DPAdSV procedure using the BDDE/Nafion@Fe3O4/BiF was positively confirmed with commercially available energy drinks.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules30102219

References

2016 - Bismuth particles Nafion covered boron-doped diamond electrode for simultaneous and individual voltammetric assays of paracetamol and caffeine [Crossref]
2016 - Simultaneous determination of caffeine and paracetamol by square wave voltammetry at poly(4-amino-3-hydroxynaphthalene sulfonic acid)- modified glassy carbon electrode [Crossref]
2019 - Adsorptive stripping voltammetric method for the determination of caffeine at an integrated three-electrode screen-printed sensor with carbon/carbon nanofibers working electrode [Crossref]
2010 - Simultaneous voltammetric determination of acetaminophen, aspirin and caffeine using an in situ surfactant-modified multiwalled carbon nanotube paste electrode [Crossref]
2019 - Simultaneous Determination of Caffeine and Pyridoxine in Energy Drinks using Differential Pulse Voltammetry at Glassy Carbon Electrode Modified with Nafion® [Crossref]
2012 - A Carbon Nanotube Modified Electrode for Determination of Caffeine by Differential Pulse Voltammetry [Crossref]
2017 - Green Electrochemical Sensor for Caffeine Determination in Environmental Water Samples: The Bismuth Film Screen-Printed Carbon Electrode [Crossref]
2011 - Health Effects of Energy Drinks on Children, Adolescents, and Young Adults [Crossref]
2014 - Insufficient Sleep in Adolescents and Young Adults: An Update on Causes and Consequences [Crossref]
2009 - Caffeinated energy drinks—A growing problem [Crossref]