Supplementary information
Samaria /reduced graphene oxide nanocomposites; sonochemical synthesis and electrochemical evaluation
Amin Shiralizadeh Dezfuli,a Mohammad Reza Ganjali,*abHossein Jafaria, Farnoush Faridbodab
aCenter of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran, Iran.
b Biosensor Research Center, Endocrinology & Metabolism Molecular-Cellular Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran.
Corresponding Author
Prof. Mohammad Reza Ganjali
E-mail:
Fig. S1TEM image of SmG2
Electrochemical Determinations
DA, UA and AA normally coexist in the extracellular fluid of the central nervous system and blood serum. As discussed earlier they play critical roles in biological functions, so it is very important to selectively determine them with high sensitivity. In this study DPV method is used to determine individual AA, DA and UA at the SmG2 modified electrodes.
Fig. S2 shows the DPV responses at the SmG2 modified electrodes toward the AA, DA and UA. When the concentration of one specie is changing, concentrations of other species were kept constant. As illustrated in Fig. S2(a), the peak current increased linearly with increasing the concentration of AA in the range of 100–1800 μM in the 0.2 mM of DA and 0.1 mM UA. Fig. S2(b) exhibits the linear relationship between the peak current and concentration of AA is Ipa(μA)= 0.0038C (μM) + 0.0199 (R² = 0.9987).
The DA and UA currents and potentials remain constant with changing ascorbic acid’s concentration, indicating that their existence does not affect the determination of AA. Moreover increasing DA or UA does not affect neither others oxidation currents nor their oxidation potentials. This makes SmG2 a proper material for simultaneous determination of AA, UA and DA.
Fig.S2(c) demonstrates the DA oxidation peak currents relation with its concentrations in the presence of 1mM AA and 0.1mM UA. Linear dynamic range for DA is 10-400 μM described with the following equation: Ipa(μA) = 0.0198 C (μM) + 0.1096and thecorrelation coefficients of R2= 0.9979.
As it is shown in Fig.S2 (e) the UA oxidation peak current increased linearly with increasing the concentration of UA in the range of 0.5–500 μM. The linear relationship between the peak currents and concentrations of UA is Ipa (μA) = 0.0848 C(μM) + 0.9611(R² = 0.9975).
Fig.S2 a) DPVs at increasing concentrations of 100–1800 μM AA in the presence of 200 μM DA and 100 μM UA. c) increasing concentrations of 10-400 μM DA in the presence of 1 mM AA and 100 μM UA. e) increasing concentrations of 0.5-500 μM UA in the presence of 1 mM AA and 200 μM DA in 0.1 M PBS (pH 7.4). b,d and f) Linear relation between Currents and different concentrations of AA,DA and UA. Scan rates were 50 mV s−1 and pulse amplitudes were 25 mV.
The detection limits for AA, DA and UA is 5μM, 0.231μM and 0.012μM, respectively. Although as it is shown in Table S1, electrodes with lower detection limits are reported but in some cases the experiments conditions must be revised for example Phosphate buffer solution (PBS) was used for buffering pH around 4 or 5 or LOD and LOQ are the same or closer than 3σ/10σ in some experiments. Anyway wide dynamic range which cover biologically make SmG2 electrodes proper for clinically relevant ranges which are linked with most of diseases and biological functions of AA, DA and UA, Furthermore the as prepared sensors stability, reusability and reproducibility makes using them even more useful and feasible.
TableS1 Performances of different electrodes for simultaneous detection of DA and UA.
Electrode / Matrix / Technique / LDR(µM) / LOD (3σ) (µM) / Ref.DA / UA / DA / UA
SWCNTs/GCE / 0.1 M PBS pH 7.4 / DPV / 0.5–160 / 2–200 / 0.2 / 0.7 / [1]
3D Graphene / 0.1 M PBS pH 7.0 / DPV / _ / _ / 5 / 5 / [2]
Fe3O4/rGO/GCE / 0.1 M PBS pH 6.5 / DPV / 0.5-10 / _ / 0.12 / _ / [3]
AuNPs@MoS2 /GCE / 0.1 M PB pH 7.0 / DPV / 0.05–30 / 50–40000 / 0.05 / 10 / [4]
Au@Pd-RGO/GCE / 0.1 M PBS pH 7.0 / DPV / 0.01–100 / 0.02–500 / 0.002 / 0.005 / [5]
poly(SFO)/GCE / acetate buffer
(0.1 M, pH 4.0) / SW / 0.3–10 / 0.5–20 / 0.05 / 0.09 / [6]
P-4-ABA/GCE / 0.2 M PBS pH 4.5 / DPV / 5.0–100 / 0.001–10 / 0.0008 / 0.00085 / [7]
CPE/MWCNTs/IL/
PdNPs / 0.1 M PBS pH 5.0 / DPV / 0.1–151 / 0.5–225 / 0.03 / 0.15 / [8]
Au/DNA/Au/poly(SFR)/GCE / 0.1 M PBS pH: 5.0 / DPV / 0.008–1.1 / 0.09–12 / 0.0002 / 0.008 / [9]
Stability, Reproducibility and Reusability
Stability, reproducibility and reusability are the most important factors in making biosensors. Although many modifiers has been suggested for determination of DA, AA and UA but stability and reproducibility of results are still the main concerns. Besides green, facile and low cost synthesis methods can fulfil our goals. In this study for testing Electrode stability SmG2 nanoparticles were kept in the PBS for 4 months and electrochemical Analysis was performed monthly. The results shows that the electrode performance is fairly solid and the oxidation peak currents decayed only about 8.6%, 7.8% and 9.4% respectively for AA, DA and UA. This considerable stability is attributed to Samaria nanoparticles stability which preserve the electrode morphology and performance for long term. Moreover, the reproducibility was checked by measuring the electrochemical response of the SmG2 working electrode for six different electrodes in a solution containing 0.1 mM DA, 0.1 mM UA and200 μM of AA. The relative standard deviation (RSD) of peak currents was 2.89%, 3.05% and 3.71%, demonstrating acceptable reproducibility of the SmG2 modified electrodes. For investigating reusability, the measurements were performed on modified electrodes then after just PBS solution rinsing on the tip of electrodes another measurements was conducted. The experimental data showed that the electrochemical signal from the SmG2 working electrode toward the DA after sample solution rinsing could still maintain 96% of the original signal. The analytical performance of the proposed electrode is compared with some recent references in Table S1. As discussed in pervious section, although there was no obvious magnificent difference in the analytical performance between them, SmG2 modified electrodes show considerable LDR and proper DL which covers biologically functional AA,DA and UA concentration range. Besides their Facile, green, cheap synthesis methods, there are three major advantages in using SmG2 for modifying GC Electrodes; its considerable stability, reproducibility and reusability makes it very good candidate for simultaneous determination of AA, DA and UA.
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