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Supporting Information

Photo-electrochemical properties of CuO–TiO2 heterojunctions for glucose

sensing

David Maria Tobaldi,a* Claudia Espro,b Salvatore Gianluca Leonardi,b L Lajaunie,c,d Maria Paula Seabra,a JJ Calvino,c,d Silvia Marini,b João António Labrincha,a Giovanni Nerib*

a Department of Materials and Ceramics Engineering and CICECO−Aveiro Institute of Materials – University of Aveiro, 3810–193 Campus Universitário de Santiago, Portugal

b Department of Engineering, University of Messina, C.da Di Dio, I–98166 Messina, Italyc Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias,

Universidad de Cádiz, Campus Río San Pedro S/N, Puerto Real 11510, Cádiz, Spain

d Instituto Universitario de Investigación de Microscopía Electrónica y Materiales (IMEYMAT), Facultad de Ciencias, Universidad de Cádiz, Campus Río San Pedro S/N, Puerto Real 11510, Cádiz, Spain

KEYWORDS: Non-enzymatic electrochemical sensors; Photochemical activation; glucose; CuxO–TiO2 junction

*Corresponding authors

E-mail addresses: david.tobaldi@ua.pt; david@davidtobaldi.org (DM Tobaldi); gneri@unime.it (G Neri).

Twitter: @D14MT (DM Tobaldi)

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry C.This journal is © The Royal Society of Chemistry 2020

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Figure S1. SEM images of a Ti1.00:Cu0.10 (a,b), and corresponding EDX maps (c,d).

Figure S2. SEM image of: a) pure TiO2 sample; b) Cu-TiO2 sample.

b ba

c d

a b

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Figure S3. STEM-BF micrograph of Ti1.00:Cu0.25.

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Figure S4. STEM EDS analyses of Ti1.00:Cu0.25 a) EDS individual chemical map of Ti; b) EDS individual chemical map of Cu.

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Figure S5. SR-EELS analysis of Ti1.00:Cu0.25. a) Cu-L2,3 edge integrated intensity EELS map. The red square highlights the area used to extract the corresponding EELS spectrum; b) EELS spectrum showing the Cu-L2,3 fine structures.

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Figure S6. STEM analyses of Ti1.00:Cu0.50. a) STEM-HAADF micrograph. The red arrows highlight the presence of bigger Cu-based NPs with a size of about 10 nm; b) STEM-HAADF micrograph of another area of the specimen showing small Cu-based NPs with a size below 2nm; c) STEM-HAADF micrograph. The red square highlights the area used for the EDS analysis; d) Corresponding EDS chemical maps.

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15 20 25 30 35 40 45 50 55 60 65 70 75 80 85

0

1x103

2x103

3x103

4x103

5x103

6x103

2 (°)

Inte

nsity

(cou

nts)

Figure S7. Graphical output of the Rietveld QPA refinement, specimen: Ti1.00:Cu0.75. The red continuous line represents the calculated pattern, the black open circles represent the observed pattern, and the difference curve between observed and calculated profiles is plotted below. The position of reflections is indicated by the small vertical bars (black: anatase; green: tenorite).

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20 30 40 50 60 70 80 90 100

2 (°)

Inte

nsity

(arb

. un.

)

30 32 34 36 38 40 42 44

Inte

nsity

(arb

. un.

)

2 (°)

Figure S8. Graphical output of the WPPM modelling, specimen Ti1.00:Cu1.00. The red line represents the calculated pattern and the black open circles the measured one. The dark grey (upper) and blue (lower) continuous lines at the bottom are the difference curves between observed and calculated profiles, for the proposed bimodal and unimodal size distribution models, respectively. A magnification in the 30-44 °2θ range is shown in the inset, in order to highlight the difference in the most intense reflections of tenorite – (111) and ( ), at 38.79 and 35.59 °2θ, respectively.1̅11

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Table S1 – WPPM agreement factors and average domain diameter of the two fractions of tenorite according to the proposed bimodal size distribution model.

Agreement factors Mean crystalline domain diameter (nm)SampleRwp (%) Rexp (%) 2 ⟨Dtnr_0⟩ ⟨Dtnr_1⟩

50D 1.72 1.86 0.93 15.9±1.0 2.0±1.354B 1.48 1.22 1.21 34.1±1.0 2.8±1.254C 1.75 1.14 1.53 36.8±5.1 1.3±0.754D 1.79 1.05 1.71 47.8±5.4 1.7±0.5

0.1 1 10 1000.0

0.1

0.2

0.3

0.4

0.5

0.6

Domain diameter (nm)

Freq

uenc

y (ar

b. un

.)

1 10 1000.00

0.05

0.10

0.15

Domain diameter (nm)

Freq

uenc

y (ar

b. un

.)

0.01 0.1 1 10 1000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Domain diameter (nm)

Freq

uenc

y (ar

b. un

.)

0.01 0.1 1 10 1000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Domain diameter (nm)

Freq

uenc

y (ar

b. u

n.)

Figure S9. Bimodal size distribution for tenorite in: a) Ti1.00:Cu1.00; b) Ti0.75:Cu1.00; c) Ti0.50:Cu1.00; d) Ti0.25:Cu1.00. Size is reported in log-scale in all of the figures.

a) b)

c) d)

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200 300 400 500 600 700 800 9000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0 TiO2

Ti1.00:Cu0.10 Ti1.00:Cu0.25 Ti1.00:Cu0.50 Ti1.00:Cu0.75 Ti1.00:Cu1.00 CuO

Wavelength (nm)Abso

rban

ce (K

ubel

ka-M

unk

units

)

Figure S10. DR spectra for selected specimens.