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Lab Handout — Hydrothermal ZnO & 3 mol% Ni–ZnO Project

Lab Handout: Hydrothermal Synthesis of ZnO & 3 mol% Ni–ZnO (1-Month Nano Project)

Strict SOP UV–Vis + FTIR + Conductivity + Photoresponse
Supervisor: Dr. Sibi K. S.  |  Project Duration: 4 weeks  |  Samples: ZnO (undoped) and Ni–ZnO (3 mol% Ni)
Tip: Use browser Print → Save as PDF for a clean printable handout.

1) Safety Instructions (Mandatory)

  1. Wear lab coat, gloves, and safety goggles throughout.
  2. NaOH/KOH is corrosive — handle carefully; rinse spills immediately with water.
  3. Do not fill the Teflon autoclave above 80% capacity.
  4. Allow autoclave to cool naturally. Do not force open while hot/pressurized.
  5. Collect washings in proper waste container; do not pour into sink unless instructed.

2) Materials Required

Chemicals

  • Zinc acetate dihydrate Zn(CH3COO)2·2H2O (preferred) or ZnCl2
  • Nickel nitrate hexahydrate Ni(NO3)2·6H2O (for doped sample)
  • NaOH pellets/flakes (or KOH pellets)
  • PEG (recommended) / PVP / PVA (any one as capping agent)
  • DI water, acetone
  • Silver paste (for electrodes)

Instruments

  • Hydrothermal autoclave (Teflon-lined)
  • UV–Vis spectrophotometer
  • FTIR spectrometer
  • Solar simulator
  • Two-probe conductivity setup

3) Exact Chemical Quantities (100 mL batches)

A) Undoped ZnO (0.10 M Zn2+) — 100 mL

ChemicalAmountNotes
Zinc acetate dihydrate 2.20 g Dissolve in ~70 mL DI, make up to 100 mL total volume
PEG (optional, recommended) 0.50 g Add after zinc salt dissolves
1.0 M NaOH As required Add dropwise to reach pH 10–11

B) 3 mol% Ni–ZnO — 100 mL

ChemicalAmountNotes
Zinc acetate dihydrate 2.20 g Same as undoped
Nickel nitrate hexahydrate 0.087 g (87 mg) 3 mol% Ni relative to Zn
PEG (recommended) 0.50 g Add after salts dissolve
1.0 M NaOH As required Add dropwise to reach pH 10–11

Prepare 1.0 M NaOH (100 mL stock)

  1. Weigh 4.0 g NaOH pellets.
  2. Dissolve in ~70 mL DI water (stir; solution heats up).
  3. Make total volume to 100 mL.
  4. Label: “NaOH 1.0 M, date, preparer”.

4) Hydrothermal Synthesis Procedure (Strict SOP)

Step 1 — Prepare metal salt solution

  1. Take a clean 250 mL beaker; add ~70 mL DI water.
  2. Dissolve zinc acetate dihydrate (2.20 g).
  3. For Ni–ZnO only: add Ni(NO3)2·6H2O (87 mg).
  4. Stir for 15 minutes until clear solution forms.
  5. Add PEG (0.50 g), stir 10 minutes.

Step 2 — Adjust pH to 10–11

  1. Measure pH using pH paper.
  2. Add 1.0 M NaOH dropwise with continuous stirring.
  3. Stop at pH 10–11 (do not exceed pH 11.5).
  4. Record final pH in notebook.

Step 3 — Hydrothermal treatment

  1. Transfer mixture to Teflon liner (max 80% filled).
  2. Seal autoclave properly.
  3. Heat at 160 °C for 8 hours.
  4. Cool naturally to room temperature before opening.

Step 4 — Washing and drying

  1. Filter precipitate using filter paper.
  2. Wash with DI water 3×.
  3. Final wash with acetone 1× (optional but recommended).
  4. Dry at 70–80 °C for 3 hours (or overnight air-dry).
  5. Label samples: ZnO, Ni–ZnO (3%).
Optional annealing (if furnace available): Heat powders at 300 °C for 2 hours, cool naturally, store airtight.

5) Characterization & Data Analysis (Do exactly in this order)

A) UV–Vis (Band gap)

  1. Disperse 2 mg powder in 3 mL DI water (or ethanol).
  2. Shake/sonicate for 10 min.
  3. Scan 300–800 nm; save CSV.
Convert wavelength to photon energy:
hν (eV) = 1240 / λ (nm)
Tauc (direct bandgap):
(A·hν)2 vs hν → extrapolate linear part to x-axis gives Eg

B) FTIR

  1. Run FTIR in range 400–4000 cm⁻¹.
  2. Record peak positions.
  3. Note Zn–O region (< 600 cm⁻¹) and OH bands (~3400 cm⁻¹).

C) Pellet making (for conductivity)

  1. Take ~0.3 g powder and press into pellet.
  2. Measure pellet diameter and thickness.
  3. Apply silver paste on both flat faces; dry 10–15 min.

D) Two-probe conductivity

  1. Record I–V from −5 V to +5 V.
  2. Compute slope to get resistance R.
  3. Calculate resistivity and conductivity using pellet dimensions.
R = ΔV / ΔI
ρ = R · (A / L)
σ = 1 / ρ
A = cross-sectional area (cm²), L = thickness (cm)

E) Photoconductivity (Solar simulator)

  1. Apply constant bias: 5 V.
  2. Record current vs time:
    • Dark: 60 s
    • Light ON: 60 s
    • Light OFF: 60 s
    • Repeat 3 cycles
  3. Compute photosensitivity.
S = (I_light − I_dark) / I_dark

6) Weekly Timeline (Strict)

WeekTasksOutput to Submit
Week 1 Synthesize ZnO and Ni–ZnO (3%), wash, dry, label, repeat one batch if time permits. Lab notes (pH, temp, time), photos of powders, sample labels
Week 2 UV–Vis scans, Tauc plots; FTIR spectra. UV–Vis CSV + Tauc plots + FTIR plots
Week 3 Pellet preparation, I–V curves, conductivity calculation. I–V graphs + conductivity table
Week 4 Solar simulator ON/OFF photoresponse; finalize graphs; draft report. Current–time plots + sensitivity values + draft report

7) Data Submission Checklist (Do not skip)

  • Raw UV–Vis data (CSV) for both samples
  • Tauc plots with Eg values marked
  • FTIR spectra with peak positions table
  • Pellet diameter & thickness measurements
  • I–V plots and resistance extraction method
  • Resistivity (ρ) and conductivity (σ) table
  • Photoresponse (I–t) plots with ON/OFF cycles
  • Photosensitivity values (S)
  • Complete lab notebook (pH, temperature, time logs)
Notes: Label every container; do not mix glassware between samples; repeat at least one measurement for reliability.
Document version: v1.0

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