TITLE: Nanomaterials UV-Vis measurement
AUTHORS: Ana Carrazco Quevedo, Emily J. Guggenheim, Sophie M. Briffa, Anastasios Papadiamantis

[DESCRIPTION]
<div class = "text-blocks"><div class = "text-block">This SOP describes a sample preparation procedure for particle size  measurements in gold NP suspensions. The procedure involves  quantification of the extinction of light that is measured from the  spectral pattern using absorbance. UV-Vis refers to the ultraviolet to  visible spectral region of light, the absorption of which is size  dependent at the nanoscale. UV-Vis is therefore an ideal technique for  the size characterisation of NP suspensions through absorbance at an  appropriate wavelength.  The settings defined below will be refined to optimise results during  the subsequent runs.</div></div>

[STEPS]
?. Sample PreparationVortex each AuNP stock suspension for 2 minutes.Dilute the Au suspensions 1:2. Pipette 0.5 mL of the Au stock  suspension and 0.5 mL UPW 18.2 MΩcm to obtain a final volume of 1 mL and  a mass concentration of 25 mg/L.
?. Sample AnalysisSwitch the UV-Vis Spectrometer (Jenway  6800 Double Beam Spectrometer Figure 3) on and leave for 20 minutes to  allow the lamp to heat up.Use 18.2 MΩcm UPW as the reference sample.Before  starting the measurements, the parameter settings shown in Table 1  should be set in the software (Flight Deck 1.0 or higher).   AB1Parameter&nbsp;Settings2Measurement ModeSpectrum Scan3Data ModeABS4Start Wavelength680 nm5End Wavelength380 nm6Scan Speed400 nm/min7Sampling Interval0.58Slit Width1.59Path Length10Table 1. UV-Vis Parameter settings4. Baseline correction should be obtained by running a baseline using  two cuvettes filled with 1 mL of UPW each, placed in the sample holders  (Figure 4).5. The reference cuvette with 1 mL UPW should then be left untouched  and the other cuvette should be replaced with a new cuvette containing 1  mL of one of the diluted AuNP suspensions. A new cuvette should be used  for each different sample analysed.6. Three spectrum scan runs  for each known BBI AuNP diluted suspension (5, 20, 40, 60 and 100 nm)  should be obtained. Therefore a total of 15 scans should be collected.  The results obtained should be reported as explained in Section 6 below  and a calibration curve should be plotted.7. Following this  three spectrum scan runs for the unknown monodispersed AuNP suspension  containing a monodispersed suspension of NPs of an unknown size.
AB1Parameter&nbsp;Settings2Measurement ModeSpectrum Scan3Data ModeABS4Start Wavelength680 nm5End Wavelength380 nm6Scan Speed400 nm/min7Sampling Interval0.58Slit Width1.59Path Length10
?. Reporting results1. Note the average maximum absorption wavelength (λmax) of each if the UV-Vis readings (n=15) in the results Table 1.2. Note the maximum absorption (AUmax) of each of the UV-Vis readings (n=15) in the results Table 2.3. To add the results click the pencil button on the right hand-side of the results table.4. The average λ, AU and and standard deviations for each set of measurements will be automatically calculated.5. Plot the spectra of absorbance vs wavelength (nm) for each measurement (n=15).6. Save the plots as a .jpg image and upload it using the File button above the results tables.
?. Data upload1. Extract the raw experimental data for each measurement (n=18) as a .CSV or excel compatible file.2. Upload the files using the File button above the results table.3. The raw data will be used to calculate the Energy Band Gap (EBG) for  each nanomaterials sample using Tauc plots and shared with partners.4. (Optional) Add any comments you like in the comments section at the bottom of the results page.