Polypropylene Modified with Ag-Based Semiconductors as a Potential Material against SARS-CoV-2 and Other Pathogens

S1 Polypropylene modified with Ag-based semiconductors as potential material against SARS-CoV-2 and other pathogens Marcelo Assisa*, Lara K. Ribeiroa,b , Mariana O. Gonçalvesc, Lucas H. Staffad,e , Robert S. Paivad, Lais R. Limad, Dyovani Coelhob, Lauana F. Almeidaf,g , Leonardo N. Moraesf,g , Ieda L. V. Rosab, Lucia H. Mascarob, Rejane M. T. Grottof,g , Cristina P. Sousac, Juan Andrésa, Elson Longob, Sandra A. Cruzd aDepartment of Physical and Analytical Chemistry, University Jaume I (UJI), Castelló 12071. bCDMF, LIEC, Federal University of São Carlos - (UFSCar), São Carlos, SP, 13565-905 Brazil. cBiomolecules and Microbiology Laboratory (LaMiB), Biotechnology Graduation Program (PPGBiotec), Federal University of São Carlos (UFSCar), São Carlos, SP, 13565-905, Brazil. dChemistry Department, Federal University of São Carlos (UFSCar), São Carlos, SP, 13565-905, Brazil. eDepartment of Materials Engineering, Federal University of São Carlos - (UFSCar), São Carlos, SP, 13565-905 Brazil. fSchool of Agriculture, São Paulo State University (Unesp), Botucatu, SP, 18610-034, Brazil. gMolecular Laboratory of Clinical Hospital of Botucatu, Medical School, São Paulo State University (Unesp), Botucatu, SP, 18618-687, Brazil. S2 *Corresponding author: [email protected] SUPPORTING INFORMATION Synthesis of Ag-based Semiconductors Silver Tungstate (α-Ag2WO4), Silver Molybdite (β-Ag2MoO4) and Silver Chromite (Ag2CrO4) were synthesized by the coprecipitation (CP) method (CP) in an aqueous medium at room temperature. Two solutions were made, adding 1x10-3 mol of the lattice former salt (Na2WO4.2H2O (Sigma-Aldrich, 99.8%), Na2MoO4.2H2O (AlfaAesar, 99%) and K2CrO4 (Alfa-Aesar, 99.9%)) to 50.0 ml of distilled water and 2x10-3 mol of AgNO3 (Cenabras, 99.8%) to 50.0 ml of distilled water. Both solutions were kept at 70°C under constant stirring. The AgNO3 solution was added to lattice former salt solution, then a precipitate appeared. The precipitate obtained was washed several times with distilled water and dried in an oven at 60 ° C for 12h. Characterizations of Semiconductors/PP Composite Materials These composite materials were characterized by using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), absorption spectroscopy in the regions of Ultraviolet and Visible (UV-Vis) and contact angle. To XRD analysis a Rigaku X-ray diffractometer, model DMax2500PC. The equipment will be operated in the conditions of 40 kV and 150 mA, the radiation used for the measurements will be that of Cu-Kα (λ = 1.5406 Å). A scan rate of 2°/min were used in the range of 10° to 80°. Raman spectroscopy was carried out using an iHR550 spectrometer (Horiba Jobin-Yvon, Japan) with a charge-coupled device (CCD) detector and an argon-ion laser (MellesGriot, USA) operating at 633 nm with a power of 200 mW. The diffractograms were compared with the diffraction patterns according to the JCPDS (Joint Committee on Powder Diffraction Standards) and ICSD (Inorganic Crystal Structure Database) crystallographic sheets. FTIR was performed using a Jasco FT/IR-6200 (Japan) spectrophotometer operated in S3 absorbance mode at room temperature in the range of 470-4000 cm-1. After, analysis by UV-Vis were performed on a Cary equipment, model 5G by the method of total diffuse reflectance using an integrating sphere. Shortly thereafter, the composites were characterized by the AFM images. The characterization was obtained using a Flex-AFM controlled by Easyscan 2 software (Nanosurf, Switzerland) in Constrast Phase mode on active vibration isolation table (model TS-150, Table Stable LTD®). The cantilever used for image acquisition was silicon Tap190G (Resonant frequency 190 kHz, force constant 48 N/m, Budget Sensors) in setpoint of 50%. To finalize the structural surface characterizations, contact angle analyses were carried out using the method of sessile drop in static mode in a goniometer (Model 260 F4 Series Ramé-hart). On the surface of each sample, a 5µL drop of distilled water was deposited, and the angle formed between the drop and the polymer surface was determined by DROPimage Advanced software. The analyses were performed in triplicate and data were treated using harmonic media. The rheological behavior of composites, as well as the degree of dispersion and the interaction between PP and semiconductor oxides, were evaluated by measures of complex viscosity (*) as a function of frequency (). in a parallel plate rheometer (Anton Paar MCR 305), The measurements were carried out at 190 °C, in oscillatory mode, using a 25 mm diameter plates, 1 mm gap and a frequency range of 0.1 to 500 rad/s. The deformation used was 1%, as it is in the linear viscoelastic range, defined according to a previous amplitude sweep test. Stress-strain curves were obtained in the EMIC DL3000 equipment with a load cell of 20N and a strain rate of 2.5×10−4 mm/min. The test was based on ASTM D 638: 2014 and rectangular samples, in film form, with approximate dimensions of 30x5 mm and approximate thickness of 0.13 mm were used. Differential scanning calorimetry (DSC) was performed in a DSC 203 F3-Maia (Netzsch) on samples of 5–10 mg under the following thermal programming: heating from -70°C to 200°C at a rate of 10°C/min. The degree of crystallinity of PP was calculated from melting enthalpy (ΔHm), using Equation 1, where φ is the mass fraction of the Ag-based semiconductor (0, 0.5, 1, or 3 wt%) and is the melting enthalpy for hypothetically 100% crystalline PP, equal 𝛥𝐻 0 𝑚 to 207 J/g. (Eq. 1) % 𝐶 = 𝛥 𝐻 𝑚 (100 ― 𝜑 ) 𝛥𝐻 0 𝑚 𝑥 100 Optical Analyses of Semiconductors/PP Composite Materials S4 The UV-Vis-NIR diffuse reflectance of the pristine PP, silver-based ternary oxides, and PP modified with Ag-based ternary oxide are shown in Figure S1. In the Figure S1A and S1B, the samples containing the fillers of wide band gap do not exhibit clearly absorptions due to the presence of the additives α-Ag2WO4 and β-Ag2MoO4, respectively, but there are significant changes in the total diffuse reflectance of incident radiation and in the color of the samples (Table S1). On the other hand, the incorporation of the Ag2CrO4 is evident to PP modification, which show absorptions near to band gap of the pristine metal oxide. Furthermore, the band absorptions at 1200, 1400, and 1730 nm are characteristic of the 2nd overtone, 1st overtone combination, and 1st overtone due to the C-H single bond vibration absorption,1 which is in agreement with the literature.2 The highest decrease in the total diffuse reflectance is observed in the samples containing 3% of fillers, where the observed changes in the absorption attributed to the 2nd overtone and 1st overtone combination for C-H single bond vibration.1 It is believed that is due to the change in the chain structure of the polymer. Only the PP samples modified with βAg2MoO4 keep their structure. S5 Figure S1 - Diffuse reflectance spectrum to the silver based ternary oxides, pristine PP and PP modified with (A) α-Ag2WO4, (B) β-Ag2MoO4, and (C) Ag2CrO4. 300 600 900 1200 1500 1800 2100 0 20 40 60 80 100 Ag2 CrO4 PP PPAC05 PPAC1 PPAC3 Rd / % Wavelength / nm 300 600 900 1200 1500 1800 2100 0 20 40 60 80 100 Ag2MoO4 PP PPAM05 PPAM1 PPAM3 Rd / % Wavelength / nm 300 600 900 1200 1500 1800 2100 0 20 40 60 80 100 Ag2WO4 PP PPAW05 PPAW1 PPAW3 Rd / % Wavelength / nm AB C S6 Table S1 – Digital images for the PP, PPAW, PPAM and PPAC samples. % added to the polymer (in weight) Composite Pristine 0.5% 1.0% 3.0% PP α-Ag2WO4 β-Ag2MoO4 Ag2CrO4 The radiation absorptions observed in the ultraviolet-visible spectrum can be ascribed to the transitions from HOMO to LUMO of polymer and from the valence to the conduction bands of the silver-based ternary oxides. In the Figure S1 it is observed that the polymer matrix shows a decrease in the total diffuse reflectance spectrum around 350 nm, which is associated with -∗ transitions from the carbonyl groups originated by oxidation of PP.3,4 Further, the pristine silver-based ternary oxides display absorptions around 410, 380, and 740 to α-Ag2WO4, β-Ag2MoO4, and Ag2CrO4, respectively. The band gap energies (Eg) were experimentally estimated by extrapolating the linear portion of the Tauc plot curves, which are shown in the Figure S2. Although the pristine α-Ag2WO4 and β-Ag2MoO4 have Eg smaller than the transition HOMO-LUMO of the polymer, the modified PP samples with these materials’ present values of Eg near to transition observed for pure PP. It can be associated with the indirect transition behavior of the mechanism of excitation of these metal oxides,5 which could bring a superposition of the interband transition of the metal oxide with the HOMO-LUMO transition of the polymer. In this way, the Tauc plot curve show just one transition. However, as the percentage of metal oxides increases in the polymer matrix, the bandgap decreases trending to the value of pristine metal oxides. Regarding the PP modified with Ag2CrO4, the Eg values were similar to the metal oxides.5 In this latter case, the narrow S7 Eg of the metal oxide does not overlap with the HOMU-LUMO transition of the PP, which allows the clear observation of the changes in the Tauc plot (Figure S2). It is noteworthy to mention that the values of the Eg estimated for the pristine metal oxide are in agreement with those reported in the literature.5 Figure S2 – Tauc plot to the (A) PP, (B) PPAW, (C) PPAM, and (D) PPAC. The arrows indicate the band gap energy in the materials with indirect band gap, while the band gap for direct transitions is the linear extrapolation crossing the X axis. Figure S3 shows the Raman spectra obtained for the samples. In all samples it is possible to observe the peaks of the polypropylene polymer matrix. Between 950 and 1500 cm-1 it is possible to observe the Raman modes related to the deformation and stretching vibration modes of the -CH2 and -CH3 groups of the PP skeleton.6 In the regions between 2700 and 3000 cm-1, the modes related to the bending vibrations of the -CH2 groups are observed.6 On the other hand, it is possible to differentiate the samples due to the presence of specific Raman modes of the α-Ag2WO4, β-Ag2MoO4 and Ag2CrO4. For the PPAW samples, it is possible to observe an A2g mode around 875 cm-1 related to the stretching of the [WO4] clusters.7 In the PPAM samples, an A1g mode located at 873 cm1 is also observed, related to the symmetrical stretching of the [MoO4] clusters.8 In the case of PPAC samples, two characteristic Ag modes are observed at 770 and 805 cm-1, 1.5 2.0 2.5 3.0 3.5 4.0 [F(Rd)h] 2 / a.u. h / eV PP 1.5 2.0 2.5 3.0 3.5 4.0 Ag2CrO4 1.85 eV 1.90 eV PPAC05 [F(Rd)h] 2 / a.u. 1.88 eV PPAC1 1.78 eV PPAC3 h / eV 1.5 2.0 2.5 3.0 3.5 4.0 Ag2MoO4 3.31 eV PPAM05 3.48 eV [F(Rd)h] 1/2 / a.u. PPAM1 3.48 eV PPAM3 3.45 eV h / eV 1.5 2.0 2.5 3.0 3.5 4.0 Ag2WO4 3.11 eV PPAW05 [F(Rd)h] 1/2 / a.u. 3.71 eV PPAW1 3.68 eV PPAW3 h / eV 3.61 eV AB CD S8 related to the stretching of the [CrO4] clusters.9 In this way, as in the XRD and FTIR analyses, it can be observed that the structures of the polymer and the Ag-based semiconductors are maintained even after the formation of the composites. Figure S3 – Raman spectra of the (A) PPAW, (B) PPAM, and (C) PPAC samples. 500 1000 1500 2000 2500 3000 3500 Raman shift (cm-1) Normalized intensity (units arb.) PPAW3 PPAW1 PPAW05 PP A B C 500 1000 1500 2000 2500 3000 3500 PPAC3 PPAC1 PPAC05 PP Raman shift (cm-1) Normalized intensity (arb. units) 500 1000 1500 2000 2500 3000 3500 Normalized intensity (arb. units) Raman shift (cm-1) PPAM3 PPAM1 PPAM05 PP S9 Figure S4 - Storage (G′) and loss modulus (G″) of PPAW (A), PPAM (B) and PPAC (C) samples at 190° C as a function of frequency.