Additional data on the investigation of the reaction mechanisms for the production of silica hyperbranched polyethylene imine silver nanoparticle composites

Silica-organic matrix-silver, nano-catalysts, were synthesized employing four different hyperbranched poly(ethylene imines) (MW 2000 to 750,000) to reduce Ag+ to metal nanoparticles and the formation of formation SiO2 shells. The latter is performed at pH 7,5 employing three different pH regulating agents Hepes, Trizma, and Phosphate Salts. Characterization of the resulting materials with spectroscopy (FTIR), thermogravimetry (TG), scanning electron microscopy (SEM), and ζ-potential is reported. Kinetic studies of standard reactions, 4-nitrophenol and 4-nitroaniline reduction to 4-aminophenol and p-phenylenediamine, respectively by UV-Visible spectroscopy are also included. This data in brief article is related to the “Investigation of two Bioinspired Reaction Mechanisms for the Optimization of Eco Composites-Nano Catalysts Generated from Hyperbranched Polymer Matrices” manuscript submitted to reactive & functional polymers.


Value of the Data
• SEM micrographs provide correlation on composites shape/size in relation with the preparation method. • Every researcher in fields relative to composite materials could take advantage of the reported data. • These data may be used for the development of similar composite catalysts with other metals and shells. • Thermogravimetry Data provide important information on the material's composition. Table 1 explains the nomenclature of the samples: the numbers represent the MW of hyperbranched poly(ethylene imine) P, T, H represents the pH regulating agent, Ag the presence of silver, and C the optional calcination step. Figs. 1-15 are representative SEM micrographs of PEI-silica composite nanospheres and PEI-silica-Ag nanocatalysts. Figs. 16-26 are TGA results and the respective 1st derivatives of PEI-silica nanospheres and PEI-silica-Ag nanocatalysts. Raw Table 1 Sample classification according to the MW of PEI, the buffering agent, the presence of Ag, and the employment of an optional calcination step at 700 °C 'modified from [1] .

PEI-Silica Nanospheres Mw
Phosphates             data are publicly available on the Mendeley Data repository https://data.mendeley.com/datasets/ 22symh9gs4/1 [5] . Fig. 27 is a diagram of the w/w% compositions of the PEI-silica nanospheres and the PEI-silica-Ag nanocatalysts (raw data values included in the diagram). Fig. 28 contains the nitrophenol and nitroaniline reduction rate coefficients and Table 2 contains the raw data.

Instrumentation
Scanning Electron Microscopy (SEM) micrographs were obtained with the aid of a FEI Inspect microscope with W (Tungsten) filament. UV-Visible spectroscopy for the calculation of the catalytic reduction constants was carried out on a Cary 100 UV-visible spectrophotometer. Thermogravimetric analysis experiments (TGA) under nitrogen flow were performed on a Mettler Toledo TGA/DSC 1 System)(heating rate: 10 °C/min).

Reduction of Silver Cations to Ag Nanoparticles
To 100 ml solutions of PEIs 0.1 mM (approximately 40 mM in primary and secondary amines, 25 ml of AgNO 3 0.1 M were added under stirring. The samples remained colorless for the first hour of the experiment at the end of which a slight change to light orange was observed, indicating the beginning of the formation of Ag nanoparticles. The samples were kept under stirring for 8 days, a period followed by a gradient change regarding their color from colorless to dark brown. This procedure was applied for the four different types of PEI with molecular weights of 20 0 0, 50 0 0, 25,0 0 0, and 750,0 0 0.

Synthesis of SiO 2 -PEI-Ag Nanocatalysts
The second reaction involved the formation of SiO 2 based on the method proposed by Knecht and Wright [2] modified by our group [3] . 100 ml of each Ag-PEI solution acquired from the first step, was brought to pH 7,5 employing phosphates, Trizma or Hepes, and the conjugate hydrochloride and sodium salts of the latter, respectively. Silver salts, of the pH regulators, when precipitated by non-reduced Ag + , were removed by centrifugation. Then, 10 ml of 1 M silicic acid, prepared from the hydrolysis of tetraethyl orthosilicate in 5 mM HCl, were added. Brown precipitates were immediately observed. The samples were centrifuged (10 min 12,0 0 0 x g), washed twice with water, and the supernatant was decanted. The final step involved a mild drying of the samples under vacuum over P 2 O 5 . Silica silver nanocatalysts (i.e., without the organic matrice) were obtained by calcination for 3 h at 700 °C under nitrogen. Furthermore, silica-hyperbranched poly(ethylene imine) composites (i.e., without silver nanoparticles) were produced in 20 mM phosphate, trizma, and hepes buffers. Table 1 c ontains the classification and nomenclature of all the synthesized materials.

Catalytic Performance Tests
The catalytic properties of the SiO 2 -PEI-Ag nanocatalysts and their calcinated counterparts were assessed by the aid of two standard nitroaromatic compound reduction reactions. The conversion of 4-nitrophenol to 4-aminophenol and 4-nitroaniline to p-phenylenediamine [4] . 5 mg of each sample were dispersed to 50 ml of a 8 ppm aqueous solution of each nitro derivative and then an excess of NaBH 4 (generally 10 mg) was added. The reaction was monitored at room temperature under continuous stirring by UV-Visible spectroscopy.

Ethics Statement
The work does not involve human subjects, animal experiments, or data collected from social media platforms.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships which have or could be perceived to have influenced the work reported in this article.