Evaluation of Low Velocity Impact Response of

Mechanics, Materials Science & Engineering, Vol. 16 2018 – ISSN 2412-5954

Reduction of 4-Nitrophenol and Production of 4-Aminophenol at Ambient Conditions by Sterculia Acuminata Fruits Extract Mediated Synthesized Platinum Nanoparticles 1

N.K.R. Bogireddy1, H.A.K. Kumar1, B.K. Mandal1, a 1 – Trace Elements Speciation Research Laboratory, Department of Chemistry, School of Advanced Sciences, VIT University, India a – [email protected] DOI 10.2412/mmse.8.72.956 provided by Seo4U.link

Keywords: Sterculia acuminata, 4-nitrophenol, platinum nanoparticles, catalytic activity.

ABSTRACT. A biosynthesized platinum nanoparticles (PtNPs) using aqueous fruit extracts of S. acuminata is demonstrated in this report. Here, multifunctional plant extracts played a major role in synthesizing PtNPs from its salt. Initially PtNPs was confirmed by UV-visible absorbance spectroscopy, the Face centered cubic structure and amorphous in nature was identified by X-ray diffraction analysis and SAED image from transmission electron microscopy. The average size of nanoparticle is calculated around 3.4 nanometers from TEM and revealed by Dynamic light scattering analysis. Demonstrated the functional groups present in extract and NPs using FT-IR analysis. Furthermore, to know the active polyphenols in the extract, HPLC technique is used. Moreover, These PtNPs showed good catalytic efficiency towards the decolorizing of organic pollutant (4-nitrophenol (4-NP)).

Introduction. Nanotechnology has turned into a vital zone for logical advancement in material science, bio-medicine and catalysis [1-3]. In this scenery metal nanoparticles (Pt, Ag, Au and PdNPs) (MNPs) show some unique features, those are specially interrelated to the size and shape of the particle. As of late, MNPs have been centered by scientists having a place with various distinct features in optoelectronic and physicochemical properties that are fundamentally not quite the same as those of bulk materials [4-7]. Various techniques for the preparation of nanoparticles are accounted, by chemical reducing agents [8– 14]. But the utilization of such reducing agents causes ecological harmfulness, requires additional toxic stabilizing agents which causes environmental toxicity. Hence, there should be a raise in the development of eco-friendly synthesis of NPs through environmentally suitable synthetic procedures based on 12 fundamental principles of green chemistry [15, 16]. The negative impact of the reducing agents gives path to biological (green) synthesis method of nanomaterials to promote distinctive natural materials. Among the biological techniques plants have been promoted generally and proficiently for wide scale synthesis of nanoparticles, which are eco-friendly. Various reports are accessible on the preparation of NPs, by using several parts of the plants [17-21] and also showed multifunctional capacity like both reduction and capping capacity of plants, source of the plant extract is impact the features of the NPs is well known [22]. Recent days, the activity of MNPs in the catalysis having more susceptible scopes. 4-nitrophenol is widely recognized natural anthropogenic contamination in agriculture and industrial waste water. These organic pollutant is toxic in nature and it may harmful to skin, kidney and liver diseases, and moreover, harming to the nervous system in people and creatures [23]. So much consideration has been given to build up an effective procedure for the decolorization of 4-NP and production of 4aminophenol (4-AP). Herein PtNPs was synthesized using S. acuminata (S.A.) fruits extract as

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© 2018 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

MMSE Journal. Open Access www.mmse.xyz


multifunctional agent and its catalytic efficiency was checked in the decolorization of organic pollutant (4-NP). Also, reduction kinetics of 4-NP was monitored with time using PtNPs as catalyst. Materials and methods. Materials. Chloroplatinic acid (H2PtCl6), sodiumborohydride (NaBH4) and 4-Nitrophenol were purchased in Sigma Aldrich, India. Preparation of extract using S. Acuminata fruits. S. A. fruits were gathered from university campus. The fruits husk was removed, dehydrated and kept in atmosphere circumstances. For the study of extract, 1g of S.A. fruits powder was dispersed in 100mL of distilled water at 900C for 35 min. The freshly prepared S.A. fruits extract was filtered and finally extract was stored in refrigerator for further analysis Synthesis of Platinum nanoparticles. For the preparation of PtNPs using S.A. fruits extract, in the addition of 30 mL platinum precursor (0.01M) to 150mL S.A. fruits extract. Here we are using reflection method (using magnetic heater and condenser) to preparation of PtNPs. Successively, the development of PtNPs was observed color transformation from pale yellow to black color. Characterization of synthesized PtNPs. The preliminary characterization of synthesized Pt NPs was performed by Jasco V-670, UV-vis absorption spectrophotometer. XRD study was carried out by using Bruker D8 Advance Diffractometer. For the examination of crystallinity and size of PtNPs were done by HRTEM (JEOL JEM 2100). To measure average particle size and charge of NPs, DLS or Zeta-sizer (Horiba scientific nanoparticci, nanoparticle analyzer, SZ-100) was used. To know the functional groups present in purified PtNPs with control of S.A. fruits powder, FT-IR measurements were done (Shimadzu IR AFFINITY-1 instrument). Furthermore, to find out the active Phytoconstituents in the reduction of Pt, HPLC (Perkin Elmer HPLC, with column C18PCX). Catalytic efficiency of PtNPs. Efficiency of synthesized PtNPs was tested by decolorizing the 4-NP with NaBH4 as reducing agent. For 4-NP reduction, freshly prepared 1mL of 0.2 M NaBH4 aqueous solution was mixed with 4mL of 0.1 M 4-NP solution in reaction tube. Then different concentrations (10 µL–100 µL) of synthesized Pt NPs dispersion were added to above reaction tube. Progress in the reaction was noticed by observing color difference from pale yellow to colorless and also spectra was recorded using absorbance spectroscopy. Results and Discussion. Optimization of PtNPs.



Fig. 1. UV-Visible spectra of synthesized PtNPs and inset (H2PtCl4 and Extract). PtNPs were synthesized by reducing platinum salt (Pt+4) with aqueous S.A. fruits extract. Initially, PtNPs formation act identified by solution intensity transformation indistinction to the pale to dark black solution within 30 min. UV-vis absorbance analysis of the PtNPs showed in Fig. 1. The absorption peak (λmax) of precursor (platinum salt) was observed at 262 nm, but after the formation of PtNPs there is no precursor absorbance peak, which signifying the reduction of platinum precursor to PtNPs (Fig. 1).

Fig. 2. X-ray diffraction pattern of synthesized PtNPs (A), HR-TEM images of PtNPs at different magnifications (B, C and D) and SAED pattern (E). MMSE Journal. Open Access www.mmse.xyz


From the X-ray diffraction results are evidence for synthesized PtNPs was amorphous with distinct peak patterns at 39.820, 46.400, 67.730, 81.450 and 85.900 respectively, which could be corresponding miller indices as (111), (200), (202), (311) and (222) respectively (Fig. 2, a). These planes are corresponding to FCC of PtNPs and matched with database of JCPDS (JCPDS No: 96901-958). The HR-TEM results showed that the synthesized PtNPs were irregular spherical with good dispersion, the average size of NPs was calculated ~3.4 nanometers (Fig. 2 (b-d)). The fringe space of particles is measured 2.273A0, which is good conformity with (111) plane spacing of FCC PtNPs (2.2608A0) (JCPDS: 96-901-958). The SAED pattern of synthesized PtNPs was good agreement with XRD results (Fig. 2, e).

Fig. 3. Average particle size (a) Zeta potential of synthesized PtNPs (b) and FTIR spectra of synthesized PtNPs before reduction (c). The average size of PtNPs were revealed DLS analysis with 3.4 nm (Fig. 3, a), which is clear conformity with TEM reports and the stability of NPs was revealed by zeta potential studies with 29.2 mV (Fig. 3, b). The more negative surface charge of particles due to stabilization of NPs with polyphenols those are from S.A. extract. From the FT-IR analysis, IR bands were observed at 3176.76, 2935.66, 1737.86, 1631.78, 1445, 1389.46, 1201 and 1037.70 cm−1 (Fig. 3, c). The bands appeared at 3176.76, 2935.66 and 1737.86 cm−1 are related to hydroxyl stretching, aliphatic –C–H and –C=O, and 1631.78, 1445, 1389.46 and 1037.70 cm−1 respectively are corresponds to –C–C, – C–N, –C–O and –C–O–C respectively. Finally, in IR spectra at 1205 cm−1 is corresponds to –C–O– H bending. Plausible mechanism.



Fig. 4. Plausible mechanism involved in the synthesis of stable PtNPs. In generally naturally available reducing agents having secondary metabolites in the form of polyphenols. These secondary metabolites are nothing but Active phyto-constituents partaking in the reduction of platinum precursor with S.A. fruits extract was identified by HPLC analysis. From the analysis 4 significant peaks with retention times 3.36, 3.12, 2.61 and 2.30 min respectively was identified, these are corresponding to methyl gallate (MG), pyrogallol (Py), gallic acid (GA) and ascorbic acid (AA) respectively under room temperature. These retention times are good conformity with standard solutions of methyl gallate (MG), pyrogallol (Py), gallic acid (GA) and ascorbic acid (AA) solutions shown in supplementary Fig. 2. When compared with standard solutions a small shift in the retentions times because of the matrices differs in the S.A. fruits extract. Moreover, all the identified active compounds have at least 3 -OH groups. These -OH groups are influence the precursor (H2PtCl6), there will be reduction of platinum precursor to PtNPs, and at the same time all the polyphenols convert in to individual oxidized/quinine forms. Similarly, carbonyl group presence in quinine forms favors synchronization on to freshly shaped PtNPs and ensuing the growth of capping. Due to the electrostatic interaction between soft ligands and metal precursor there is complex formation of capping on to surface of NP. Here, quinine form of GA plays vital performance in the capping of NPs by reason of existence of carboxylic group, but the quinines of AA is not stable in solution due to its electrophilic in nature ensuring immediate evolution of polyhydroxy complex finished with inevitable hydrolysis [24]. Whereas in MG not participating in the capping of NPs, because the existence of methylene groups. Similarly, Py is participating in reduction process but not participating in the capping process with lack of available -C=O groups. From HPLC analysis revealed secondary metabolites are participated in the reduction and GA quinine forms involved in the stabilization of PtNPs as well. So, GA showing multifunctionality nature in the formation of PtNPs (Fig. 4).



Fig. 5. Catalytic efficiency of synthesized PtNPs (A) and Kinetics of catalytic reduction of 4nitrophenol by PtNPs (B). Catalytic activity. Catalytic reduction of organic pollutants using MNPs is emerging technology in recent days [26]. Here, In order to identify the efficiency of PtNPs as catalyst in the decolorization of 4-NP to 4-AP using NaBH4. The decolorization of 0.1M 4-NP using 0.2M NaBH4 with the presence of catalyst. With the addition of NaBH4 to the 4-NP, observed a color change from pale to dark yellow (indicates the evolution of 4-NP ion). The UV-visible spectra confirmed peak absorbance peak change from around 300 (4-NP) to 400nm (4-NP ion). Without addition of catalyst there is no change in the absorbance of 4-NP ion, after the involvement of 30µL of Pt colloid, there is a drastic change in the absorbance. In one hand, the absorbance of 4-NP ion decreasing which signifies the reduction of 4-NP ion and similarly other hand there is an evolution of new absorbance peak at around 310nm which signifies the formation of 4-AP. Finally, within 8 min the vanishing of dark yellow of 4-NP ion to formation of 4-AP color less solution (Fig. 6, a). Here, the concentration of BH-4 is remains unchanged throughout the probe but it is more in concentration when it compares with 4-nitrophenol concentration. However, the rate constant (k =6.16*10-3 min-1) of reaction depends on the quantity and particle size plays influential vital role on the PtNPs (Fig. 5, b). Summary. A simple biological approach for the preparation of PtNPs using S.A. fruits extract. The multifunctional nature of extract was identified by FTIR and mechanism was illustrated using active Phyto-constituents from HPLC analysis. The morphology with average size distribution of around 3.4nm and surface charge of the PtNPs were identified from high resolution-Transmission electron microscopy, dynamic light scattering and zeta potential results. Furthermore, miller indices and plane spacing was revealed from X-ray diffraction and selected area diffraction pattern, those are matched with JCPDS file. Synthesized PtNPs showed an excellent catalytic efficiency towards the reduction of 4-Nitrophenol and the formation of 4-aminophenol. This synthesis method more prolonged to other NPs like Au, Pd and Ag respectively and degradation of more industrial organic pollutants like Methylene blue, Methylene orange, Phenol red etc. References [1] C. Burda, X. Chen, R. Narayanan, M.A. El-Sayed, Chemistry and Properties of Nanocrystals of Different Shapes, Chem. Rev., 2005, DOI 10.1021/cr030063a. [2] R.A. Sperling, P. Rivera-gil, F. Zhang, M. Zanella, W.J. Parak, Biological applications of gold nanoparticles, Chem. Soc. Rev., 2008, DOI 10.1039/B712170A. MMSE Journal. Open Access www.mmse.xyz


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