Nagwa El-Desouky

Kamel R Shoueir
email: rezkshoueir@unistra.fr

Ibrahim El-Mehasseb

Maged El-Kemary
email: elkemary@nano.kfs.edu.eg

Bio-inspired green manufacturing of plasmonic silver nanoparticles/Degussa using Banana Waste Peduncles: Photocatalytic, antimicrobial, and cytotoxicity evaluation

Keywords: Green fabrication, photocatalytic, silver nanoparticles/Degussa, antimicrobial, cytotoxicity

de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

2

With the growth of the industrialization and the development of modern technology, serious environmental pollution induced by toxic heavy metals as chromium (VI) and organic pollutants as dyes in water and wastewater has been reported to cause health problems [START_REF] Xu | Enhanced photocatalytic reduction of Cr (VI) by Cu2O/Bi5O7I microrods composites under visible light[END_REF][START_REF] Qin | Improving the photocatalytic hydrogen production of Ag/gC3N4 nanocomposites by dye-sensitization under visible light irradiation[END_REF]. Chromium (Cr) is a heavy metal that mainly exists in two oxidation states, Cr(III) and Cr(VI) and Cr(VI) is approximately 100 times more toxic than Cr(III), which may cause renal and liver failure and various types of cancer [START_REF] Zhitkovich | Importance of chromium-DNA adducts in mutagenicity and toxicity of chromium (VI)[END_REF][START_REF] Wu | Photocatalytic reduction of Cr (VI) with TiO2 film under visible light[END_REF]. Methylene blue (MB) as a cationic dye is one of the most widely used in the textile industry, is one of the pollutants in an aqueous environment, that cause multiple diseases, such as cancer, gastrointestinal ulceration, nephritis, liver, kidney and human reproductive dysfunction [START_REF] Liu | One-step synthesis of a WO3-CuS nanosheet heterojunction with enhanced photocatalytic performance for methylene blue degradation and Cr (VI) reduction[END_REF][START_REF] Ahsan | Adsorptive removal of methylene blue, tetracycline and Cr (VI) from water using sulfonated tea waste[END_REF].

Hence, the removal of organic and inorganic pollutants from wastewater is necessary before discharging them into the environment and to reuse water due to increasing water demand. Several conventional approaches have been proposed for water/wastewater treatment, including adsorption, catalytic degradation, biodegradation, flocculation, coagulation, sedimentation, and membrane filtration. Among them, photocatalysis, especially heterogeneous photocatalysis has emerged as an effective and inexpensive tool for water and wastewater treatment [START_REF] Shoueir | Tailoring the surface reactivity of plasmonic Au@ TiO2 photocatalyst bio-based chitosan fiber towards cleaner of harmful water pollutants under visible-light irradiation[END_REF][START_REF] Shoueir | Fenton-like nanocatalyst for photodegradation of methylene blue under visible light activated by hybrid green DNSA@ Chitosan@ MnFe2O4[END_REF][START_REF] Bumajdad | Nanostructured mesoporous Au/TiO2 for photocatalytic degradation of a textile dye: the effect of size similarity of the deposited Au with that of TiO2 pores[END_REF][START_REF] El-Kemary | Photocatalytic degradation of ciprofloxacin drug in water using ZnO nanoparticles[END_REF][START_REF] El-Kemary | Sol-gel TiO2 decorated on eggshell nanocrystal as engineered adsorbents for removal of acid dye[END_REF][START_REF] El-Shafai | Graphene oxide-metal oxide nanocomposites: fabrication, characterization and removal of cationic rhodamine B dye[END_REF][START_REF] El-Shafai | Fabrication and characterization of graphene oxide-titanium dioxide nanocomposite for degradation of some toxic insecticides[END_REF][START_REF] El-Shafai | Magnetite nano-spherical quantum dots decorated graphene oxide nano sheet (GO@ Fe3O4): Electrochemical properties and applications for removal heavy metals, pesticide and solar cell[END_REF][START_REF] El-Kemary | Enhanced photocatalytic degradation of Safranin-O by heterogeneous nanoparticles for environmental applications[END_REF][START_REF] El-Sheshtawy | Activated H2O2 on Ag/SiO2-SrWO4 surface for enhanced dark and visible-light removal of methylene blue and p-nitrophenol[END_REF]. Photocatalysis technology as one of the advanced oxidation processes has progressed rapidly since the discovery of photoelectrochemical water splitting reaction using semiconductor [START_REF] Fujishima | Electrochemical photolysis of water at a semiconductor electrode[END_REF].

Recently, plasmonic AgNPs fabricated by green approaches have more merits than others mentioned routes owing to the presence of several biologically active components [START_REF] Abdelbar | Halogen bond triggered aggregation induced emission in an iodinated cyanine dye for ultra sensitive detection of Ag nanoparticles in tap water and agricultural wastewater[END_REF]. The secret lies in the presence of reducing features as well as stabilizing agents such as general polysaccharides, terpenes, polyphenols, vitamins, etc. [START_REF] Hemmati | Green synthesis and characterization of silver nanoparticles using Fritillaria flower extract and their antibacterial activity against some human pathogens[END_REF][START_REF] Paul | Role of surface plasmons and hot electrons on the multi-step photocatalytic decay by defect enriched Ag@ TiO2 nanorods under visible light[END_REF], with higher cytotoxicity and antibacterial performance [START_REF] Aslany | Characterization and Evaluation of Cytotoxic and Apoptotic Effects of Green Synthesis of Silver Nanoparticles Using Artemisia Ciniformis on Human Gastric Adenocarcinoma[END_REF]. In this regard, biogenic synthesis of metallic nanoparticles has therefore attracted increasing attention over the last decades, in parallel with the increased interest in green chemistry and sustainability [START_REF] Dhand | Green synthesis of silver nanoparticles using Coffea arabica seed extract and its antibacterial activity[END_REF]. In particular, green synthesis using plant extracts, bacteria, fungus, and algae was validated as a capping and stabilizing agent [START_REF] Hemmati | Green synthesis and characterization of silver nanoparticles using Fritillaria flower extract and their antibacterial activity against some human pathogens[END_REF][START_REF] Sharma | Biogenic synthesis of nanoparticles: A review[END_REF].

Bananas are consumed all over the world with huge quantities and the peels were discarded.

On the other side, a few publications highlighted their applications in different areas such as the production of laccase [START_REF] Cruz | Banana skin: a novel material for a low-cost production of laccase[END_REF], producing fungal biomass [START_REF] Deokar | Green synthesis of gold nanoparticles (Elixir of Life) from banana fruit waste extract-an efficient multifunctional agent[END_REF], in the medicinal part [START_REF] Gopi | Novel banana peel pectin mediated green route for the synthesis of hydroxyapatite nanoparticles and their spectral characterization[END_REF]. Otherwise, the peels are inherently rich in polysaccharides, pectin, cellulose derivative, and a small amount of lignin which add value to functionality during wastewater remediator [START_REF] Cordeiro | Chemical composition and pulping of banana pseudo-stems[END_REF]. The presence of active constituent in extracts are different from plant to another consisting of polyphenols, essential oil, glucosides, unsaturated sterols etc. But this part if it kept away in the open air it completely decomposed to more deteriorated organic substance led to a rotten surrounded environment. So, one of our goals is squeezing of banana waste peduncles (BWP) in the form of extracted juice to elevate the benefit of the peel as a whole.

In the area of water treatment and infection, AgNPs/Degaussa nanocomposites are validated as a photocatalytic activity against degradation, reduction, antibacterial, and cytotoxicity properties [START_REF] El-Shabasy | A green synthetic approach using chili plant supported Ag/Ag2O@ P25 heterostructure with enhanced photocatalytic properties under solar irradiation[END_REF][START_REF] Sangaonkar | Garcinia indica mediated biogenic synthesis of silver nanoparticles with antibacterial and antioxidant activities[END_REF]. 3D Ag2O@TiO2 was fabricated by assembling Ag2O (p-type) onto TiO2 (ntype) to produce microspheres and used to enhance the degradation of methyl orange [START_REF] Sarkar | Three dimensional Ag2O/TiO2 type-II (p-n) nanoheterojunctions for superior photocatalytic activity[END_REF].

Another study depicted that Ag2O/TiO2 quantum dots in a spherical shape with good photocatalytic decomposition activity up to 80% of levofloxacin at acidic media compared with plain TiO2 [START_REF] Kaur | Visible light driven photocatalytic degradation of fluoroquinolone levofloxacin drug using Ag2O/TiO2 quantum dots: a mechanistic study and degradation pathway[END_REF]. Besides, and according to synthetic procedures, AgNPs standalone was used as antibacterial using Berberis vulgaris leaf aqueous extract [START_REF] Behravan | Facile green synthesis of silver nanoparticles using Berberis vulgaris leaf and root aqueous extract and its antibacterial activity[END_REF]. Also, AgNPs were deposited onto P25 with high dispersion via precipitation reaction and the presence of cold plasma treatment and applied for photocatalytic and antibacterial property [START_REF] Dong | Plasmon enhanced photocatalytic and antimicrobial activities of Ag-TiO2 nanocomposites under visible light irradiation prepared by DBD cold plasma treatment[END_REF]. But the unique features of nanoparticles required both nanosized and dispersed particles without aggregation and without rigorous experimental conditions as for the previously mentioned Ag/TiO2 heterostructure not included. Besides, some of those focused on the photocatalytic process under UV light which hindered its photocatalytic applications [START_REF] Xekoukoulotakis | UV-A/TiO2 photocatalytic decomposition of erythromycin in water: Factors affecting mineralization and antibiotic activity[END_REF]. So far, plasmonic nanostructured increase the photocatalytic property under solar irradiation by lowering the activation energy [START_REF] Yan | Au/BiOCl heterojunction within mesoporous silica shell as stable plasmonic photocatalyst for efficient organic pollutants decomposition under visible light[END_REF][START_REF] Zhang | Plasmonic Cu nanoparticle on reduced graphene oxide nanosheet support: An efficient photocatalyst for improvement of near-infrared photocatalytic H2 evolution[END_REF][START_REF] Huang | Selective deposition of plasmonic copper on few layers graphene with specific defects for efficiently synchronous photocatalytic hydrogen production[END_REF].

Herein, we report the development of a facile and sustainable approach for green fabrication of plasmonic AgNPs and AgNPs/Degussa nanocomposite to avoid the toxicity generated by the chemical compounds used for NPs fabrication. P25 was grown on the surface of plasmonic AgNPs by microwave synthesis. This is the first report about photocatalytic and antimicrobial activities of AgNPs by using Banana Waste Peduncles (BWP) extract from original waste which also analyzed by HPLC to detect the activity of reducing groups. The resulting hybrid (nanocomposite) was used for degradation of methylene blue (MB) textile dye and the photoreduction reduction of Cr(VI) via visible-light-driven catalytic reaction, in addition to the inactivation of gram-positive and gram-negative bacteria with anticancer effectiveness.

Methodology

Collection and extraction procedures of banana waste peduncles (PWP)

The BWP was freshly picked from a local market (center of Kafrelsheikh Governorate, Egypt), thoroughly cleaned with running tap water for 10 min to eliminate all dust and unwanted particles. Then, the BWP vine-ripened and cut into small cubes soaked in DDI followed by squeezing the small cubes to get the extracted juice filtered by fine pores nylon mesh then Whatman filter paper (0.45 μm). The extracted juice was collected to eliminate visual impurities was centrifuged thrice at 6,000 rpm for 15 min. The extract was ready for subsequent experiments.

One-pot microwave preparation of bio-inspired AgNPs/Degussa

Typically, 100 mL of the prepared BWP juice extract was equally added to 100 mL solution of 2mM AgNO3 (Molecular weight, 169.87 g/ mol, pure white crystal, ACS reagent ≥ 99.0%) to a Teflon-lined STRT SYNTH microwave oven (WX-4000) with the following parameters: 1.1 Par, 60% stirring, 600 watts, temperature 70 o C, and equilibrium time 20 min). Followed by adding 5 mg Degussa (TiO2, Degussa Anatase, Rutile: 75:25, 99.9%, and 20 nm) in the same solution, the whole solution was transferred again to the microwave oven with the same previous parameters. Finally, the obtained AgNPs/Degussa nanocatalyst was centrifuged to separate the faint brown powder which was washed at least three times with DDI then twice by absolute ethanol. The obtained nanocatalyst was dried at 60 o C overnight to produce a fine pure powder from nanocomposite AgNPs/ Degussa.

Phytochemical screening test

Phytochemical screening of Banana Waste Peduncles extract was carried out to examine the active components by using of a standard method [START_REF] Hamedi | Rapid and green synthesis of silver nanoparticles using Diospyros lotus extract: Evaluation of their biological and catalytic activities[END_REF].

Identification and quantification of phenolic compounds by HPLC

High performance liquid chromatography (HPLC) analysis was performed for the identification of the bioactive phenolic compounds in Banana Waste Peduncles extract. The experiment was carried out using direct control of Shimadzu LC-10 and LC-20 (Prominence) series using Clarity Chromatography Software. The separation technique used C18 column as stationary phase with specification; (150 mm x 4.6 mm i.d., particle size 5µm) and the temperature of the column was controlled at 30 o C. On the other hand, 0.2% (v/v) phosphoric acid as mobile phase A and HPLC grade acetonitrile as mobile phase B was used as chromatographic separation detector. The injected volumetric sample was 10µl at 65 min and the multi-wavelength was maintained at 280nm during the analysis.

Characterization

The characterizations of the spectra of the as-synthesized samples were implemented by using a UV 2600 Spectrophotometer (Shimadzu, Japan) and FTIR spectrometer (JASCO FTIR/6000, Europe). The powder X-ray diffraction (XRD) patterns of the samples were obtained on an ADVANCE Brucker D8 diffractometer (Philips X' Pert Modular Powder Diffractometer) with Cu Kα radiation (λ = 1.5418 Å). High-resolution Scanning electron microscope (HR-SEM) micrographs were taken on (HR-SEM QUANTA FEG250, Japan). The Transmission electron microscope (TEM) images of the samples were obtained from Field Emission Transmission Electron Microscope (FETEM, JEM-2100F, (Japan), operated at an accelerating voltage of 200 kV.

Photocatalytic activity tests

The photocatalytic activity of plasmonic AgNPs and AgNPs/Degussa was investigated by the photodegradation of MB dye (10 mg/L, pH = 7.0) and photocatalytic reduction of Cr(VI) at room temperature under visible light irradiation. In a typical photodegradation experiment, ~5 mg of the photocatalyst powder is the optimal dosage between 1, 3, and 7 mg so it is used along the experiment, then this dosage was added to 15 ml aqueous suspension of MB in a 50 mL beaker and the system was magnetically stirred during the photodegradation.

For photoreduction of Cr(VI) under visible light irradiation, the stock solution was prepared from citric acid (ACS reagent, ≥ 99.5%, 8mL), and then 4 mL of it was added to 16 mL of 10 mg/L potassium dichromate (VI) (K2Cr2O7) to acidify the solution. The remaining concentration was detected by double-beam UV-vis and the degradation percentage D (%) was calculated using the following relation:

% = 100 ( 1
)
Where Co is the starting concentration of the pollutant before adding the catalyst and Ct is the concentration of the pollutant after degradation at time t.

Antimicrobial activity

The disc diffusion method was recognized to test the antibacterial activity for Degussa, the biogenic AgNPs, and AgNPs/ Degussa nanocomposite against different human pathogenic microbes: S. aureus, E. coli, C. albicans, and A. niger. Nutrient agar medium plates were more suitable to cultivate bacteria and yeast, and a Czapek-Dox agar plate medium for fungal test microbe incubated at 37 °C for 24 hours. Each plate was seeded uniformly with 0.1 mL of (10 7 -10 8 ) cells/mL from bacterial and yeast test microbes, but for fungal (10 6 -10 7 ) cells/mL. Then one drop of melted agar was poured into a hand-made uniform hole with a diameter 1cm in the center of each plate. The plates were kept at temperature 4 o C for 4 hours to attain maximum diffusion. Then, the treated plates were incubated at 37 o C for one day for bacteria and at 30 o C for two days in the upright position to allow the optimal growth of the organisms.

Cell Culture evaluation

The cytocompatibility of the fabricated AgNPs and AgNPs/Degussa nanocomposite were investigated using human cell line PC3 (Prostate carcinoma) and Hela (Epitheliod carcinoma).

Before seeding, the samples were diluted according to the serial concentrations from 200 to 3.125 µg/mL, followed by soaking in absolute ethanol for 15 min and sterilization under UV light for an hour and then soaked in phosphate-buffered saline (PBS) thrice for further complete purification.

Briefly, PC3 and Hela were seeded into 96 well plates and cultured in an incubator (humidified with 5% CO2 balanced air) at 37 o C for one day. Then the selected cells were seeded with a specific density of 5x10 3 cells/cm 2 onto the sterilized nanoparticles. After 5 days incubation, the media was removed and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide) was injected into each well. 150 µL of Kit-8, CCK-8 solution was used to count the cell viability on tested nanoparticle concentrations. Cell viability is defined as the percentage of viable cells to the total cell number and expressed as follows.

Viability % = Mean optical density of test samples Mean optical density of the control ×100 n = 5 2

Results and discussion

Phytochemical assessment

Active phytochemical components are depicted in Table1. In this protocol, Banana Waste Peduncles pure extract exhibited positive outcomes towards alkaloids, glycosides tannins, steroids, phenols, anthraquinone, and flavonoids. The presence of such strongest constituent has antioxidant activity and are able to reduce Ag + to Ag 0 . Otherwise, these contents perform capping and stabilizing agent as well owing to the reduction affinity accompanied with the electron-donating capability of such as phenol hydroxyl. So, the structure of phenolic hydroxyl groups, position, and chemical number are primarily responsible for preserving and reducing ability. Likewise, similar findings discussed the total quantitative and qualitative phenolic and flavonoid in various extracts which used for the green synthesis of metallic nanoparticles [START_REF] Asghar | Green synthesized and characterized copper nanoparticles using various new plants extracts aggravate microbial cell membrane damage after interaction with lipopolysaccharide[END_REF][START_REF] Rajaram | Green synthesis of silver nanoparticle using Tephrosia tinctoria and its antidiabetic activity[END_REF][START_REF] Mariselvam | Green synthesis of silver nanoparticles from the extract of the inflorescence of Cocos nucifera (Family: Arecaceae) for enhanced antibacterial activity[END_REF].

HPLC examination

According to the HPLC analysis, Banana Waste Peduncles pure extract was included gallic acid, catechin, chlorogenic acid, caffeic acid, rutin, ellagic acid, quercetin, and kaempferol (Fig. 1 & Table 2). As validated in literature these components are able to be applied in therapeutic applications. and AgNPs/Degussa nanocomposite under normal conditions are shown in Fig. 2. The strong peak from 250 to 350 nm reveals the presence of the Ti-skeleton of the biphasic P25 [START_REF] Nalajala | Why the thin film form of a photocatalyst is better than the particulate form for direct solar-to-hydrogen conversion: a poor man's approach[END_REF].

Indeed, the UV-visible spectrum confirmed the formation of plasmon AgNPs and showed a typical resonance of the silver surface plasmon at a wavelength of approximately 421 nm due to the collective oscillations of free electrons located at the surface of metallic nanoparticulate [START_REF] Kodom | Silver nanoparticles influence on photocatalytic activity of hybrid materials based on TiO2 P25[END_REF].

These fluctuations are determined by the particle size, which then determines a specific absorption wavelength range in the visible spectrum. The presence of a single-surface plasmon resonance peak in the absorption spectrum of the green prepared AgNPs so far determines its spherical shape [START_REF] Paul | Role of surface plasmons and hot electrons on the multi-step photocatalytic decay by defect enriched Ag@ TiO2 nanorods under visible light[END_REF]. Furthermore, numerous other reports have confirmed that the resonance peak of AgNPs colloidal solutions occurs in this region [START_REF] Jebril | Green synthesis of silver nanoparticles using Melia azedarach leaf extract and their antifungal activities: In vitro and in vivo[END_REF]. Otherwise, there is a redshift in the wavelength value of the maximum absorption band during the interaction between AgNPs and P25 which is explained based on increasing in particle size [START_REF] Wang | Nanogold plasmonic photocatalysis for organic synthesis and clean energy conversion[END_REF]. The FTIR spectral analyses were performed for BWP extract, AgNPs, and AgNPs/Degussa nanocomposite. In Fig. 3 the FTIR spectrum of the BWP extract sample showed an absorption peak at 3453 cm -1 corresponds to O-H stretching vibration that belongs to polyphenols [START_REF] Agnihotri | Photocatalytic and antibacterial potential of silver nanoparticles derived from pineapple waste: process optimization and modeling kinetics for dye removal[END_REF]. The broad peak displayed at 2102 cm -1 , intense peak at 1642 cm -1 , small sharp peak at 1302 cm -1 could be attributed to C≡C stretching vibrations alkynes, C=C stretching vibrations of the structure of aromatic rings in the polyphenols, and C-O-C stretching vibration of carboxylic groups, respectively. The observed result confirms the structure of the BWP extract (Fig. 4a) [START_REF] Awad | Green synthesis of gold nanoparticles: Preparation, characterization, cytotoxicity, and anti-bacterial activities[END_REF]. The FTIR spectra of AgNPs exhibited several peaks, as AgNPs fingerprint is ascribed for the band appears at 823 cm -1 (Fig. 4b) [START_REF] Chen | N-doped mesoporous TiO2 nanoparticles synthesized by using biological renewable nanocrystalline cellulose as template for the degradation of pollutants under visible and sun light[END_REF]. The observed peaks at 1633 cm -1 and 1367 cm -1 are due to N-H amines and aliphatic C-H respectively. The structure of the resulting AgNPs/Degussa nanocomposite was confirmed by the presence of a peak at 653 cm -1 ascribed to the bending vibration mode of the O-H group and Ti-O-Ti bridging stretching mode [START_REF] An | Nano-fibrillated cellulose (NFC) as versatile carriers of TiO2 nanoparticles (TNPs) for photocatalytic hydrogen generation[END_REF](Fig. 4c). The water adsorbed onto the surface of AgNPs was confirmed by the presence of a peak at 1610-1650 cm -1 corresponds to the -OH bending vibration mode of water [START_REF] Atarod | Euphorbia heterophylla leaf extract mediated green synthesis of Ag/TiO2 nanocomposite and investigation of its excellent catalytic activity for reduction of variety of dyes in water[END_REF].

The morphology and size of the Degussa, the biosynthesized AgNPs, and AgNPs / Degussa nanocomposite was studied using TEM (Fig. 5). As shown in Fig. 5a,b TEM images of two different magnification of P25 that exhibited the aggregated spherical shape with an average size of ~ 25 nm, which revealed two phases of material consisting of (anatase-TiO2 and rutile one).

Fig. 5c illustrates the HR-TEM lattice space of anatase facet (101) and rutile facet (110) which is almost identical to the polycrystalline SAED pattern (Fig. 5c) [START_REF] Chen | N-doped mesoporous TiO2 nanoparticles synthesized by using biological renewable nanocrystalline cellulose as template for the degradation of pollutants under visible and sun light[END_REF][START_REF] Han | Degussa P25 TiO2 modified with H2O2 under microwave treatment to enhance photocatalytic properties[END_REF].

From Fig. 5d, it was observed that AgNPs having spherical shape as well as monodisperse near hexagonal shapes with approximately average size 15-20±2.3 nm. HR-TEM photograph are depicted in Fig 5e,f, which proved high crystalline nature of green prepared AgNPs by the presence of lattice constant with a distance of 0.23nm which agree with lattice fringe that recorded in some reported elsewhere for further support our claim system [START_REF] Ali | Synthesis and characterization of phytochemical fabricated zinc oxide nanoparticles with enhanced antibacterial and catalytic applications[END_REF][START_REF] Gavamukulya | Green synthesis and characterization of highly stable silver nanoparticles from ethanolic extracts of fruits of Annona muricata[END_REF][START_REF] Gul | Grass-mediated biogenic synthesis of silver nanoparticles and their drug delivery evaluation: A biocompatible anti-cancer therapy[END_REF][START_REF] Some | Bio-molecule functionalized rapid one-pot green synthesis of silver nanoparticles and their efficacy toward the multidrug resistant (MDR) gut bacteria of silkworms (Bombyx mori)[END_REF][START_REF] Qin | Photocatalysts fabricated by depositing plasmonic Ag nanoparticles on carbon quantum dots/graphitic carbon nitride for broad spectrum photocatalytic hydrogen generation[END_REF].

Fig. 5g,h&i represent different magnifications of AgNPs/Degussa nanocomposite, which exhibited reduced crystallinity shape, compared with pure P25 or AgNPs. Presumably, this is attributed to the presence of more crowded oxygen atoms on the surface of TiO2 crystal lattice [START_REF] Khan | Fabrication of TiO2/Ag/Ag2O nanoparticles to enhance the photocatalytic activity of Degussa P25 titania[END_REF]. Otherwise, HR-TEM revealed that successful interaction between AgNPs and P25 and good dispersion of P25 within the cluster of AgNPs. Consequently, the crystallinity was randomly reduced and smoothly surrounded AgNPs with rapid, homogenous growth of P25.

Fig. 6 shows SEM surface texture and EDX analysis of AgNPs and AgNPs/Degussa nanocomposite. It was observed that AgNPs are distributed in the form of soft coral-like structure with aggregated in small sizes in different areas (Fig. 6a). This is probably attributed to the formation of hydrogen bonds with BWP bio-components [START_REF] Vijilvani | Antimicrobial and catalytic activities of biosynthesized gold, silver and palladium nanoparticles from Solanum nigurum leaves[END_REF]. Besides, the good distribution with a small size of AgNPs could be attributed to BWP bio-components which act as both reductants for Ag ions and at the same time as a stabilizing agent for the produced AgNPs [START_REF] Doan | Utilizing waste corn-cob in biosynthesis of noble metallic nanoparticles for antibacterial effect and catalytic degradation of contaminants[END_REF].

Consequently, the synthesized AgNPs/Degussa has a morphological feature (Fig. 6b) which differs from that of AgNPs alone. The difference is the enlargement of particle size up to 25±5 nm rather than 14.1 ±3 nm of pristine AgNPs (from XRD analysis) which could be ascribed to the combination of two components [START_REF] Dong | Plasmon enhanced photocatalytic and antimicrobial activities of Ag-TiO2 nanocomposites under visible light irradiation prepared by DBD cold plasma treatment[END_REF][START_REF] Wodka | Photocatalytic activity of titanium dioxide modified by silver nanoparticles[END_REF].

The EDS signals and mapping techniques of AgNPs/Degussa nanocomposite are presented in Fig. 6c, which demonstrated the presence of the following elements: Ti, C, N, and O, as well as Ag with the percentage of major Ag (52.36%) and minor Ti (8.91%). The peaks of oxygen, and carbon were observed mainly due to the bioactive metabolite's components of the BWP aqueous extract that are responsible for the reduction operation and capping of NPs.

3.4.Photocatalytic activity of AgNPs, AgNPs/Degussa

Photocatalytic degradation of MB

The photocatalytic degradation of prepared AgNPs and AgNPs/Degussa nanocomposite towards MB was studied under visible irradiation (Fig. 7). All AgNPs/Degussa nanocatalyst produced better degradation of MB under dark and light conditions, which may be due to the synergistic effect of AgNPs and P25 [START_REF] Singh | Synthesis of Ag-TiO2 hybrid nanoparticles with enhanced photocatalytic activity by a facile wet chemical method[END_REF][START_REF] Chen | Green synthesis of Ag-TiO2 supported on porous glass with enhanced photocatalytic performance for oxidative desulfurization and removal of dyes under visible light[END_REF]. As shown in Fig. 7a is the apparent pseudo-First-order rate constant (Fig. 8a,b). The values of rate constants are 0.0121 min -1 and 0.0254 min -1 for AgNPs and P25 respectively. In the case of AgNPs/P25 nanocatalyst, the rate constant reading is 2.09-fold stronger than pure P25

suggesting that AgNPs/Degussa has superior photocatalytic efficiency for the degradation of a large fraction of MB.

The reusability of any catalytic nanomaterials is strongly related to its stability to be used in continuous practical applications. After optimal degradation was attained, AgNPs and AgNPs/Degussa were collected using centrifugation, washed, dried, and subjected to several reusability degradations (eight cycles). As shown in Fig. 8c,d, the prepared nanocatalyst still maintains high good property with tiny loss of degradation even after eight cycles, indicating that the green prepared AgNPs and combinational form AgNPs/Degussa have excellent photochemical stability.

Catalytic reduction of Cr(VI)

The photocatalytic reduction of aqueous Cr(VI) onto AgNPs and AgNPs/Degussa was performed at R.T. UV absorbance spectral change is an indicator of the reduction property.

Generally, the main absorption peak of the photoreduction of Cr(VI) was monitored by the decay around 350 nm. As obtained from Fig. 9, different reduction states were obtained. In Fig. 9a, one hour is taken to decay only 9% Cr(VI) under visible-light irradiation. Fig. 9b, nearly the same percentage of reduction takes place in the present very low concentration radical from an electron donor such as citric acid, affirming that Cr(VI) is stable in light and absence of the prepared nanocatalyst.

The scenario was changed in the presence of AgNPs and AgNPs/Degussa as well as these photocatalysts keeping their progress towards quick destruction of highly toxic Cr(VI) to safer Cr(III). As illustrated in Fig. 9c, d and under identical experiment, the reduction process only takes 24 min and 16 min by AgNPs and AgNPs/Degussa nanocatalyst respectively, which demonstrated the synergistic role of the aforementioned photocatalysts, is valid comparing with other kinds of photocatalysts that reported in other works and summarized in Table .2.

Proposed mechanistic approach

The photocatalytic redox mechanism for MB and Cr(VI) by AgNPs and AgNPs / Degussa nanocomposite was examined. It is assumed that the Schottky junction occurs between Ag and P25 when they are very close to each other. Since the Fermi level of P25 is very high compared to Ag [START_REF] Kusiak-Nejman | Photocatalytic oxidation of nitric oxide over AgNPs/TiO2loaded carbon fiber cloths[END_REF] and, therefore, electrons cannot exceed this level in pristine P25.

The establishment of the Schottky barrier complicates the transfer of electrons from Ag to P25. However, there is still no detailed scientific mechanism to explain such an electron transport system [START_REF] Dong | Plasmon enhanced photocatalytic and antimicrobial activities of Ag-TiO2 nanocomposites under visible light irradiation prepared by DBD cold plasma treatment[END_REF][START_REF] Wen | Preparation and visible light photocatalytic activity of Ag/TiO2/graphene nanocomposite[END_REF]. The probable reason suggests that the collective vibrations of electrons to excite the surface plasmon can lead to excitation between the bands, giving the electrons moving at the interface sufficient energy to overcome the Schottky barrier by overcoming the Schottky barrier in AgNPs/P25 [START_REF] Wang | Gas-exfoliation assisted fabrication of porous graphene nanosheets derived from plumeria rubra for highly efficient photocatalytic hydrogen evolution[END_REF]. Once excitation by visible light, the energized electrons are excited to the CB of P25, and accordingly, electron/ hole are generated on the photoactive surface [START_REF] Ahmed | Efficient photocatalytic degradation of toxic Alizarin yellow R dye from industrial wastewater using biosynthesized Fe nanoparticle and study of factors affecting the degradation rate[END_REF].

The (h + ) in the V.B of P25 acting as a powerful oxidant that can react directly with contaminants or react with H2O molecules in a solution produced by H + and . OH, radicals, which rapidly degrading MB to the popular H2O & CO2. At the same time, oxidized Ag atoms absorb electrons from the water or MB molecules which are adsorbed on the P25 surface and are regenerated. The reaction of Ag ions with H2O molecules or hydroxide ions creates hydroxyl radicals (˙OH). These reactive oxygen species (˙O˙2 and ˙OH), are very powerful oxidizing agents for the degradation of cationic MB Which promotes the photocatalytic reduction of Cr(IV) to Cr(III) [START_REF] Shoueir | Tailoring the surface reactivity of plasmonic Au@ TiO2 photocatalyst bio-based chitosan fiber towards cleaner of harmful water pollutants under visible-light irradiation[END_REF][START_REF] Ahmed | Efficient photocatalytic degradation of toxic Alizarin yellow R dye from industrial wastewater using biosynthesized Fe nanoparticle and study of factors affecting the degradation rate[END_REF]. Therefore, O2 ·¯ able to interact with H2O forming · OOH radicals, followed by subsequent into H2O2. Alternatively, the reaction between H2O and O2 ·¯ under solar irradiation results in ·OH. As a result, the holes and electrons generated can also be fully involved in the photocatalytic reactions and strong photocatalytic activity is expected. The possible major photocatalytic degradation steps can be summarized as follows: The observed results showed that Degussa (P25) did not provide any noticeable antimicrobial activities against the tested microbes, suggesting that Degussa (P25) is completely attacked by the microbes, thus, the inhibition zone is zero (Fig. 10a). The antimicrobial properties of AgNPs have been carried out using two different concentrations: 5 mg/l and 10 mg/l. As can be seen from Fig. 10b, c 5 mg/l AgNPs are more efficient for killing and inhibiting the diffusion of the tested microbes compared with those with higher concentration. Similar behavior was also observed by high concentration (10 mg/l) [START_REF] Vijilvani | Antimicrobial and catalytic activities of biosynthesized gold, silver and palladium nanoparticles from Solanum nigurum leaves[END_REF][START_REF] Shoueir | Encapsulation of extremely stable polyaniline onto Bio-MOF: Photoactivated antibacterial and depletion of ciprofloxacin from aqueous solutions[END_REF]. However, AgNPs/Degussa nanocomposite enhanced effect in killing the microbes than controlled AgNPs (Fig. 10d). It was also observed that S. aureus, C. albicans, A. niger are less resistant to the nanocomposite and AgNPs when compared to E. Coli. Based on these results, it can be concluded that AgNPs have a significant role in improving the antibacterial activity of the nanocomposite.

The antimicrobial effect of the fabricated AgNPs or AgNPs/Degussa nanocomposite takes two stages. Firstly, the polyphenols present in BWP extract is supposed to bind with the protein present in the microbe [START_REF] Ali | Synthesis and characterization of phytochemical fabricated zinc oxide nanoparticles with enhanced antibacterial and catalytic applications[END_REF]. Thus, it changes the membrane potential and decreases the adenosine triphosphate synthase activities, consequently, the metabolism process is reduced.

Secondly, the biological system fails as the ribosome for tRNA binding declines. The capping agent's binding properties enable the penetration of biogenic AgNPs or AgNPs / Degussa into the inner core of microbial cells [START_REF] Vijilvani | Antimicrobial and catalytic activities of biosynthesized gold, silver and palladium nanoparticles from Solanum nigurum leaves[END_REF]. They exhibited a less toxic effect on mammalian cells at the same time, as shown in Fig. 10e. Besides, referring to their smaller size, AgNPs have a larger surface area and therefore will provide more surface reactive sites for efficient penetration ability, allows them to interact closely with microorganisms.

In this protocol, BWP extract was used as a powerful reducing and capping agent to obtain AgNPs as well as a strong protein binder. Therefore, this extract plays a role in enhancing the antimicrobial activity of AgNPs as well. It has been reported that the antimicrobial activity of any metal depends on the degree of reduction and capping [START_REF] El-Shafai | Fabrication and characterization of graphene oxide-titanium dioxide nanocomposite for degradation of some toxic insecticides[END_REF]. Also, the effective antibacterial agent should not only be toxic to numerous pathogenic bacteria but should also have properties that allow it to be coated as an antibacterial coating on various surfaces such as medical applications, purifying testing, and food packing, etc.

3.6.Cytotoxicity evaluation

The cytotoxicity assessment studies were tested on Hela (Epitheliod Carcinoma) and PC3

(Prostate Carcinoma) according to the method MTT assay protocol that was documented elsewhere [START_REF] Gavamukulya | In search of new anticancer drugs: Data for cytotoxic activities of green synthesized silver nanoparticles from ethanolic extracts of fruits and leaves of Annona muricata and 5-Fluorouracil against HeLa, PC3 and PNT1A cell lines[END_REF]. Fig. 11 showed the effect of green synthesized AgNPs and AgNPs / Degussa with different concentrations (200-3.125 µg/ml) for 24 h onto Hela and PC3 cell growth. The cytocompatibility of the nanoparticles depends on the various parameters such as nanoparticles' size, concentration, charge, shape, and chemical surface composition [START_REF] Aslany | Characterization and Evaluation of Cytotoxic and Apoptotic Effects of Green Synthesis of Silver Nanoparticles Using Artemisia Ciniformis on Human Gastric Adenocarcinoma[END_REF].

AgNPs and AgNPs/Degussa were applied on two different cancer cells and the cell viability was depicted in Fig. 11. The percentage of death between cancer cells increased concerning the rise in the concentration of nanoparticles. According to AgNPs, induced over 92.42% of Hela cells (IC50 12.23 g/ml) and eradicated nearly 85.45% of PC3 cells (IC50 43.46 g/ml) at a working concentration 200 g/ml as shown in Fig. 11a,b. On the other side, AgNPs/Degussa nanocomposite at higher concentration 200 g/ml inhibited over 94.85% of Hela cells (IC50 11.12 g/ml) and 86.77% of PC3 cells, (IC50 33.83 g/ml) as observed in Fig. 11c,d.

At concentration 3.15 g/ml, the cell viability attained 100% revealing that AgNPs and AgNPs/ Degussa are compatible nanostructured and exerted higher cytocompatibility and nontoxicity with relative cell viabilities. In the literature, more than 85 % of cell-viability exhibited effective biosystem and classified as cytocompatible [START_REF] Guan | Efficient and robust Cu/TiO2 nanorod photocatalysts for simultaneous removal of Cr (VI) and methylene blue under solar light[END_REF][START_REF] Abdelbar | Highly ordered functionalized mesoporous silicate nanoparticles reinforced poly (lactic acid) gatekeeper surface for infection treatment[END_REF].

Conclusions

Herein, we report the photocatalytic decontamination of MB textile dye and Cr(IV) as common and hazardous pollutants under irradiation of visible light by using green synthesized AgNPs and AgNPs/Degussa hybrid nanomaterials. This photocatalytic system is economical, environmentally friendly, and can be used in the industrial application of water purification by using solar light owing to their photochemical stability. The photocatalytic performance was gradually increased by the presence of combinational AgNPs and Degussa. As a result, full degradation of MB and complete reduction of Cr(VI) within minutes. Moreover, the nanocomposite exhibited a significant antibacterial ability against different microbes (G+ ev) more than (G-ev), as well as higher cytocompatibility and non-toxicity with relative cell viabilities. In turn, the bioactive components of BWP extract played a critical role in enhancing the antibacterial and cytotoxicity performance of AgNPs.

Fig. 3 3

 33 Fig.3shows the XRD pattern of the samples to affirm the structure, phase, and crystallinity.For Degussa, the diffraction peaks obtained at 2θ = 25.1 o , 38.4 o , and 48.3 o which correspond to the planes coinciding with the (101), (004), and (200) of the bicrystalline structure, which can be assigned to the anatase phase, (JCPDS card no. 21-1276)[START_REF] Hossain | A comparative study on the influence of pure anatase and Degussa-P25 TiO2 nanomaterials on the structural and optical properties of dye sensitized solar cell (DSSC) photoanode[END_REF]. The diffraction peaks of the distinct lattice planes agree with the rutile phase (JCPDS card no. 21-1272) occur at the exhibited position; 27.5⁰, 36.4⁰, and 41.7⁰ of the crystalline planes (110), (101), and (111)[START_REF] Chen | Multi-functional integration of pore P25@ C@ MoS2 core-double shell nanostructures as robust ternary anodes with enhanced lithium storage properties[END_REF].As can be seen from Fig.2, the observed well-resolved diffraction peaks in XRD of AgNPs located at 2θ = 27.1⁰, 31.9⁰, 46.3⁰, 54.7⁰, 57.3⁰, 67.5⁰, and 76.8⁰ corresponding to (220), (122), (231), (331), (241), (104), and (311) planes, confirming the presence of face-centered metallic AgNPs (JCPDS card no. 04-0783) as agreed with published elsewhere[START_REF] Chen | Enhanced antimicrobial efficacy of thermal-reduced silver nanoparticles supported by titanium dioxide[END_REF]. The tiny extreme peak of metallic silver at 38.1 o overlaps with the crystalline planes (004) of anatase after P25 decorated AgNPs and obscured their presence. Besides, the Ag / Degussa heterostructure exhibit a slight peak at position 35.48 o , which also showed the P25 involved and interacted with the Ag surface[START_REF] Wang | One-pot solvothermal synthesis of carbon dots/Ag nanoparticles/TiO2 nanocomposites with enhanced photocatalytic performance[END_REF].

  , b the adsorption characteristic in the dark condition of AgNPs and AgNPs/Degussa is 70% within 20 min and 72.4% within 12 min, respectively. Complete degradation of MB under visible light was achieved with the combination of AgNPs / Degussa. The intensity of the absorption peaks of M.B at ~ 664 and 292 nm gradually decreased with irradiation time until it diminished. It was noticeable that hypochromic shifts of the absorbance peak were not observed without any intermediate as shown in Fig. 7c, d. The decomposition results of MB were suited with the Firstorder-kinetic equation model: ln / = -1 233 t, where 4 regarded to degradation time at time 4 and 1 233

Fig. 10 detects

 10 Fig. 10 detects the antimicrobial properties, and the calculated diameter of the inhibition zone is diagrammatical of the Degussa, AgNPs, and AgNPs/Degussa respectively. The evaluation was carried out on different species of microbes as Staphylococcus aureus ATCC 6538 (G+ve), Escherichia coli ATCC 25922 (G-ve), Candida albicans ATCC 10231 (yeast), and Aspergillus niger NRRL A-326 (fungus).

Fig. 1 Fig. 2

 12 Fig. 1 (a) HPLC chromatogram and (b) chemical structures of some selected polyphenolic compounds in BWP extract.

Fig. 3 Fig. 4 FTIR

 34 Fig. 3 XRD pattern of (a) Degussa (P25), (b) green synthesized AgNPs, and (c) AgNPs/Degussa nanocomposite.

Fig. 5 Fig. 6

 56 Fig. 5 TEM images of (a, b) P25 at two different magnification, (c) SAED pattern of P25, (d) green fabricated AgNPs (inset SAED), (e,f) HR-TEM of prepared AgNPs, (g,h&i) TEM images of AgNPs/Degussa nanocomposite at 50, 20nm and 5 nm scale bar respectively.

Fig. 7 Fig. 8 Fig. 9

 789 Fig. 7 UV-absorbance of M.B (a) green prepared AgNPs in dark, (b) adsorption by AgNPs/Degussa nanocatalyst in dark condition, (c) UV-absorbance of AgNPs under light irradiation, and (d) degradation of Ag/Degussa nanocatalyst by visible-light at controlled pH = 7 and room temperature).

Table 1 .

 1 Existence of the phytochemical active components in the waste extract.

	Phytochemical test type	Result Intensity
	Alkaloids	+++	High
	Glycosides	-	NA
	Tannins	+	Law
	Steroids	+	Law
	Phenols	+++	High
	Anthraquinone	-	NA
	Flavonoids	++	Moderate

Table 2 .

 2 Total phenolic and flavonoid content in BWP.

Active component Conc. (mg of GAE/g DW)

	3.3.Structural studies
	UV-Vis spectral investigation of the colloidal form containing B.W.P, AgNPs, Degussa,
	gallic acid	5.667
	Catechin	16.603
	chlorogenic acid	18.502
	caffeic acid	20.015
	Rutin	32.607
	ellagic acid	33.412
	Quercetin	40.266
	Kaempferol	44.651

Table 3 .

 3 Comparison of photocatalytic decomposition and photoreduction performance ofAgNPs and AgNPs/Degussa with different kinds of photocatalysts ascribed in the literature.

	Photocatalyst	Pollutant,	Photocatalyst	Degradation	Light source with	References
		Concentration	amount	time (min)	(Intensity)
	Ag-TiO2 nanowires	M.B ,	30 mg	80	Sunlight	[72]
		10ppm	0.5 g/L
	Ag-TiO2	M.B ,	8 mg	200	Hg Lamp	[73]
	nonohybrids	61.5 mg/L			(125W)
	Ag/TiO2	M.B ,	5 mg	80	Halogen	[74]
		10 Mg/L			Lamp (300W)
	AgNPs/Degussa	M.B , 7 ppm	5 mg	50	Tungsten Lamp (150W)	Present work
	AgNPs green bio-	M.B ,	5 mg	65	Tungsten Lamp	Present
	fabricated	7ppm			(150W)	work
	TiO2@Pt@CeO2	Cr(IV) ,	30 mg	120	Xenon Short Arc	[75]
		100 mg/L			Lamp (300W)
	Ag/TiO2/CoFe2O4	Cr(IV),	5 mg	300	Visible Lamps	[76]
		5 mg/L			(240W)
	AgNPs/Degussa	Cr(IV) , 10 mg/L	5 mg	16	Tungsten Lamp (150W)	Present work
	AgNPs green bio-fabricated	Cr(IV) , 10 mg/L	5 mg	24	Tungsten Lamp (150W)	Present work
	3.5. Antibacterial experiment