Synthesis of silver nanoparticles formed by Chaerophyllum macrospermum and Eremurus spectabilis biomaterial and investigation of photovoltaic parameters by adding silicon phthalocyanine

Abstract Silver nanoparticles (AgNPs) were obtained by green synthesis using Chaerophyllum macrospermum (CM) and Eremurus spectabilis (ES). These particles were characterized by TEM, XRD, IR, UV, mass, and NMR spectra. TEM images show that the mean particle size of CM-AgNPs was 30 nm and the diameter of ES-AgNPs was 14.2 nm. XRD measurements showed that CM-AgNPs were 30.85 nm and ES-AgNPs 18.80 nm in a perfect face-centered cubic crystal structure. CM-AgNP showed maximum absorption at 453 nm and ES-AgNP at 455 nm; AgNPs exhibited a strong surface plasmon resonance (SPR) and played a role in stabilization. A silicon phthalocyanine compound was synthesized and characterized. The photovoltaic properties of the axial phthalocyanine compound with and without doping of Chaerophyllum macrospermum and Eremurus spectabilis silver nanoparticles were investigated. Better dye-sensitive solar cells were formed by doping silver nanoparticles to phthalocyanine compounds with an increase in the percentage of energy conversion efficiency by 0.26 with ESAgNP doping and 0.76 with CMAgNP doping. Graphical abstract


Introduction
Generating energy through photovoltaic cells from the sun is widely used.The sun has such enormous energy that the energy, which hits the earth's surface in 1 h, could meet all the needs of the world for a year.Ways to obtain such environmentally friendly energy both at an affordable cost and at an adequate level are being investigated.Although solar cells are used to obtain energy in many areas of our lives, they are not sufficient.There is high demand for development of inexpensive and cost-effective ways for widespread use of photovoltaic batteries in the renewable energy market.Solar cells, which have a working principle similar to photosynthesis in Nature, transmit the light to the dye material by allowing it to pass through the glass surface with high optical transmittance.Dyes also absorb incoming rays and excite electrons through photons.These excited electrons pass to an upper band and move to the opposite electrode in the photovoltaic cells (PV).The dye molecule completes one cycle of the system by taking electrons from the electrolyte to regain the lost electron [1,2].
Depending on nano-technological developments, synthesis and usage of silver nanoparticles are increasing.The choice of green synthesis, which is more environmentally friendly and economical, attracts the attention of researchers.The synthesis of silver nanoparticles by green synthesis is becoming increasingly common [3,4].Silver has many uses due to its good conductivity and antimicrobial properties.The literature describes syntheses and use of silver nanoparticles for different purposes [5].Chaerophyllum macrospermum and Eremurus spectabilis plants are consumed locally as food.In addition, these plants show antibacterial and antioxidant properties [6,7].Chaerophyllum macrospermum and Eremurus spectabilis silver nanoparticles can add to phthalocyanines investigated for dye-sensitized solar cells in this study.
Phthalocyanines are macrocyclic compounds with many applications [8].Phthalocyanine compounds are generally derivatized in the phthalocyanine ring peripherally, non-peripherally, or axially with different substituted groups.Thus, changes can occur in the chemical and physical features of the phthalocyanine compound formed [9].Numerous phthalocyanine compounds have been synthesized and extensively investigated for use in applications such as nonlinear optics [10,11], catalysts [12,13], dye-sensitized solar cells [14,15], photochromic material-making [16], ink [17], pigment [18], sensor [19,20], and a photosensitizer for photodynamic therapy [21,22].Phthalocyanines are also seen as promising antioxidant and antibacterial materials [23,24].In this context, use in antibacterial paint and textile industry draws attention as both an environmentally friendly and healthy method.Another notable type of research from the extensive uses of phthalocyanines is their interest in organic-inorganic hybrid perovskite solar cells [25,26].
Photonics, the science and technology that uses light, attracts researchers for the discovery of new photonic properties and the development of technologies with new compounds and products [27].Materials to be used in photonics have found great success as waveguides.Ground-activated waveguides constitute a potentially important system to act as an effective optical medium for light dispersal and luminescence amplification [28]; there are specific systems used to increase the effectiveness of solar cells [29,30].The strategy is to use light shedding to improve the optical density of solar cells by reducing the thickness of the absorber layer [31].This lowers the material budget value and improves the mechanical flexibility of devices in applications while also making photovoltaic properties efficient [32].Both the back surfaces and the front surfaces are very important to increase the length of the optical path inside the absorber layer and scattering light [33].Application in very efficient Si cells has yielded superior efficiency in those achieved with optimized periodic texturing [34].The photo response of semi-metal complexes and the way they are affected by the environment can be predicted [35].
In this study, a phthalocyanine compound carrying bis(3-chloropropanoate) substituent axially, Chaerophyllum macrospermum, and Eremurus spectabilis silver nanoparticles were synthesized and characterized.Photovoltaic effect was investigated by doping Chaerophyllum macrospermum and Eremurus spectabilis silver nanoparticles with phthalocyanine.

Materials and characterization
Chaerophyllum macrospermum (Willd.ex Sprengel) and Eremurus spectabilis plants were collected separately.The plants were washed with tap water followed by deionized water and then dried in a shaded area.These dried plants were cut into small particles and preserved for extraction.Silver nitrate, chloroform (CHCl 3 ), tetrahydrofuran (THF), dichloromethane (CH 2 Cl 2 ), toluene, and 3-chloropropionic acid were purchased from Sigma, Alfa Aesar, Acros, and Merck.The structures were analyzed by a Thermo Scientific FT-IR spectrophotometer, and a PANalytical Empyrean XRD was used for qualitative identification of nanoparticles (Atat€ urk University, Turkey).The transmission electron microscopy (TEM) analysis grid was taken at the University of Atat€ urk, Turkey.Hitachi U-2900 spectrophotometer, Agilent 400 MHz spectrometer, and LC-MS electrospray ionization technique were used for electronic, NMR, and mass spectral data, respectively.

Preparation of plant extracts and silver nanoparticles
Extracts of the first leaves and stems of Chaerophyllum macrospermum and Eremurus spectabilis plants were used.Approximately 10 g of CM and ES were added to beakers containing 500 mL of deionized water.The beakers were heated by stirring at 80 C for 1 h.The resulting aqueous mixtures were filtered through Whatman No 1 filter paper and labeled as CM-extract and ES-extract.These extracts were stored in the refrigerator at 4 C for subsequent experiments.
To silver nitrate solution (1 mM), 5 mL of CM extract was added to 95 mL AgNO 3 solution and kept in the dark at room temperature.Similarly, 5 mL of ES extract was added to 95 mL of AgNO 3 solution and kept in the dark.Color changes in both mixtures began to be observed over time.Mixtures that were initially light yellow turned dark brown after 24 h.This color change means that Ag ions are reduced by plants, the reaction is completed and stabilization takes place.The mixtures of dark brown CM-AgNP and ES-AgNPs formed after 24 h were separated from the solid particles with the help of a centrifuge and Whatman No 1 filter paper.The solids were washed with deionized water and filtered again.The resulting solid AgNPs were dried, powdered, and preserved for characterization.

Photovoltaic study
Photovoltaic parameters of the samples were determined in accord with the studies in the literature [14,36].

Results and discussion
Bis(3-chloropropanoate)phthalocyaninato silicon(IV) was obtained from the reaction of SiPcCl 2 and 3-chloropropionic acid.Characterization of 3 was performed with 1 H and 13 C NMR, UV-Vis, mass, and FT-IR spectra.The synthesis route of the compound is given in Scheme 1.
In the 1 H NMR spectrum of 3 the aromatic protons in the phthalocyanine ring are observed at 9.71-7.26ppm.Aliphatic protons appear at 3.76 and 2.86 ppm (Figure S1).These data constitute appropriate data with the structure of 3. In the 13 C NMR spectrum of 3 in CDCl 3 , characteristic peaks were seen at 163.29-124.03ppm.Peaks of CH 2 were observed at 37.01 ppm.
When the FT-IR spectrum is examined, the aromatic C-H vibration is at 3064 cm À1 and the aliphatic CH 2 groups are at 2951, 2920, and 2850 cm À1 .The carbonyl peak in the compound is found at 1691 cm À1 .The vibrations of C ¼ C peaks are observed at 1529 cm À1 .The C-Cl vibration present in 3 is seen as a sharp peak at 731 cm À1 (Figure S2).The calculated mass of 3 and the mass obtained as a result of LC-MS analysis exactly match (Figure S3).
In UV-Vis spectra of 3 in THF, Q and B bands, characteristic specific to phthalocyanine, are observed at 680 and 355 nm, respectively, with a shoulder at 610 nm.The absorptions measured at different concentrations are given in Figure 1.Compound 3 exhibits non-aggregation behavior in the measurement range, obeying the Lambert-Beer law.It is important for applications that 3 does not clump together in the solvent  environment.This axial phthalocyanine compound shows good solubility in dichloromethane, chloroform, tetrahydrofuran, and toluene solvents.The absorption peaks of 3 in these solvents are given in Figure 2. The absorption, excitation, and emission spectra of 3 are given in Figure 3. Absorption at 680 nm, excitation at 680 nm, and emission peaks at 688 nm are observed in spectra of THF solution.The Stokes shift is 8 nm, in a range compatible with similar silicon phthalocyanine Stokes shifts.

Adsorption measurement of nanoparticles
UV-Vis spectroscopy should first be used to study the bioreduction of metal ions into metal nanoparticles.The transformation of the extracts with AgNO 3 from light yellow to dark brown occurred within 24 h at room temperature.We can also confirm nanoparticle formation with UV-Vis spectrometry.Graphs showing the maximum absorbance peaks of CM-AgNP and ES-AgNPs obtained from Chaerophyllum macrospermum  and Eremurus spectabilis plants used as capping agents are shown in Figures S4 and  S5.Looking at the graphs obtained at the fifth hour of SPR formation in both nanoparticles, it is understood from the maximum absorbance peaks (ES-AgNP: 455 nm, CM-AgNP: 453 nm) that stabilization occurs at the end of 24 h, that reduction from AgNO 3 to silver metal continues.These values are similar to previous findings [37,38].The absorbance values in the graphs are proof that Ag nanoparticles originate from the surface plasmon resonance (SPR) band, which is proof that AgNPs are formed.As a result of the interaction of free electrons in SPR, AgNPs with light, the complex structure proteins, amino acids, enzymes, polysaccharides, alkaloids, tannins, phenolic, saponin, terpenoids, and vitamins, which surround the nanoparticles, cause the electromagnetic field to be strengthened and thus lead to a collective excitation release [39].The reason for the color change in AgNPs is SPR.

FT-IR spectroscopy of nanoparticles
FT-IR measurements were performed to determine the functional groups that stabilize the silver nanoparticles and reduce the silver ions.Figure S6 shows FT-IR spectrum of CM-AgNP and Figure S7 shows the ES-AgNPs spectrum.The presence of CM and ES phytocomponents in both biosynthesized AgNPs can be seen from the analysis results.The peaks of 3525 cm À1 and 3483 cm À1 in CM-AgNP and 3525 cm À1 and 3502 cm À1 in ES-AgNP are associated with -OH stretching of hydroxyl groups, which is believed to be an important contributing factor in the reduction of metal ions to metal nanoparticles (MNPs).The presence of peaks at 3118 cm À1 and 3099 cm À1 in CM-AgNPs indicates the presence of moderate C-H bonds.While not very sharp in CM-AgNPs (2987 cm À1 and 2881 cm À1 ), similar but sharper peaks at 2987 cm À1 and 2902 cm À1 in ES-AgNPs indicate strong C-H bonds.The peaks in CM-AgNP at 2380 cm À1 and 2312 cm À1 and the ES-AgNP peak at 2310 cm À1 result from CO 2 , and CN triple bond stretches in response to O ¼ C¼O stretching of flavonoids [40].The many strong vibrations with varying intensity between 1800 cm À1 and 1600 cm À1 seen in both nanoparticles belong to C ¼ O group vibrations.The 1519 cm À1 peaks in CM-AgNP and 1535 cm À1 in ES-AgNP contain the C ¼ C double-bond.In both AgNPs, as can be seen in the fingerprint region between 1550 cm À1 and 650 cm À1 , there are many C-O bonds of phytochemicals such as nitro compounds, alcohols, and esters, which cause strong vibrations.

Detection of morphological features with TEM
The morphological properties of synthesized silver nanoparticles were monitored using TEM. Figure 4 shows the TEM micrograph and average particle sizes of CM-AgNPs and Figure 5 shows the ES-AgNPs.
The homogeneous size distribution of CM-AgNP and ES-AgNPs prepared by using extracts of Chaerophyllum macrospermum and Eramurus Spectabilis as reducing agents were confirmed by TEM analysis.TEM micrographs clearly show that the phytochemicals in Chaerophyllum macrospermum and Eramurus Spectabilis cover and surround the silver atoms (Figures 4 and 5).The size distribution and shapes of the NPs were homogeneous and most of them had hemispherical shapes, indicating that the extract was efficiently sealed by its constituent biomolecules, preventing aggregation.The average size of the synthesized nanoparticles was 30 nm for CM-AgNPs and 14.21 nm for ES-AgNPs as a result of the analysis made with the ImageJ program.The TEM images show that the nanoparticles have a spherical structure.Studies confirming this have also been recorded [41].
Although large differences in size were observed in the morphological distributions of these two AgNPs via TEM images, the histogram graph taken from the TEM image showed that the particle size distributions of biosynthesized silver nanoparticles in both nanoparticles were close to each other and in the range of 10-20 nm.
In another study, the average size in the synthesis of green silver nanoparticles is in the range of 49.87-75.29 nm [5].Compared to these results, the average size range of 14.2-30.0nm obtained in this study is smaller, increasing the surface area.

XRD analysis
Representative XRD models for synthesized nanoparticles are presented in Figure 6.The peaks at 2h of 38.0 , 44.Smaller crystal sizes in nanoparticles, especially in ES-AgNP, that is, below 20 nm, increase the importance of the material [43].
The other 2h peaks in both XRD plots are due to the presence of active phytochemicals such as saponins, flavonoids, alkaloids, tannins in the aqueous extract of flowers and leaves of Chaerophyllum macrospermum, and Eramurus Spectabilis plant, which reduce AgNO 3 to AgNPs and stabilize the synthesized AgNPs [44].

Photovoltaic properties
To increase photon absorption of phthalocyanines used in the dye sensitized solar cell (DSSC), the effect of AgNP doping on the efficiency was investigated [44][45][46][47][48].The particle size of TiO 2 , which is made into a paste with polyethylene glycol (PEG300) solution, is nanometer in size.TiO 2 , which is used as a photoanode in the DSSC structure, was plastered on a transparent and conductive fluorine-doped tin oxide (FTO) coated slide.TiO 2 kits sintered at 450 C were prepared for dye sensitization.One of three equal volumes of 3 with 1 mM concentration was used for the reference sample.ESAgNP and CMAgNP silver nanoparticles were doped to the other two.The phthalocyanine solutions prepared separately were drip-dried on TiO 2 kits.Then, 50 mM iodide/triiodide I À /I 3 À was used as the electrolyte for the samples.The samples were turned into sandwiches by covering with the other platinum-coated FTO electrode.The current-voltage (I-V) graph of the data obtained from the measurements is given in Figure 7. From the parameters of the photovoltaic properties of the samples given in Table 1, silver nanoparticles contributed to the efficiency.The maximum current density (J m ), maximum voltage (V m ), short circuit current density (J sc ), and open circuit voltage (V oc ) of the photovoltaic parameters of the phthalocyanine compound sensitized DSSC samples were obtained from Figure 7.The fill factor (FF), which expresses the photovoltaic characterization of a solar cell, is calculated from Equation (1).
The efficiency of the AgNP-free reference sample 3 was 1.19.The efficiency increased to 1.45 with ESAgNP silver nanoparticle doping and 1.95 with CMAgNP silver nanoparticle doping.These results indicate that our phthalocyanine compound produced increased photon absorption in harmony with the doped silver nanoparticles.Studies show that more efficient photovoltaic products are obtained as a result of doping with silver nanoparticles and that the particle size of AgNPs is related to cell efficiency [49].Another study concludes that Au@Ag NCs embedded in organic solar cells generate improved plasmonic scattering efficiency.This increases the effect of the quantitative results from 6.39% to 7.29% of the energy conversion effect compared to the control sample [50].

Conclusion
Chaerophyllum macrospermum and Eremurus spectabilis silver nanoparticles were prepared by a green chemistry method.Furthermore, an axial phthalocyanine compound was synthesized.Characterizations of the products were done with TEM, XRD, 1 H NMR, UV-Vis, mass, and FT-IR spectra.Axial phthalocyanine 3 was examined for aggregation behavior.Absorption measurements in different solvents show that the compound has good solubility.Fluorescence emission and excitation spectra of 3 were evaluated for potential applications.Chaerophyllum macrospermum and Eremurus spectabilis silver nanoparticles were added to 3 and photovoltaic parameters were investigated.With addition of silver nanoparticles to 3, the conductivity increased, although still low.These results show that phthalocyanines can be made efficient for dye-sensitized solar cells using silver nanoparticles or different materials.
2 , 64.48 , 77.50 , and 81.55 in CM-AgNP are the characteristic diffraction peaks of Ag (111), (200), (220), (311), and (222) planes.Peaks of diffraction reflections were also observed in AgNP, JCPDS Card No. 04-0783 for the face-centered cubic structure of silver.The average crystal size of CM-AgNPs was calculated as 30.85 nm using the Debye-Scherrer formula, compatible with the TEM results we obtained.The peaks at 2h of 38.1 , 44.28 , 64.50 , 77.4 , and 81.50 in Es-AgNP are characteristic diffraction peaks and correspond to silver's (111), (200), (220), (311), and (222) planes.The peaks of the refraction reflections also seen in this nanoparticle are determined by the JCPDS Card No. Since it is compatible with 00-004-0783, the geometric structure of this nanoparticle is similar to the structure of CM-AgNPs and consistent with studies for face-centered cubic structures[42].

Figure 7 .
Figure 7. J-V curves of 3 with and without AgNP doped.

Table 1 .
Photovoltaic parameters of three with and without AgNP doped.