Characterization of the Interactions between Titanium Dioxide

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Characterization of the Interactions between Titani-um Dioxide Nanoparticles and Polymethoxyflavones using Surface-Enhanced Raman Spectroscopy Xiaoqiong Cao, Changchu Ma, Zili Gao, Jinkai Zheng, Lili He, David Julian McClements, and Hang Xiao J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b03906 • Publication Date (Web): 21 Nov 2016 Downloaded from http://pubs.acs.org on November 25, 2016

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Journal of Agricultural and Food Chemistry

Characterization of the Interactions between Titanium Dioxide Nanoparticles and Polymethoxyflavones using Surface-Enhanced Raman Spectroscopy Xiaoqiong Cao 1, Changchu Ma 1, Zili Gao1, Jinkai Zheng 1,2, Lili He 1, David Julian McClements1, Hang Xiao 1* 1

Department of Food Science, University of Massachusetts, Amherst, MA 01003, USA

2

Institute of Agro-Products Processing Science and Technology, Chinese Academy of Agricul-

tural Sciences, Beijing, P. R. China

Corresponding Author * Hang Xiao Email: [email protected]

ACS Paragon Plus Environment

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ABSTRACT

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Nano-sized titanium dioxide (TiO2) particles are commonly present in TiO2 food additives

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(E171), and have been associated with potential adverse effects on health. However, little

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knowledge is available regarding the interactions between TiO2 nanoparticles (NPs) and other

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food components such as flavonoids. In this study, we aim to study the molecular interactions

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between TiO2 anatase NPs and three structurally closely related polymethoxyflavones (PMFs,

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flavonoids found in citrus fruits), namely 3ˊ, 4ˊ-didemethylnobiletin (DDN), 5-demethylnobiletin

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(5DN), 5, 3ˊ, 4ˊ-tridemethylnobiletin (TDN) using UV-Vis spectrometry and surface-enhanced

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Raman spectroscopy (SERS). In the UV-Vis absorption spectra, bathochromic effects were ob-

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served after DDN and TDN conjugated with TiO2 NPs. The results from SERS analysis clearly

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demonstrated that DDN and TDN could bind TiO2 NPs with the functional groups 3ˊ-OH and 4ˊ-

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OH on Ring B and formed charge-transfer complexes. However, 5DN with functional groups

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C=O on Ring C and 5-OH on Ring A could not bind TiO2 NPs. Knowledge on the molecular in-

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teractions between TiO2 NPs and food components such as flavonoids will facilitate the under-

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standing of the fate of TiO2 NPs during food processing and in gastrointestinal tract after oral

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consumption.

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KEYWORDS: Titanium dioxide nanoparticles, polymethoxyflavones, interaction, SERS, fla-

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vonoids

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INTRODUCTION

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Titanium dioxide (TiO2) has been widely used as a food additive, in drug delivery materials and

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as an ingredient in cosmetics. TiO2 in anatase and rutile crystal forms is used as whitening and

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anti-caking agent in food products. The current EU Directive 94/36 specification for titanium

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dioxide only permit the anatase form.1 The United States Food and Drug Administration (FDA)

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and the Joint WHO/FAO Expert Committee of Food Additives (JECFA) specification allows

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both forms.1 TiO2 in anatase form is softer and less abrasive, and therefore more commonly used

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in food industry and healthcare products. Four food-grade TiO2 (E171) samples from different

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companies around the world were analyzed for crystal form. Results showed that three of these

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samples were pure anatase form and one of them contained both form (ie., 22% anatase and 78%

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rutile).2 Known as food additive E171, it is found in foods such as sweets, salad dressings and

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icings. The estimated oral exposure of TiO2 for an adult in the US were about 1 mg Ti per kilo-

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gram bodyweight per day.3 However, approximately 36% of the particles in food-grade TiO2

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(E171) are in nano-scale which is less than 100 nm in at least one dimension.3 Foods with the

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highest content of TiO2 NPs include chewing gums, candies and other sweets. The average con-

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tent of TiO2 in chewing gum was found to be around 2 mg/g, and over 93% of it was nano-TiO2.4

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TiO2 NPs have been shown to be distributed to the liver, kidneys, spleen and lung tissues after

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uptake in the gastrointestinal tract.5 Some studies have linked oral exposure of TiO2 NPs in mice

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with potentially adverse health effects, for example, oxidative stress, inflammation,6, 7 and dam-

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age to liver,5 kidney8 and spleen.9 However, pure TiO2 NPs were used in these previous toxicity


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studies without considering the potential effects of food matrix. The fates of TiO2 NPs in com-

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plex food matrix during processing and after oral consumption are not yet clearly understood.

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Reports have shown that co-administrating specific flavonoids reduces inflammatory and oxida-

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tive renal damage induced in rats by TiO2 NPs.10, 11, 12 However, the mechanism underlying these

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effects are largely unknown. Researchers speculated that it may be related to the antioxidant and

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anti-inflammatory properties of flavonoids, but they did not consider the effects of interaction

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between flavonoids and TiO2 NPs.

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TiO2 NPs in anatase form have a specific surface reactivity. Ti atoms on the surface are forced

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by confinement stress to change their coordination from octahedral (hexa-coordinate) to square-

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pyramidal (penta-coordinate). To compensate the coordinative unsaturation, surface Ti atoms can

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bind atoms or molecules from their surrounding environment. 13 It has been reported that surface

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Ti atoms bound electron-donating enediol ligands

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and simultaneously adjusted their coordination to octahedral and changed the electronic proper-

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ties of TiO2, resulting in the formation of charge-transfer (CT) complexes. This chemical proper-

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ty has been used to determine the enediol compound in tea 17 and directly isolate flavonoids from

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plant using TiO2 NPs.13 Due to the complexity of food matrix, there are high chances that the

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TiO2 NPs CT complexes may be formed in food matrix. However, little is known about the for-

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mation of TiO2 NPs CT complexes within food matrix, which greatly limited our understanding

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of the fate of TiO2 NPs in food during food processing and gastrointestinal digestion.

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The objective of this study is to characterize the interactions between TiO2 anatase NPs and

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polymethoxyflavones (PMFs). PMFs are a unique class of flavonoids mainly found in citrus

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fruits. A broad spectrum of beneficial biological effects of PMFs have been reported, such as an-

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ti-inflammation, anti-carcinogenesis, and anti-atherosclerosis.18, 19 In previous studies, our group

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and bidentate benzene derivatives

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has characterized PMFs and explored the interactions between PMFs and casein using SERS. It

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was found that hydroxyl groups on PMFs play a key role in their SERS behavior and the interac-

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tions.20,

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(DDN), 5-demethylnobiletin (5DN) and 5, 3ˊ, 4ˊ-tridemethylnobiletin (TDN) (Figure 1) were

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used as the model flavonoids to understand the structure and function relationship during molec-

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ular interactions between TiO2 NPs and PMFs. We used both UV-vis spectrometry and Surface-

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SERS to study the interaction. UV-vis analysis is commonly used to detect charge-transfer com-

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plexes in various studies.22–27 SERS has been used to study the molecular interaction through the

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enhanced Raman scattering from molecules adsorbed by a nanoparticle. In this TiO2 study,

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SERS is an ideal tool to study the interactions between TiO2 NPs and PMF molecules based on

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the CT enhancement. To the best of our knowledge, this is the first report on the application of

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SERS to study the interactions between TiO2 NPs and dietary flavonoid compounds.

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MATERIALS AND METHODS

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PMFs

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Three

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tridemethylnobiletin (TDN), were chosen to conduct charge-transfer complex studies herein be-

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cause their chemical structures are closely related and contain potential functional groups (Fig.

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1). DDN, 5DN and TDN were synthesized as previously described.29

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In this study, three structurally closely related PMFs, 3ˊ, 4ˊ-didemethylnobiletin

PMFs,

3ˊ,4ˊ-didemethylnobiletin

(DDN),

5-demethylnobiletin

(5DN),

5,3ˊ,4ˊ-

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Titanium Dioxide NPs dispersion


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TiO2 anatase NPs dispersion (5-15 nm) was purchased from US Research Nanomaterials (TX,

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USA). To visualize the TiO2 NPs, small drops (10 µl) of liquid sample were placed on Parafilm.

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Carbon-coated 200 mesh copper grids were placed on top of the liquid drops for 10 seconds. The

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excess liquid sample were wicked away with filter paper and the grids were placed at room tem-

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perature to dry before imaging with a TEM JEOL 2000FX (Japanese Electron Optics Laboratory,

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Tokyo, JAPAN). The particle diameter distribution in water was measured using a combined dy-

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namic light scattering/particle electrophoresis instrument (NanoZS, Malvern Instruments, Mal-

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vern, UK).

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UV-Vis analyses: sample preparation and instrument

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DDN, 5DN or TDN (60 µl, 5 mM in double-distilled water) were mixed with TiO2 NPs disper-

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sion (60µl 1mg/ml in double-distilled water), respectively, for 10 seconds by vortex and incubat-

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ed over night at room temperature. Prior to UV-Vis analyses, PMFs-TiO2 hybrids were centri-

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fuged and rinse with double-distilled water for three times and then diluted to three milliliters.

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The absorption spectra was determined using a SpectraMax M2 Microplate Reader (Molecular

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Devices, CA, USA.)

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SERS sample preparation and instrument

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DDN, 5DN or TDN (5mM in double-distilled water) were mixed with 1 volume of TiO2 NPs

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dispersion (1mg/ml in double-distilled water), respectively, for 10 seconds by vortex and incu-

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bated over night at room temperature. In the dynamic competition experiment, DDN and 5DN in


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ratio 1:1 were firstly mixed together and then mixed with same volume of TiO2 NPs dispersion.

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Prior to SERS analyses, PMFs-TiO2 hybrids were centrifuged and rinsed with double-distilled

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water for three times, sediment was collected, and 2 µl was used to determine the SERS spectra.

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A DXR Raman Microscope (Thermo Scientific, Madison, WI) equipped with a 785 nm excita-

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tion laser and a 50x objective was used. Spectra were collected with a 5.0 mW laser power and a

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50 µm slit aperture for 2 seconds scanning time.

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Data Analysis

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The data obtained from the DXR Raman spectroscopy were analyzed using TQ analyst software,

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version 8.0 (Thermo Fisher Scientific). Second derivative transformation and smoothing were

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achieved to remove spectral noise and separate overlapping bands.

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RESULTS AND DISCUSSION

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Particle size of TiO2 NPs suspension

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The TEM image and size distribution of TiO2 NPs in water were shown in Figure 2. The manu-

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facturer specified that TiO2 NPs had size ranging from 5 to 15 nm. After suspending in water, the

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average hydrodynamic particle size of TiO2 was around 30 nm (Figure 2B).

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Color change and UV-Vis absorption spectra

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Charge-transfer occurs when electrons transfer from absorbed molecule to the empty conduction

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band on TiO2, which decreases the ionization energy (IE) of the electron donor.25 Therefore,


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charge-transfer complexes may often be detected by a color change and a bathochromic shift in

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the UV-vis spectra.22 To determine whether DDN, 5DN and TDN bind to anatase TiO2 NPs, we

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incubated TiO2 NPs with three different PMFs, observed color changes optically and measured

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the absorbance using UV-Vis spectrometer (Fig. 3). When DDN and anatase TiO2 NPs were

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mixed together, a color change from transparence to yellow was observed (Figure 3A). When

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TDN and anatase TiO2 NPs were mixed, a color change from green-yellow to orange was seen.

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Moreover, after centrifugation, a sediment in dark orange red was found in the tubes where DDN

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or TDN was mixed with TiO2 NPs. The sediments were aggregates of PMF-TiO2 NPs CT com-

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plexes. It is noticed that the amount of sediment in TDN + TiO2 NPs mixture was more than that

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formed in DDN + TiO2 NPs mixture. In contrast, no obvious color change or red sediment was

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observed when 5DN was mixed with TiO2 NPs before or after centrifugation (Fig. 3a). These

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results suggested that charge-transfer complexes formed in DDN + TiO2 NPs mixture and TDN

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+TiO2 NPs mixture, but not in 5DN +TiO2 NPs mixture. In Fig. 3b, comparison of the UV-Vis

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absorbance spectra of TiO2 NPs suspension, DDN solution, TDN solution, DDN-TiO2 hybrid,

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and TDN-TiO2 hybrid showed that TiO2 NPs have bound with DDN and TDN. This was evi-

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denced by the fact that the maximal absorbance peaks, 340 nm for DDN and 350 nm for TDN,

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were broadened towards longer wavelengths and reduced in absorbance intensity. The spectrum

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of DDN did not show any absorbance at wavelengths longer than 400 nm, while the spectrum of

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DDN-TiO2 hybrid showed obvious absorbance at 400 - 480 nm. Therefore, there was a color

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change from transparence to yellow when DDN and TiO2 were mixed. The absorbance spectrum

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of TDN showed absorbance at wavelengths up to 440 nm, while the TDN-TiO2 hybrid showed

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obvious absorbance at wavelengths up to 500 nm. This explains the observed color change from

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green-yellow to orange after mixing TDN and TiO2 NPs. These results showed that mixing DDN


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with TiO2 NPs or mixing TDN with TiO2 NPs resulted in a red shift in their absorbance spectra,

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suggesting that there were molecular interactions and direct bindings between these two PMFs

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and TiO2 NPs. On the other hand, 5DN did not show bathochromic effects with TiO2 NPs: no

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broadening or red shift of the absorbance spectra was observed after mixing 5DN and TiO2 NPs,

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suggesting that there was little or no interaction or direct binding between 5DN and TiO2 NPs.

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SERS spectra of PMFs and PMFs-TiO2 hybrids

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The SERS spectra of DDN, 5DN, TND and PMFs-TiO2 hybrids are shown in Fig. 4. In the full

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scale view of the raw spectra (Fig. 4 a), it can be clearly seen that TiO2 NPs had a distinctive

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peak at 155 cm-1, and both DDN-TiO2 and TDN-TiO2 spectra contained this signature peak from

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TiO2 NPs. In the full scale view of the secondary derivative spectra (Fig. 4 b, c and d), the wave

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patterns of DDN and TDN spectra have been changed after mixing with TiO2 NPs, however, the

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wave pattern of the 5DN spectrum still remained the same before and after mixing with TiO2

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NPs.

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The assignments of representative peaks are listed in Table 1. As in other flavone derivatives re-

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ported previously, the 1652 cm-1 peak from 5DN and TDN was assigned to the bending of 5-OH,

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and the peaks near 1600 cm-1 and 1570 cm-1 were assigned to the C=O stretching motion in

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combination with either C2=C3 stretches or ring quioidal stretches.30 No obvious change was

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observed among these peaks after PMFs were mixed with TiO2 NPs suggested that 5-OH and

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C=O were not the functional groups that directly bound with TiO2 NPs. Note that peaks near

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1370 cm-1 which were assigned to Ring A breath from DDN, 5DN and TDN also did not show

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any obvious change in intensity or wavelength after these PMFs were mixed with TiO2 NPs. This


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indicated that A-Ring of PMFs was not involved in binding TiO2 NPs. As can be seen, there

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were peaks near 1315 cm-1 that corresponded to B-Ring breath from DDN, 5DN and TDN. After

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mixing DDN or TDN with TiO2 NPs, these peaks shifted to longer wavelengths (from 1315 to

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1325 cm-1, and from 1316 to 1329 cm-1) and their intensity was considerably enhanced. Howev-

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er, the peaks from 5DN did not shift after its mixing with TiO2 NPs. The above observations

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demonstrated that 3ˊ-OH and 4ˊ-OH in B-Ring of PMFs were the functional groups directly at-

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tached to TiO2 NPs. The strong bands near 1490 cm-1 were also observed in the spectra of DDN-

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TiO2 NPs and TDN-TiO2 NPs hybrid, and they might be attributed to B-Ring CH in-plane bend-

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ing that was presumably due to their repulsive interaction with TiO2 NPs within short distance.

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These observations also suggested that PMF molecules were attached to the TiO2 NPs surface

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through 3ˊ-OH and 4ˊ-OH in B-Ring rather than 5-OH or C=O in A-Ring. This was the reason

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that DDN and TDN could bind to TiO2 NPs and form a charge-transfer complex; and in contrast

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5DN could not bind to TiO2 NPs or form a charge-transfer complex. The DDN-TiO2 NPs and

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TDN-TiO2 NPs CT complexes (red sediment) were used for SERS analysis. However, no 5DN-

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TiO2 NPs CT complexes were formed after mixing 5DN and TiO2 NPs, and only 5DN crystal

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was collected after washing and centrifugation. Therefore, intensity enhancement could be ob-

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served for 5DN crystal compared with 5DN solution (Figure 4C).

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SERS spectra of DDN + 5DN mixture-TiO2 NPs hybrids

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To confirm the results above, a dynamic competition experiment between DDN (3ˊ-OH and 4ˊ-

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OH) and 5DN (5-OH and C=O) was conducted. DDN and 5DN solutions were mixed first, and

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then TiO2 NPs suspension was added to the mixture. Fig. 5 showed the SERS spectrum of DDN


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+ 5DN mixture-TiO2 NPs hybrid along with the spectra of DDN-TiO2 NPs and 5DN-TiO2 NPs

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hybrids. It can be seen that the spectrum wave pattern of the DDN + 5DN mixture-TiO2 NPs hy-

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brid was very similar to that of the DDN-TiO2 NPs hybrid. No peak was observed near 1652 cm-

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1

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of 5-OH in 5DN. This indicates that the molecule bound to TiO2 NPs did not have a 5-OH group.

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The observation of a peak near 1492 cm-1, assigned to B-Ring CH in-plane bending, indicated

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that the molecule bound to TiO2 NPs had the functional groups in B-Ring. These observations

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suggested that in the presence of DDN and 5DN, only DDN could bind TiO2 NPs and form a

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charge-transfer complex.

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Our results demonstrated that the SERS ‘fingerprint’ of PMF and PMF-TiO2 hybrids were very

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distinctive, so they could easily be identified in the spectrum of a mixture. This knowledge pro-

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vided a scientific basic for developing a rapid detection method for TiO2 NPs in a food matrix.

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By knowing which functional groups in flavonoids (such as PMFs) play key roles in binding

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TiO2 NPs, methods could be developed to utilize TiO2 NPs isolate and/or identify certain flavo-

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noids.

in the spectrum of DDN + 5DN mixture-TiO2 NPs hybrid, which corresponded to the bending

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In summary, the interactions between TiO2 NPs and three structurally closely related PMFs,

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DDN, 5DN and TDN were systematically characterized using UV-Vis spectroscopy and SERS.

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DDN and TDN were able to bind TiO2 NPs with the functional groups 3ˊ-OH and 4ˊ-OH on

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Ring B and form charge-transfer complexes with TiO2 NPs. However, 5DN with functional

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groups C=O on Ring C and 5-OH on Ring A could not bind TiO2 NPs. This study provided fun-

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damental knowledge needed for further research on: 1) the gastrointestinal fate and potential ad-


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verse effects of TiO2 NPs after their oral consumption as a part of real food, 2) developing sim-

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ple and fast approaches to detect TiO2 NPs, 3) isolating specific flavonoids from complex food

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matrix using TiO2 NPs.

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Funding Sources

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This study was support by fund from USDA (2014-67021-21598 and 2016-67021-25147). Jinkai

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Zheng was partially supported by China Natural Science Foundation project 31428017.

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REFERENCES

227 228 229 230

(1)

Journal, T. E. Opinion of the Scientific Panel on Food Additives , Flavourings , Processing Aids and Materials in Contact with Food on a Request from the Commission Related to the Safety in Use of Rutile Titanium Dioxide as an Alternative to the Presently Permitted Anatase Form. European Food Safety Authority. 2004, 163, 1–8.

231 232 233

(2)

Yang, Y.; Doudrick, K.; Bi, X.; Hristovski, K.; Herckes, P.; Kaegi, R. Characterization of Food-Grade Titanium Dioxide: The Presence of Nanosized Particles. Environ. Sci. Technol. 2014, 48 (11), 6391-6400.

234 235 236

(3)

Weir, A.; Westerhoff, P.; Fabricius, L.; Hristovski, K.; von Goetz, N. Titanium Dioxide Nanoparticles in Food and Personal Care Products. Environ. Sci. Technol. 2012, 46 (4), 2242–2250.

237 238 239

(4)

Chen, X.; Cheng, B.; Yang, Y.; Cao, A.; Liu, J.; Du, L. Characterization and Preliminary Toxicity Assay of Nano- Titanium Dioxide Additive in Sugar-Coated Chewing Gum. Small. 2013, 9 (9-10), 1765–1774.

240 241 242

(5)

Wang, J.; Zhou, G.; Chen, C.; Yu, H.; Wang, T.; Ma, Y.; Jia, G.; Gao, Y.; Li, B.; Sun, J. Acute Toxicity and Biodistribution of Different Sized Titanium Dioxide Particles in Mice after Oral Administration. Toxicol. Lett. 2007, 168 (2), 176–185.

243 244 245

(6)

Bu, Q.; Yan, G.; Deng, P.; Peng, F.; Lin, H.; Xu, Y.; Cao, Z.; Zhou, T.; Xue, A.; Wang, Y.; et al. NMR-Based Metabonomic Study of the Sub-Acute Toxicity of Titanium Dioxide Nanoparticles in Rats after Oral Administration. Nanotechnology. 2010, 21 (12), 125105.

246 247 248

(7)

Cui, Y.; Gong, X.; Duan, Y.; Li, N.; Hu, R.; Liu, H.; Hong, M.; Zhou, M.; Wang, L.; Wang, H.; et al. Hepatocyte Apoptosis and Its Molecular Mechanisms in Mice Caused by Titanium Dioxide Nanoparticles. J. Hazard. Mater. 2010, 183 (1-3), 874–880.

249 250 251

(8)

Gui, S.; Zhang, Z.; Zheng, L.; Cui, Y.; Liu, X.; Li, N.; Sang, X.; Sun, Q.; Gao, G.; Cheng, Z.; et al. Molecular Mechanism of Kidney Injury of Mice Caused by Exposure to Titanium Dioxide Nanoparticles. J. Hazard. Mater. 2011, 195, 365–370.

252 253 254

(9)

Wang, J.; Li, N.; Zheng, L.; Wang, S.; Wang, Y.; Zhao, X.; Duan, Y.; Cui, Y.; Zhou, M.; Cai, J.; et al. P38-Nrf-2 Signaling Pathway of Oxidative Stress in Mice Caused by Nanoparticulate TiO2. Biol. Trace Elem. Res. 2011, 140 (2), 186–197.

255 256 257 258

(10)

Al-Rasheed, N. M.; Faddah, L. M.; Mohamed, a M.; Abdel Baky, N. a; Mohammad, R. a. Potential Impact of Quercetin and Idebenone against Immuno- Inflammatory and Oxidative Renal Damage Induced in Rats by Titanium Dioxide Nanoparticles Toxicity. J Oleo Sci. 2013, 62 (11), 961–971.


13


Page 14 of 23

259 260 261 262

(11)

Faddah, L. M. Nayira A. Abdel Baky, Nouf M. Al-Rasheed and Nawal M. Al-Rasheed Biochemical Responses of Nanosize Titanium Dioxide in the Heart of Rats Following Administration of Idepenone and Quercetin. African J. Pharm. Pharmacol. 2013, 7 (38), 2639–2651.

263 264 265 266

(12)

Gonzalez, AE.; Charles, CL.; Pacheco, FP.; Ortiz, GG.; Jaramillo, F.; Rincon, AR. Beneficial Effects of Quercetin on Oxidative Stress in Liver and Kidney Induced by Titanium Dioxide (TiO2) Nanoparticles in Rats. Toxicol.Mech. Methods. 2015, 25 (3), 166-175.

267 268 269

(13)

Kurepa, J.; Nakabayashi, R.; Paunesku, T.; Suzuki, M.; Saito, K.; Woloschak, G. E.; Smalle, J. a. Direct Isolation of Flavonoids from Plants Using Ultra-Small Anatase TiO2 Nanoparticles. Plant J. 2014, 77 (3), 443–453.

270 271 272

(14)

Rajh, T.; Chen, L. X.; Lukas, K.; Liu, T.; Thurnauer, M. C.; Tiede, D. M. Surface Restructuring of Nanoparticles: An Efficient Route for Ligand-Metal Oxide Crosstalk. J. Phys. Chem. B 2002, 106 (41), 10543–10552.

273 274 275

(15)

Dugandžić, I. M.; Jovanović, D. J.; Mančić, L. T.; Milošević, O. B.; Ahrenkiel, S. P.; Šaponjić, Z. V.; Nedeljković, J. M. Ultrasonic Spray Pyrolysis of Surface Modified TiO2 Nanoparticles with Dopamine. Mater. Chem. Phys. 2013, 143 (1), 233–239.

276 277 278

(16)

Janković, I. a.; Šaponjić, Z. V.; Čomor, M. I.; Nedeljković, J. M. Surface Modification of Colloidal TiO 2 Nanoparticles with Bidentate Benzene Derivatives. J. Phys. Chem. C 2009, 113 (29), 12645–12652.

279 280 281

(17)

Lee, K.; Chiang, C.; Lin, Z.; Chang, H. Determining Enediol Compounds in Tea Using Surface-Assisted Laser Desorption / Ionization Mass Spectrometry with Titanium Dioxide Nanoparticle Matrices. Rapid Commun. Mass Spectrom. 2007, 21, 2023–2030.

282 283 284

(18)

Middleton, E.; Kandaswami, C.; Theoharides, T. C. The Effects of Plant Flavonoids on Mammalian Cells: Implications for Inflammation, Heart Disease, and Cancer. Pharmacol. Rev. 2000, 52 (4), 673–751.

285 286 287

(19)

Xiao, H.; Yang, C. S.; Li, S.; Jin, H.; Ho, C.-T.; Patel, T. Monodemethylated Polymethoxyflavones from Sweet Orange (Citrus Sinensis) Peel Inhibit Growth of Human Lung Cancer Cells by Apoptosis. Mol. Nutr. Food Res. 2009, 53 (3), 398–406.

288 289

(20)

Ma, C.; Xiao, H.; He, L. Surface-Enhanced Raman Scattering Characterization of Monohydroxylated Polymethoxyflavones. J. Raman Spectrosc. 2016, 47 (8), 901-907.

290 291 292

(21)

He, L.; Zheng, J.; Labuza, T. P.; Xiao, H. A Surface Enhanced Raman Spectroscopic Study of Interactions between Casein and Polymethoxyflavones. J. Raman Spectrosc. 2013, 44 (4), 531–535.


14

Page 15 of 23


293 294 295

(22)

Kaniyankandy, S.; Rawalekar, S.; Sen, A.; Ganguly, B.; Ghosh, H. N. Does Bridging Geometry Influence Interfacial Electron Transfer Dynamics? Case of the Enediol-TiO2 System. J. Phys. Chem. C. 2012, 116 (1), 98–103.

296 297

(23)

Yoshioka, N.; Inoue, H. DNA Binding of Iron ( II ) -Phenanthroline Complexes : Effect of Methyl Substitution on Thermodynamic Parameters. Z. Naturforsch. 2008, 63b, 37-46.

298 299 300

(24)

Paunesku, T.; Rajh, T.; Wiederrecht, G.; Maser, J.; Vogt, S.; Stojic, A.; Protic, M.; Thurnauer, M.; Woloschak, G. Biology of TiO2 –oligonucleotide Nanocomposites. Nat. Mater. 2003, 2 (5), 343–346.

301 302 303

(25)

Ou, Y.; Lin, J.; Zou, H.; Liao, D. Effects of Surface Modification of TiO2 with Ascorbic Acid on Photocatalytic Decolorization of an Azo Dye Reactions and Mechanisms. J. Molecular Catalysis A: Chem. 2005, 241 (1-2), 59–64.

304 305

(26)

Jingyu, W.; Zhihong, L. Preparation of Nanosized Anatase TiO2 and Its Composites at Low Temperature. Progress in Chem. 2007, 19 (7), 1495-1502.

306 307 308

(27)

Wang, S.; Kurepa, J.; Smalle, J. A. N. A. Ultra-Small TiO2 Nanoparticles Disrupt Microtubular Networks in Arabidopsis Thaliana. Plant, Cell & Environ. 2011, 34, 811– 820.

309 310 311

(28)

Osawa, M.; Matsuda, N.; Yoshii, K.; Uchida, I. Charge-Transfer Resonance Raman Process in Surface-Enhanced Raman-Scattering From P-Aminothiophenol Adsorbed on Silver - Herzberg-Teller Contribution. J. Phys. Chem. 1994, 98 (48), 12702–12707.

312 313 314

(29)

Xiao, H.; Yang, C. S.; Li, S.; Jin, H.; Ho, C.-T.; Patel, T. Monodemethylated Polymethoxyflavones from Sweet Orange (Citrus Sinensis) Peel Inhibit Growth of Human Lung Cancer Cells by Apoptosis. Mol. Nutr. Food Res. 2009, 53 (3), 398–406.

315 316 317

(30)

Corredor, C.; Teslova, T.; Cañamares, M. V.; Chen, Z.; Zhang, J.; Lombardi, J. R.; Leona, M. Raman and Surface-Enhanced Raman Spectra of Chrysin, Apigenin and Luteolin. Vib. Spectrosc. 2009, 49 (2), 190–195.

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Figure Legends

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Figure 1. Chemical structures of three PMFs: 3ˊ,4ˊ-didemethylnobiletin (DDN), 5,3ˊ,4ˊ-

322

tridemethylnobiletin (TDN), and 5-demethylnobiletin (5DN). The potential functional groups

323

that may bind to TiO2 NPs were highlighted. Flavonoid rings A, B and C, and atomic numbering

324

were labeled.

325

Figure 2. (a) TEM image of TiO2 NPs used in this study. (b) Particle size distribution of TiO2

326

NPs suspension in water.

327

Figure 3. Photo images (a) and UV-Vis absorbance spectra (b) of TiO2 NPs, DDN, TDN, 5DN

328

and different PMFs-TiO2 hybrids.

329

Figure 4. SERS spectra of TiO2, DDN, 5DN, TND and different PMFs-TiO2 hybrids. (a) Com-

330

mon scale view of the raw spectra. (b), (c) and (d) were the full scale view of the secondary de-

331

rivative spectra of DDN, 5DN, TDN and PMFs-TiO2 hybrids.

332

Figure 5. Secondary derivative spectra of mixtures of DDN-TiO2, DDN-5DN-TiO2 and 5DN-

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TiO2.

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Page 17 of 23

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Table 1 Wavenumbers and assignments of SERS spectra of DDN, DDN+TiO2, 5DN, 5DN+TiO2, TDN and TDN+TiO2. Raman Shift / cm-1 DDN

DDN +TiO2

5DN

5DN+ TiO2

TDN

TDN +TiO

Assignments

2

-

-

1652

1652

1652

1652

5-OH in-plane bending

1615,

1610,

1601,

1601,

1604,

1602,

C=O stretch, C2=C3 stretch

1564

1567

1571

1571

1569

1571

and ring quioidal stretch

1360

1363

1377

1377

1374

1372

A-Ring breath

1315

1325

1312

1312

1316

1329

B-Ring Breath

-

1492

-

-

-

1489

B-Ring CH in-plane bending

-

155

-

-

-

155

TiO2

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Figure 1.

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341


Figure 2.

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19


344

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Figure 3.

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20

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347


Figure 4.

348 349


21


350

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Figure 5.

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TOC

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Characterization of the Interactions between Titanium Dioxide

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