Matrix Effect of Properties of Au, ZnO and Eu 2 O 3 : Silica, Titania and Alumina Matrices

: The composites Au/SiO 2 , Au/TiO 2 , Au/Al 2 O 3 , ZnO/TiO 2 , ZnO/TiO 2 , ZnO/Al 2 O 3 and Eu 2 O 3 /SiO 2 , Eu 2 O 3 /TiO 2 and Eu 2 O 3 /Al 2 O 3 were prepared using a solid-state method. The effect of the polymer precursors was investigated using two precursor polymers, Chitosan and Poly(styrene-co-4vinylpyridine), (PS-co-4-PVP) in the M/M x L y • Chitosan//M’ x O’ y as well as M/M x L y • PS-co-4-PVP//M’ x O’ y with M’ x O’ y = SiO 2 , TiO 2 and Al 2 O 3 . The effects on the particle size and morphology were observed. The new composites were characterized using X-ray powder diffraction, SEM-EDS mapping and HRTEM analysis. The distribution of the metallic nanoparticles as well as the metal oxide nanoparticles inside the matrices depend on the matrix. Marked optical and photocatalytic effects of the Au, ZnO and Eu 2 O 3 inside the SiO 2 , TiO 2 and Al 2 O 3 matrices are expected. An experiment is in course.


Introduction
Some of the typical properties of nanostructured nanoparticles such as the plasmon, their size, their morphology and band gap depend on the media that surround them [1,2]. For nanoparticles in a solution, their stabilizer and solvents control and/or affect these properties [1,2]. In a solid state, when these nanoparticles are inside of a solid matrix, those properties are affected by the characteristic of the matrix. Scarce studies of the medium on the optical effects and on other properties have been reported, with almost all of them using metallic nanoparticles [2][3][4], and no studies with metal oxide nanoparticles have been reported. For solid states, the optical properties of metal nanoparticles (Au, Ag, and Cu) are greatly influenced by the interface between the nanoparticles and the matrix [1,3,4]. The influence of the structure's environment on the optical properties of some metal noble nanoparticles were recently revised by Tondello and Parkin [3,4]. Matsuoka [5] studied the influences of the dielectric constant of TiO 2 , ZrO 2 and Al 2 O 3 on the optical properties of Au nanoparticles. A direct linear relation between the maxima absorption of the Au nanoparticles with the dielectric constant was found. On the other hand, a solution study of the external dielectric medium (of the solvent) on the surface plasmon resonance spectrum of silver nanoparticles, from an experimental approach as well as a theoretical approach, was reported by Schatz et al. [1,2]. A theoretical study of the influences of the size, shape and dielectric environment on the optical properties of metal nanoparticles in a solution was reported by Schatz et al. [1]. Saviot [6] studied the optical properties of gold and silver inside an alumina matrix. Goutam De [7] studied the optical properties of the nanoclusters of Cu inside silica. Additionally, Torrell studied the functional and optical properties of Au:TiO 2 nanocomposite films [8]. A direct relation between the size of the Au particles and the annealing temperature was found.
Finally, Mattei et al. [9] reported the effect of the ZrO 2 •SiO 2 matrix on the optical properties of silver-doped ZrO 2 . Although the composites M/M' x O' have been studied the most, the composites M x O y /M' x O' y have been scarcely investigated [10][11][12].
Previously, we studied the matrix effect of the medium effect of NiO on the optical properties and catalytic degradation of methylene blue inside the matrices SiO 2 , TiO 2 and Al 2 O 3 [13]. The efficiency of the photocatalytic activity depends on the formation of a p-n junction between NiO acting as p-NiO and the metal oxide matrix acting as an n-metal oxide. TiO 2 presents the most effective p-NiO//n-TiO 2 junction. Moreover, the optical parameters Eg and λ max depend on the dielectric constant and the refractive index of the matrix medium, in a manner of which depends on the preparation procedure [13]. Now, we report the synthesis and characterization of the nanocomposites Au/SiO 2 [14], Au/TiO 2 , Au/Al 2 O 3 , ZnO/SiO 2 [15] [16] for a future study of the optical as well as photocatalytic properties of Au, ZnO and Eu 2 O 3 inside SiO 2 , TiO 2 and Al 2 O 3 matrices. We selected Au as a typical noble metal, ZnO as a typical metal oxide and Eu 2 O 3 as a typical representative of the lanthanide series. As a preparative general method for these composites, we used the solid-state method from the pyrolysis of the precursors M x L y •Chitosan//M' x O' y , where M x L y = AuCl 3 , ZnCl 2 and Eu(NO 3 ) 3 and M' x O' y = SiO 2 , TiO 2 and Al 2 O 3 , using a general previously reported method [13][14][15][16][17][18]. Some preliminary reports of Au/SiO 2 [14], ZnO/SiO 2 [15], Eu 2 O 3 /SiO 2 [16], ReO 3 /SiO 2 [17], Rh/RhO 2 /SiO 2 [18], Rh 2 O 3 /SiO 2 [18], ThO 2 /SiO 2 and ThO 2 /TiO 2 [19] have recently been reported. A general schematic diagram of the method is shown in Figure 1. REVIEW 2 Additionally, Torrell studied the functional and optical properties of Au:TiO2 nanocomposite films [8]. A direct relation between the size of the Au particles and the annealing temperature was found. Finally, Mattei et al. [9] reported the effect of the ZrO2•SiO2 matrix on the optical properties of silver-doped ZrO2. Although the composites M/M´xO´ have been studied the most, the composites MxOy/M´xO´y have been scarcely investigated [10][11][12].
Previously, we studied the matrix effect of the medium effect of NiO on the optical properties and catalytic degradation of methylene blue inside the matrices SiO2, TiO2 and Al2O3 [13]. The efficiency of the photocatalytic activity depends on the formation of a p-n junction between NiO acting as p-NiO and the metal oxide matrix acting as an n-metal oxide. TiO2 presents the most effective p-NiO//n-TiO2 junction. Moreover, the optical parameters Eg and λmax depend on the dielectric constant and the refractive index of the matrix medium, in a manner of which depends on the preparation procedure [13]. Now, we report the synthesis and characterization of the nanocomposites Au/SiO2 [14], Au/TiO2, Au/Al2O3, ZnO/SiO2 [15], ZnO/TiO2, ZnO/Al2O3, Eu2O3/SiO2, Eu2O3/TiO2 and Eu2O3/Al2O3 [16] for a future study of the optical as well as photocatalytic properties of Au, ZnO and Eu2O3 inside SiO2, TiO2 and Al2O3 matrices. We selected Au as a typical noble metal, ZnO as a typical metal oxide and Eu2O3 as a typical representative of the lanthanide series. As a preparative general method for these composites, we used the solid-state method from the pyrolysis of the precursors MxLy •Chitosan//M´XO´y, where MxLy = AuCl3, ZnCl2 and Eu(NO3)3 and M´X O´y = SiO2, TiO2 and Al2O3, using a general previously reported method [13][14][15][16][17][18]. Some preliminary reports of Au/SiO2 [14], ZnO/SiO2 [15], Eu2O3/SiO2 [16], ReO3/SiO2 [17], Rh/RhO2/SiO2 [18], Rh2O3/SiO2 [18], ThO2/SiO2 and ThO2/TiO2 [19] have recently been reported. A general schematic diagram of the method is shown in Figure 1.

Materials and Methods
The composites were prepared according to a previously reported method [13][14][15][16][17][18]. Some experimental details used for the preparation of the composites Au//M´X O´y, ZnO//M´X O´y and Eu2O3//M´X O´y are shown in Supplementary Information S1.

Materials and Common Procedures
AuCl3, ZnCl2 and Eu(NO3)3 from Aldrich (Sigma-Aldrich Quimica Ltda, Chile ) were used as received. Chitosan (Aldrich) of low molecular weight was used as received. An estimation of the molecular weight was performed via viscosimetry. The average molecular weight was determined using the Mark-Houwink equation, and values of [h] were obtained using the parameter previously reported by Rinaudi et al. [20]. The solvent used was an aqueous solution of acetic acid, NaCl and urea. The value was Mw = 61.000.

Materials and Methods
The composites were prepared according to a previously reported method [13][14][15][16][17][18]. Some experimental details used for the preparation of the composites Au//M' x O' y , ZnO// M' x O' y and Eu 2 O 3 //M' x O' y are shown in Supplementary Information S1.

Materials and Common Procedures
AuCl 3 , ZnCl 2 and Eu(NO 3 ) 3 from Aldrich (Sigma-Aldrich Quimica Ltda, Chile) were used as received. Chitosan (Aldrich) of low molecular weight was used as received. An estimation of the molecular weight was performed via viscosimetry. The average molecular weight was determined using the Mark-Houwink equation, and values of [h] were obtained using the parameter previously reported by Rinaudi et al. [20]. The solvent used was an aqueous solution of acetic acid, NaCl and urea. The value was Mw = 61.000. All the reactions were made in CH 2 Cl 2 as solvent. Poly(styrene-co-4vinylpyridine) (Aldrich) with 90% of pyridine groups was used as received.

General Procedure
Metal macromolecular complexes (1)- (18) were prepared according to published procedures [13][14][15][16][17][18]. In a typical synthesis, the respective metallic salt was added in a Schlenk tube over a CH 2 Cl 2 solvent under magnetic stirring and then the respective polymer PSPco-4-PVP or Chitosan was added according to a 1:1 molar ratio. The reaction time and other details for each metallic salt's reaction are given in Table S1 of the Supplementary Information. After this, the supernatant solution (if the solid decanted) was extracted with a syringe, and the solid was dried under a reduced pressure. Further experimental details for the reactions are given in Table S1 of the Supplementary Information. Owing to their insolubility, the characterization of the precursors was made only via IR spectroscopy.

Pyrolysis of the Precursors
The pyrolysis experiments were made by pouring a weighed portion (0.05-0.15 g) of the metal polymer precursor 1-18 into aluminum oxide boats that were placed in a furnace (Daihan oven model Wise Therm FHP-12) under a flow of air, heating from 25 • C to upper temperature limits of 300 • C, and then to 800 • C, followed by annealing for 2-4 h in each case. The heating rate was consistently maintained at 10 • C min −1 for all experiments. Solid pyrolytic samples were characterized via X-ray diffraction of powders (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infra-red (FTIR) spectroscopy. SEM images were acquired with a Philips EM 300 scanning electron microscope. Energy dispersive X-ray analysis (EDAX) was performed on a NORAN Instrument micro-probe attached to a JEOL 5410 scanning electron microscope. TEM data were acquired using a JEOL SX100 and a JEOL 2011 transmission electron microscope. High-resolution transmission electron microscopy (HR-TEM) was performed using a JEOL 2000FX TEM microscope at 200 kV to determine the average particle size, distribution, elemental composition and crystallinity of the samples. The average particle size was calculated using the Digital Micrograph software. The TEM samples were prepared by dispersing pyrolyzed material onto copper grids and dried at room temperature. X-ray diffraction (XRD) was conducted at room temperature on a Siemens D-5000 diffractometer with θ-2θ geometry. The XRD data were collected using Cu-Kα radiation (40 kV, 30 mA). FTIR measurements were performed on a Perkin Elmer FTIR spectrophotometer, Spectrum BXII model.
The HRTEM measurements were made for some representative M x L y •Chitosan//M x O y composites. According to the HRTEM analysis, for the Au/TiO 2 composite, the TiO 2 matrix induced the nucleation of uniform nanoparticles smaller than the Au/Al 2 O 3 composite, and where the Au nanoparticles were bigger and more irregular, they were induced by the Al 2 O 3 matrix (see Figure 2). other hand, strong diffraction peaks from planes (101), (103), (200), (105), (211) and (215) of the TiO2 anatase were observed. A similar XRD diffraction pattern was observed for the ZnO/TiO2 composite from the PS-co-4-PVP precursors. For the ZnO/Al2O3 composite from the Chitosan precursors, strong diffraction peaks from planes (100), (002), (102) and (103) assigned to ZnO are present in their XRD patterns [15]. On the other hand, weak diffraction peaks assigned to planes (014), (110), (300), (105) and (116) of Al2O3 were also observed [13]. A similar XRD pattern from the ZnO/Al2O3 composite from the PS-co-4-PVP polymer was observed. For the Eu2O3/TiO2 composite from Chitosan, an intense plane (211), as well as weak peaks corresponding to planes (123), (411), (600), (543), and (642) of Eu2O3, were observed [16]. On the other hand, for Eu2O3/TiO2 from PS-co-4-PVP, a similar XRD pattern was observed. For the Eu2O3/Al2O3 from Chitosan, owing to the luminescence of the sample, the base line increased as the value of 2θ increased. Despite this, the typical peaks of Eu2O3 and Al2O3 were clearly observed (see Supplementary  Information S2).
The HRTEM measurements were made for some representative MxLy•Chitosan//MxOY composites. According to the HRTEM analysis, for the Au/TiO2 composite, the TiO2 matrix induced the nucleation of uniform nanoparticles smaller than the Au/Al2O3 composite, and where the Au nanoparticles were bigger and more irregular, they were induced by the Al2O3 matrix (see Figure 2). On the other hand, for the ZnO/Al2O3 composite obtained from the Chitosan precursor, some polymorphological shapes were observed (see Figure 3). In addition, some squared and octahedron-shaped nanoparticles (enclosed in red circles) as well as some lamellar areas were observed. On the other hand, for the ZnO/Al 2 O 3 composite obtained from the Chitosan precursor, some polymorphological shapes were observed (see Figure 3). In addition, some squared and octahedron-shaped nanoparticles (enclosed in red circles) as well as some lamellar areas were observed.
For Eu 2 O 3 /SiO 2 (see Figure 4), big shapes were observed, as shown in Figure 4. As for the Eu 2 O 3 /TiO 2 nanoparticles (see Figure 5), big shapes of TiO 2 coated with Eu 2 O 3 were observed. The EDS analysis shown in Figure 5b,c, confirms these features. For Eu2O3/SiO2 (see Figure 4), big shapes were observed, as shown in Figure 4. For Eu2O3/SiO2 (see Figure 4), big shapes were observed, as shown in Figure 4.  Also, in some areas, the nanoparticles of the TiO 2 anatase showing the typical interplanar 0.35 nm corresponding to the (101) plane were observed, as shown in Figure 6, which is in agreement with the findings from the XRD analysis. As for the Eu2O3/TiO2 nanoparticles (see Figure 5), big shapes of TiO2 coated with Eu2O3 were observed. The EDS analysis shown in Figures 5b and 5c, confirms these features. Also, in some areas, the nanoparticles of the TiO2 anatase showing the typical interplanar 0.35 nm corresponding to the (101) plane were observed, as shown in Figure  6, which is in agreement with the findings from the XRD analysis. For the Eu2O3/Al2O3 composite, small "type worms" were observed (see Figure 7). For some of the composites, the distributions of the respective Au, ZnO and Eu2O3 inside the SiO2, TiO2 and Al2O3 matrices were investigated via SEM-EDS mapping. Welldispersed and small Au nanoparticles were observed.
The SEM EDS mapping for the composite Au/SiO2 was previously reported in [14] (see Supplementary Information S3).  For some of the composites, the distributions of the respective Au, ZnO and Eu 2 O 3 inside the SiO 2 , TiO 2 and Al 2 O 3 matrices were investigated via SEM-EDS mapping. Welldispersed and small Au nanoparticles were observed.
The SEM EDS mapping for the composite Au/SiO 2 was previously reported in [14] (see Supplementary Information S3).
For the composite Au/TiO 2 , as shown in Figure 8, a homogeneous distribution of Au nanoparticles inside TiO 2 was observed.
For the composite Au/Al 2 O 3 , the distribution of the Au nanoparticles inside the Al 2 O 3 matrix was not very homogeneous, and some agglomerations of the Au nanoparticles in some zones of the aluminum oxide matrix were observed (see Figure 9). Additionally, there appears to be a matrix effect of the dispersion of the Au nanoparticles inside the Al 2 O 3 matrix.  On the other hand, for the composite ZnO/Al2O3, a near homogeneous distribution of the ZnO nanoparticles inside the Al2O3 matrix was observed (see Figure 10). For the Eu2O3/TiO2 composite, a distribution of very abundant and small Eu2O3 nanoparticles inside TiO2 was observed (see Figure 11). For the Eu 2 O 3 /TiO 2 composite, a distribution of very abundant and small Eu 2 O 3 nanoparticles inside TiO 2 was observed (see Figure 11). On the other hand, for the Eu2O3/Al2O3 composite, a linear sweep study per element was performed. As shown in Figure 12, there are zones where the contents of oxygen and aluminum are high, and the Eu content is lower, suggesting the presence of a minor content of Eu2O3 inside the matrix Al2O3, but it would need to have a higher content to be in accordance with the behavior of Al2O as a matrix. On the other hand, for the Eu 2 O 3 /Al 2 O 3 composite, a linear sweep study per element was performed. As shown in Figure 12, there are zones where the contents of oxygen and aluminum are high, and the Eu content is lower, suggesting the presence of a minor content of Eu 2 O 3 inside the matrix Al 2 O 3 , but it would need to have a higher content to be in accordance with the behavior of Al 2 O as a matrix. Micro 2023, 3, FOR PEER REVIEW 13 Figure 12. Linear sweep SEM EDS per element of the Eu2O3/Al2O3 composite.

Effect of the SiO2, TiO2 and Al2O3 Matrices on the Distribution of Au, ZnO and Eu2O3 inside Them
The SiO2, TiO2 and Al2O3 matrices influence the distribution of the Au, ZnO and Eu2O3 inside them. For Au included in SiO2, a uniform distribution was observed (see Supporting Information S3). On the other hand, for the Au inside TiO2, non-uniform nanoparticles and some agglomerate nanoparticles were observed (see Figure 8). For the Au nanoparticles inside Al2O3 and similar situations, see Figure 9.
For ZnO inside Al2O3, nanoparticles that were not well distributed and some agglomerate nanoparticles of the oxide inside alumina were observed (see Figure 10).
On the other hand, for Eu2O3 inside TiO2, a uniform distribution but very close lanthanide oxide inside the matrix was observed (see Figure 11).

Morphology Effect of the Au, ZnO and Eu2O3 Nanoparticle by the Matrices SiO2, TiO2 and Al2O3
The SEM image of the Au nanoparticles included inside the SiO2, TiO2 and Al2O3 matrices shows some minor effect on the morphology, as shown in the Supporting Information (S4). For the Au inside SiO2 and TiO2, dense agglomerate grains with variated forms were observed, while for the Au inside Al2O3, a "some foam" 3D form was observed.
For the Eu2O3 nanoparticles, the inclusion inside the matrices TiO2 and Al2O3 produces significant changes in their morphology, as shown in the Supporting Information (S5). For Eu2O3 inside TiO2, dense grains of several shapes that were not The SiO 2 , TiO 2 and Al 2 O 3 matrices influence the distribution of the Au, ZnO and Eu 2 O 3 inside them. For Au included in SiO 2 , a uniform distribution was observed (see Supporting Information S3). On the other hand, for the Au inside TiO 2 , non-uniform nanoparticles and some agglomerate nanoparticles were observed (see Figure 8). For the Au nanoparticles inside Al 2 O 3 and similar situations, see Figure 9.
For ZnO inside Al 2 O 3 , nanoparticles that were not well distributed and some agglomerate nanoparticles of the oxide inside alumina were observed (see Figure 10).
On the other hand, for Eu 2 O 3 inside TiO 2 , a uniform distribution but very close lanthanide oxide inside the matrix was observed (see Figure 11). The SEM image of the Au nanoparticles included inside the SiO 2 , TiO 2 and Al 2 O 3 matrices shows some minor effect on the morphology, as shown in the Supporting Information (S4). For the Au inside SiO 2 and TiO 2 , dense agglomerate grains with variated forms were observed, while for the Au inside Al 2 O 3 , a "some foam" 3D form was observed.

Morphology
For the Eu 2 O 3 nanoparticles, the inclusion inside the matrices TiO 2 and Al 2 O 3 produces significant changes in their morphology, as shown in the Supporting Information (S5). For Eu 2 O 3 inside TiO 2 , dense grains of several shapes that were not distributed uniformly were observed. On the other hand, for Eu 2 O 3 inside TiO 2 , a "foam like" morphology was observed.
For the composite ZnO/Al 2 O 3 , a "foam type" morphology was observed, as shown in Supporting Information S6, which is formed by "worms", as shown in Supporting Information S6b, in the most enlarged image. A comparison with the morphology of the ZnO/SiO 2 was not possible because ZnO reacts with SiO 2 to give Zn 2 SiO 4 and SiO 2 [15]. On the other hand, the study for the ZnO/TiO 2 composite is not available.

Au
The morphology of the Au/SiO 2 , Au/TiO 2 and Au/Al 2 O 3 composites depends a lot on the preparation method used. For Au/SiO 2 , rather large grains and agglomerates of various shapes in some areas were observed (see Supplementary Materials S4a), while for the Au/SiO 2 composite obtained from a PE-CVD/RF sputtering route, low-sized particles with a pseudo-spherical shape (cluster-like systems) were observed on the growth surface [21]. On the other hand, SiO 2 /Au hybrid microspheres with a diameter of 200 nm were obtained via the galvanic replacement of SiO 2 /Ag hybrid microspheres and chlorauric acid (HAuCl 4 ) solution [22]. Also, monodispersed nanospheres were obtained via a straightforward one-step method, which was developed to synthesize Au-SiO 2 composite nanospheres [23]. Monodisperse hybrid silica nanospheres that had anilino-methyl on the surfaces were prepared first. The as-prepared hybrid silica nanospheres were then used to obtain Au nanocrystal through the redox reaction of HAuCl 4 and anilino-methyl.

For Au/TiO 2 Composites
Using our current method in the solid state, Au/TiO 2 nanocomposites were obtained that present dense, separated grains of various sizes and shapes (see Supplementary Material S4b). On the other hand, for the Au/TiO 2 composites prepared using a spray hydrolytic method and using a photoreduction technique at 90 • C, non-uniform growth of particle size distribution in spherical morphology were observed. The particle size is in the range of 6.0-6.7 nm [24]. Using electrospinning combined with a calcination treatment, the Au/TiO 2 nanofiber composites were prepared [25].

Au/Al 2 O 3
Using our solid-state method, a "foam" type morphology was observed (see Supplementary Material S4c), and Au@Al 2 O 3 core-shell particles that were mostly spherical in shape with a conical cavity were obtained using a one-step method with continuous-wave fiber laser ablation on an aluminum (Al) plate coated with a gold (Au) monolayer immersed in ethanol [26]. The shape of the nanoparticles was roughly spherical with an average size of approximately 20 nm.
Spherical nanoporous forms of the Au/Al 2 O 3 composite with sizes in the range of 54-293 nm were obtained via a combination of solid-state dewetting of Ag/Au bi-layers and subsequent dealloying [27]. The morphology seen by the SEM shows nanoporous spheres with pore sizes in the range of 11.6-50.4 nm.

ZnO/Al 2 O 3
As can be seen from Figure S6 of the Supplementary Material, the SEM image shows a morphology of a mixture of "worm-like" shapes and continuous zones of metallic foams. This morphology contrasts with that obtained using a method in which the ZnO and Al 2 O 3 sols are mixed to give the mixture of two colloidal sols, which was subjected to a multi-spin-coating process, which exhibits a morphology of dense grains and is united by grain boundaries [28]. On the other hand, a continuous porous morphology was obtained from zinc nitrate (Zn(NO 3 ) 2 ·6H 2 O, Sigma-Aldrich), aluminum nitrate (Al(NO 3 ) 3 x9H 2 O) and NH 3 -H 2 O, followed by the addition of a 1:1 (v/v) solution of NH 3 , precipitation to pH 7 and drying at 100 • C and then at 800 • C [29].
A different ZnO/Al 2 O 3 morphology with a "metallic foam" type morphology was obtained from a mixed suspension of Al 2 O 3 and ZnO powders. Then, the stable mixed suspension spray dried, and the resulting powder was first burned out at 500 • C for 4 h in air, and then sintered in flowing argon at 1400 • C for 2 h [30].
A morphology of the ZnO/Al 2 O 3 composite similar to that obtained by our present method was observed using a solution method starting from the precursors (Zn(CH 3 COO) 2 ·2H 2 O, Merck, 99.5%), urea, NH 2 CONH 2 and bayerite powder, Al(OH) 3 ; in the presence of urea, the collar induced a precipitate, which was calcined at 400 • C [31].
The morphology of the Eu 2 O 3 /TiO 2 composite (see Figure S5a of Supplementary Materials) shows fractured and multiform cubohedrons joined in a disorderly manner. No SEM studies of this type of composite for the comparison of morphologies were found in the literature.
The morphology of the Eu 2 O 3 /Al 2 O 3 composite (see Figure S5b of Supplementary Materials) is of the "metallic foam" type. No SEM studies of similar composites prepared using other methods for the comparison of morphologies were found in the literature.

Conclusions
The composites Au/SiO 2 , Au/TiO 2 , Au/Al 2 O 3 , ZnO/TiO 2 , ZnO/TiO 2 , ZnO/Al 2 O 3 and Eu 2 O 3 /SiO 2 , Eu 2 O 3 /TiO 2 and Eu 2 O 3 /Al 2 O 3 were prepared in a single step, unlike another in a solution that involves at least two stages. The effect of the polymer precursors was investigated using the polymer Chitosan and Poly(styrene-co-4vinylpyridine), (PSco-4-PVP) in the M/M x L y •Chitosan//M' x O' y as well as M/M x L y •PS-co-4-PVP//M' x O' y with M' x O' y = SiO 2 , TiO 2 and Al 2 O 3 . The nanocomposites were obtained in a single step, unlike another in solution that involves at least two stages. SiO 2 induces small and welldistributed Au nanoparticles inside the matrix, while TiO 2 and Al 2 O 3 induce nanoparticles that are not well distributed rather than agglomerate Au nanoparticles inside both matrices.
In relation to morphology, SiO 2 and TiO 2 induce dense agglomerate grains of Au inside with varied forms, while for the Au inside Al 2 O 3 , a "some foam" 3D form was observed. Marked optical and photocatalytic effects of the Au, ZnO and Eu 2 O 3 inside the SiO 2 , TiO 2 and Al 2 O 3 matrices are expected. Those experiments are in course.