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The present work focuses on the preparation, using a solution process, of flexible conductive nanocomposites based on polyurethane (PU)/polyaniline (PANI) with different mass percentages: 2, 3 and 4%. Because of the low conductivity of the PU + PANI films, these later were doped with inorganic NiCl2. PU + PANI undoped films were synthesized by a “one-shot” process. For doping process, PANI has been doped according to two different methods: The first one consists of the impregnation of the pristine PU + PANI film in a solution of inorganic salt dopant with a solvent (THF) during a soaking time, while the second method uses a “one-shot” process. The structural characterization and conductivity properties of the polymer blends were examined by differential scanning calorimetry, Fourier transform infrared spectroscopy and dielectric measurements spectroscopy. The results show that NiCl2 significatively increases the conductivity compared to pure PU + PANI blends, with better results using the second method of synthesis.

Hydrogenated natural rubber was prepared by the non-catalytic hydrogenation of natural rubber latex (NRL) with diimide generated from oxidation of hydrazine by hydrogen peroxide. The hydrogenated natural rubber (HNR) was characterized by Raman and FTIR spectroscopy. Raman and FTIR spectra showed that the chemical structure of hydrogenated natural rubber tends to be similar to ethylene-propylene-diene-monomer rubber. The thermogravimetric analysis revealed that the thermal-oxidative decomposition resistance of 65% HNR was close to those of EPDM and the thermal-oxidative decomposition behavior of 65% HNR was similar to EPDM. It is interesting that HNR can be a potential alternative to EPDM in terms of thermal-oxidative degradation properties.

Natural rubber (NR), a natural product from the Hevea brasiliensis tree, has been developed as a photosensitive mechanical modifier utilized in lithography-based three-dimensional (3D) printing technology. Here, we transformed NR to photosensitive NR (PNR) by incorporating acrylate groups via chemical modifications. The acrylated NR was blended with a commercial resin (CR) at various rubber contents (0 to 3 wt %) by a simple mixing approach. The blended resin was solidified to pattern the desired specimen using a digital light processing-based 3D printer. The effect of PNR contents on mechanical properties and thermal performance of the printed specimen compared to the neat CR was studied in this work. A printed sample containing 1.5 wt % PNR can increase the elongation ability and impact strength by approximately 59 and 116%, respectively, compared to the neat CR. The microstructure of the printed objects shows a heterogeneous surface consisting of dispersed rubber droplets and a continuous CR matrix. Two glass transition temperatures belonging to the rubber phase and the resin matrix can be observed. The thermal decomposition of the printed part decreased slightly with the elevation in the rubber content. Consequently, the synthesized photosensitive natural rubber could be used as a toughness modifier employed in ultraviolet-curable resin for the light-based 3D printing technology.

In this work, chemical modification of natural rubber in latex stage was focused on a green condition and to improve thermal, ozone and mechanical properties. Two chemical modifications including epoxidation followed by hydrogenation of natural rubber latex (NRL) were carried out continuously in one-pot system. The NRL was treated with in situ performic acid generated from the reaction of formic acid and hydrogen peroxide to obtain partially epoxidized product or epoxidized natural rubber (ENR) latex which was then further modified its residual unsaturated units using hydrazine and hydrogen peroxide to perform hydrogenation reaction. The chemical structure of the obtained modified rubber so called hydrogenated epoxidized natural rubber (HENR) was characterized by 1H-NMR and ATR-FTIR. Two types of HENR including HENR-1 (27 mol% degree of hydrogenation and 17 mol% degree of epoxidation) and HENR-2 (25 mol% degree of hydrogenation and 28 mol% degree of epoxidation) were subjected to investigate their thermal properties compared to the NR, ENR and hydrogenated NR (HNR). It was found that the modified NRs possess higher thermal property and increased Tg as compared to NR, due to both incorporation of epoxide units and reduced unsaturation of the molecular chain. The prepared HENRs were found to maintain the strain induced crystallization character which is the feature of NR. The vulcanized HENR-1 and HENR-2 showed superior tensile strength compared to vulcanized NR. In addition, the oil and ozone resistances of modified NRs were also improved. The preparation of HENR in one-pot latex system is a facile condition and save energy for any solvent recovery. The procedure can be considered as a potential green and sustainable development of NR.

Raman spectroscopy including mapping technique appears as a powerful technique for the characterization of polymer blends like thermoplastic elastomers (TPEs) and thermoplastic vulcanizates (TPVs). The Raman spectra of polymers blends such as natural rubber/polypropylene (NR/PP) and 65% hydrogenated natural rubber/polypropylene (65%HNR/PP) were identified and the phase distribution was determined. The study was driven for the same type of blends in TPEs state and TPVs state obtained after to 2 different processes, either peroxide cure or sulfur cure. The morphology of TPEs and TPVs obtained by Raman spectroscopy were compared and confirmed using scanning electronic microscopy. Raman mapping shows that the phase morphology of NR/PP, 65%HNR/PP, were characterized as continuous rubber phase morphology of the thermoplastic elastomers (TPEs) and a fine dispersion of cross-linked rubber phase in a continuous matrix of the thermoplastic vulcanizates (TPVs). Raman spectroscopy is demonstrated to be a reference to determine the content ratio of each component in the TPVs. Moreover, Raman mapping could be used to calculate the phase size of cross-linked rubber phase dispersed in the thermoplastic vulcanizates (TPVs).

Sustainable composites derived from epoxidized natural rubber (ENR)/silver-substituted zeolite (AgZ)/poly(lactic acid) (PLA) blends possessing antibacterial activity were reported. ENR, herein, acted as an antibacterial promoter providing more hydrophilicity to the composites and facilitating water diffusion. Two methodologies were used to prepare composites, including solution casting (S) as well as solution casting followed by roll milling (SR). Both composites were compared in terms of morphology, AgZ dispersion, water absorption, and antibacterial activity. The shift of Tg and tan δ toward lower temperature of PLA composites consistently confirmed the compatibility between ENR and PLA by DSC and DMA results, respectively. The good AgZ distribution was observed in composites-SR, as confirmed by SEM/EDX. The results of agar disk diffusion susceptibility test showed that PLA, AgZ/PLA, and even ENR/AgZ/PLA composites-S showed no or less inhibition zone; meanwhile, ENR/AgZ/PLA composites-SR showed the significant inhibition zone against both Escherichia coli and Staphylococcus aureus. Besides, the antibacterial activity of the composites was required at least 5 wt% of AgZ. More than 98% inhibition of S. aureus growth by the composites-SR was observed during 2–24 h of cultivation, whereas AgZ/PLA provided the highest inhibition of only 75% at 24 h of cultivation. Hence, the incorporation of ENR enhances the bactericidal activity of the composites. In terms of mechanical properties, incorporating ENR into the composites decreased tensile modulus and strength, but increased the impact strength significantly. Therefore, the developed composites could be promising materials in food and biomedical fields in which antibacterial and impact resistance properties are required.

Microcellular natural rubber (NR) prepared using a supercritical CO2 technology is a promising alternative to replace traditional foaming agent due to environmental concern. Crucial parameters for the foaming process including CO2 saturation time (30, 60, 90, 120, 180) min, pressure (0, 8.5, 10.5, 12.5) MPa, temperature (45, 55, 65, 85) °C, and crosslinking characteristics of NR (pre-vulcanized time at 15 min and 30 min) were orderly conducted. The results obtained showed a decrement of average cell size (less than 10 μm), cell size distribution, and expansion ratio depending on an enhancement of saturation time and pressure. However, the increment of saturation temperature affected the increase in average cell size, cell size distribution, and expansion ratio. In case of the crosslinking behavior, an escalation of the pre-vulcanized time of rubber influenced the decrement in average cell size, cell size distribution and expansion ratio resulting from an elevation of matrix crosslinking.

Undoped ZnO and Zn0.97−xAl0.03MnxO (x = 0, 1, 2 and 3%) nanopowders (NPs) were synthesized by co-precipitation method. They were characterized by X-ray diffraction (XRD), Fourier transformed infrared (FTIR), Raman, UV–visible, photoluminescence (PL) and impedance spectroscopies. All samples exhibit a single phase wurtzite type. The average crystallite size lying between 22 and 42 nm was found to increase for all doped ZnO samples. The optical transmission in the visible region was improved due to doping. The optical band gap is in the range of 3–3.4 eV and was found to decrease up to 2% of Mn content but slightly increases with further doping. All PL spectra exhibit two emission peaks in UV and visible regions. The deconvolution of the visible emission peak reveals different emissions for all samples. An additional yellow emission is noticed for (Al + Mn) ZnO doped samples suggesting that the incorporation of aluminum and manganese in the zinc oxide host lattice enhances luminescence properties of ZnO. The ac conductivity (σac) was found to follow Jonscher’s power law and was improved with doping. Cole-Cole plots of all samples were suitably fitted to a circuit consisting in a parallel combination of a resistance and a constant phase element (CPE). Keywords: ZnO nanopowder, Doping, XRD, Optical properties, Conductivity

ZnO nanoparticles (ZnO NPs) were synthesized through surfactant free non-hydrolytic organic phase method in which zinc acetate and zinc acetylacetonate were selected as precursors. Structural and size analysis of the as-prepared nanoparticles performed on X-ray diffractometer, transmission electron microscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy showed that the obtained nanoparticles were crystalline particles with all reflections matching to wurtzite. TEM images revealed that ZnO NPs from synthesis in which zinc acetate involved as precursor had a shape of sphere while zinc acetylacetonate resulted in rod-shaped nanoparticles. Reaction rates from catalytic activity test performed on Methylene Blue dye (MB) were found to be 2.99×10-2 min-1 and 1.98×10-2 min-1 for spherical and rod-shaped ZnO NPs, respectively. Antibacterial activity experiments shows rod-shaped ZnO NPs almost completely (99.75%) inhibited the growth of Escherichia Coli while only around 6.5% was survived after treatment of spherical ZnO NPs under same conditions.

Red blood cells of mammals contain both raw carbonaceous material (proteins) and catalyzer precursor (iron atoms of metal-organic hemoglobin molecules) for Carbon nanotube (CNT) fabrication by the chemical vapor deposition method. To demonstrate the possibility of CNT fabrication by using blood as a single raw material, livestock (sheep) blood droplets on silicon substrates were used as samples for pyrolysis in an argon and argon + butane atmosphere at 300; 400; 500; 7000 C. Scanning electron microscope (SEM) images, of the product of pyrolysis at 500; 7000 C, magnified up to 20000 times, shows dense bushes consisting of nano-size rods. The length of the rods reached 50 μm; widths were around 400 nm and less. The two carbon bands centered at wavenumbers 1340 and 1580 cm-1 in the Raman spectra of samples recorded using a low power-incident red laser (638 nm), demonstrates increasing graphitization of carbon atoms with rise of pyrolysis temperature. Both the SEM images and the Raman spectra indicate increasing formation of CNT, with an increase of pyrolysis temperature from 400 to 7000 C. No evidence of CNT formation at 3000 C was found.

The ozone stability of partially hydrogenated natural rubbers (HNRs) was evaluated. HNRs with the hydrogenation levels of 14, 33 and 65 mol% including with vulcanization systems of peroxide and sulfur on ozone stability comparing with natural rubber (NR) and ethylene-propylene-diene-rubber (EPDM) vulcanizates were studied. The chemical structures of rubber vulcanizates were characterized by Raman spectroscopy. The surface cracks were observed by Raman optical microscopy. The results clearly exhibited that the ozone stability of HNRs vulcanizates was much greater than that of the NR vulcanizates. The difference between the integral intensities of C=C bonds of isoprene units in rubber chains by Raman spectroscopy before and after ozone exposed was minimized with the degree of hydrogenation. The depth of cracking observed by three-dimensional (3D) modes clearly decreased with an increase in the degree of hydrogenation, while no cracks on the surface of EPDM were found. These findings indicated that ozone stability increased with the degree of hydrogenation. Regarding the effect of vulcanizing systems, sulfur cure showed greater resistance to ozone degradation than peroxide cure.

Highlights: • We studied the evolutions of structure for TiO{sub 2} thin film as changes with Nb doping and temperatures. • Up to 800 °C, the grain size of Nb{sub 0.1}Ti{sub 0.9}O{sub 2} is smaller than for pure TiO{sub 2} because doped Nb hinders the growth of the TiO{sub 2} grains. • There was no formation of the rutile phase at high temperature. • Nb doped TiO{sub 2} films have high electron densities at 400–700 °C. • Nb dope extends the absorbance spectra of TiO{sub 2} which leads to the band gap reduce. - Abstract: Acid-catalyzed sol–gel and spin-coating methods were used to prepare Nb-doped TiO{sub 2} thin film. In this work, we studied the effect of niobium doping on the structure, surface, and absorption properties of TiO{sub 2} by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectometry (XRR), X-ray photoelectron spectroscopy (XPS), Raman, and UV–vis absorption spectroscopy at various annealing temperatures. EDX spectra show that the Nb:Ti atomic ratios of the niobium-doped titania films are in good agreement with the nominal values (5 and 10%). XPS results suggest that charge compensation is achieved by the formation of Ti vacancies. Specific niobium phases are not observed, thus confirming thatmore » niobium is well incorporated into the titania crystal lattice. Thin films are amorphous at room temperature and the formation of anatase phase appeared at an annealing temperature close to 400 °C. The rutile phase was not observed even at 900 °C (XRD and Raman spectroscopy). Grain sizes and electron densities increased when the temperature was raised. Nb-doped films have higher electron densities and lower grain sizes due to niobium doping. Grain size inhibition can be explained by lattice stress induced by the incorporation of larger Nb{sup 5+} ions into the lattice. The band gap energy of indirect transition of the TiO{sub 2} thin films was calculated to be about 3.03 eV. After niobium doping, it decreased to 2.40 eV.« less

We report the preparation and characterization of spherical core-shell structured Fe3O4-Au magnetic nanoparticles, modified with two component self-assembled monolayers (SAMs) consisting of 3-mercaptophenylboronic acid (3-MBA) and 1-decanethiol (1-DT). The rapid and room temperature synthesis of magnetic nanoparticles was achieved using the hydroxylamine reduction of HAuCl4 on the surface of ethylenediaminetetraacetic acid (EDTA)-immobilized iron (magnetite Fe3O4) nanoparticles in the presence of an aqueous solution of hexadecyltrimetylammonium bromide (CTAB) as a dispersant. The reduction of gold on the surface of Fe3O4 nanoparticles exhibits a uniform, highly stable, and narrow particle size distribution of Fe3O4-Au nanoparticles with an average diameter of 9 +/- 2 nm. The saturation magnetization value for the resulting nanoparticles was found to be 15 emu/g at 298 K. Subsequent surface modification with SAMs against glucoside moieties on the surface of bacteria provided effective magnetic separation. Comparison of the bacteria capturing efficiency, by means of different molecular recognition agents 3-MBA, 1-DT and the mixed monolayer of 3-MBA and 1-DT was presented. The best capturing efficiency of E. coli was achieved with the mixed monolayer of 3-MBA and 1-DT-modified nanoparticles. Molecular specificity and selectivity were also demonstrated by comparing the surface-enhanced Raman scattering (SERS) spectrum of E. coli-nanoparticle conjugates with bacterial growth media.

In this paper, we present a new device composed of a biological part included in an original opto-electronic bioreactor described here in detail. It allows the simultaneous measurement of bioluminescence and optical density of a bioluminescent bacterial culture without any sampling. The cell density is measured through a laser diode and a photodiode by using a numerical synchronous detection and the bioluminescence with a photomultiplier. The experimental results are presented through the validation of the measurement principle using the Vibrio fischeri bacterium which was cultivated under continuous culture conditions. Very good correlation between manual and automatic measurements processed with the instrument has been demonstrated. The device could be applied to the realization of biosensors with any bioluminescent cells.

This article presents a new device devoted to the simultaneous measurement of bioluminescence and optical density of a bioluminescent bacterial culture. It features an optoelectronic bioreactor with a fully autoclavable module, in which the bioluminescent bacteria are cultivated, a modulated laser diode dedicated to optical density measurement, and a detection head for the acquisition of both bioluminescence and optical density signals. Light is detected through a bifurcated fiber bundle. This setup allows the simultaneous estimation of the bioluminescence and the cell density of the culture medium without any sampling. The bioluminescence is measured through a highly sensitive photomultiplier unit which has been photometrically calibrated to allow light flux measurements. This was achieved by considering the bioluminescence spectrum and the full optical transmission of the device. The instrument makes it possible to measure a very weak light flux of only a few pW. The optical density is determined throug...

Bayram, Cem/0000-0001-8717-4668; Cetin, Demet/0000-0003-1186-4229; SULUDERE, ZEKIYE/0000-0002-1207-5814; Tamer, Ugur/0000-0001-9989-6123; Greneche, Jean-Marc/0000-0001-7309-8633; Lagarde, Fabienne/0000-0002-4015-4376 WOS: 000341752200001 The high product yield of multi-branched core-shell Fe3-x O-4@Au magnetic nanoparticles was synthesized used as magnetic separation platform and surface-enhanced Raman scattering (SERS) substrates. The multi-branched magnetic nanoparticles were prepared by a seed-mediated growth approach using magnetic gold nanospheres as the seeds and subsequent reduction of metal salt with ascorbic acid in the presence of a stabilizing agent chitosan biopolymer and silver ions. The anisotropic growth of nanoparticles was observed in the presence of chitosan polymer matrix resulting in multi-branched nanoparticles with a diameter over 100 nm, and silver ions also play a crucial role on the growth of multi-branched nanoparticles. We propose the mechanism of the formation of multi-branched nanoparticles while the properties of nanoparticles embedded in chitosan matrix are discussed. The surface morphology of nanoparticles was characterized with transmission electron microscopy, scanning electron microscopy, ultraviolet visible spectroscopy (UV-Vis), X-ray diffraction, and fourier transform infrared spectroscopy and Fe-57 Mossbauer spectrometry. Additionally, the magnetic properties of the nanoparticles were also examined. We also demonstrated that the synthesized Fe3-x O-4@Au multi-branched nanoparticle is capable of targeted separation of pathogens from matrix and sensing as SERS substrates. Scientific and Technological Research Council (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [108T794, 111T983]; Gazi BAPGazi University [05/2004-03, 05/2011-69] This work was supported by the Scientific and Technological Research Council (TUBITAK) grant numbers 108T794 and 111T983. We also acknowledge support from Gazi BAP, project number 05/2004-03 and 05/2011-69. We would like to thank Gokhan Demirel and Mehmet Yilmaz for 3D simulation. We also thank to Dr Saime Sebnem Cetin and Prof.Dr. Suleyman Ozcelik for XRD measurements.

Using the Rietveld profile method, the atomic coordinates and anisotropic temperature factors of KCaF3 were refined. At room temperature, KCaF3 crystallizes in monoclinic B21/m symmetry, with the lattice parameters: a=8.754(2) Å, b=8.765(4) Å, c=8.760(5) Å, β=90.48(3)°, V=672.1(3) Å3, Z=8. The refinement procedure was stopped when RB=0.05 and the Durbin–Watson statistic factor=0.85 had been reached. The structure determined is related to the tilting of CaF6 octahedra of the a−b+c− type, which are responsible for the monoclinic distortion in perovskite crystals.

Natural rubber/styrene-butadiene rubber (NR/SBR) blends, with and without silica, were prepared by co-coagulating the mixture of rubber latices and various amounts of well-dispersed silica suspension. An attempt to predict blend compositions was made using Raman spectroscopy in association with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was found that the intensity of each Raman characteristic peak was strongly dependent on the blend composition, but there was no significant evolution with the presence of silica. Also, TGA results revealed an improvement in thermal stability of NR/SBR blends with increasing both SBR and silica contents due to the dilution effect. Two distinct glass transition temperatures (Tg) were observed in DSC thermograms of all blends, and their Tg values were independent on both blend composition and silica content. This indicated a physical blend formation, which agreed well with no shifts in Raman peaks of the blends in comparison with those of the individual rubbers. Linear regression with R2 quality factor close to 0.99 was achieved when plotting intensity ratio at 1371/1302 cm−1 versus blend ratios. On the other hand, the peak height ratio and heat capacity ratio from TGA and DSC analysis, respectively, yielded quadratic equations as a function of blend ratios.

Salmonella is a major cause of foodborne illness worldwide and is not allowed to be present in any food in all countries. The purpose of this study is to develop a simple alternative method for the detection of Salmonella based on functionalized polyethylene (PE) surfaces. Salmonella Typhimurium was used as a model bacterium. PE film was treated using dielectric plasma in order to alter the wettability of the PE surface and consequently introduce functionality on the surface. The PE film characterized by ATR-FTIR spectroscopy revealed the presence of C O stretching of ketones, aldehydes and carboxylic acids. The antibodies against O or H antigens of Salmonella and S. Typhimurium were then respectively immobilized on the PE surface after activation of the carboxylic group using NHS/EDC followed by protein A. The evidences from ATR-FTIR, scanning electron microscopy and optical microscopy showed the presence of S. Typhimurium attached to the plasma treated PE surfaces via the two types of anti-Salmonella antibody. The plasma treated PE film developed is simple and allows efficient association of bacterial cells on the treated surfaces without the necessity of time-consuming centrifugation and washing steps for isolation of the cells. This material is considered to be a smart material applicable for S. Typhimurium detection.

This research study deals with the on-line detection of heavy metals and toxicity within the context of environmental pollution monitoring. It describes the construction and the proof of concept of a multi-channel bioluminescent bacterial biosensor in immobilized phase: Lumisens3. This new versatile device, designed for the non-stop analysis of water pollution, enables the insertion of any bioluminescent strains (inducible or constitutive), immobilized in a multi-well removable card. The technical design of Lumisens3 has benefited from both a classical and a robust approach and includes four main parts: (1) a dedicated removable card contains 64 wells, 3 mm in depth, arranged in eight grooves within which bacteria are immobilized, (2) this card is incubated on a Pelletier block with a CCD cooled camera on top for bioluminescence monitoring, (3) a fluidic network feeds the card with the sample to be analyzed and finally (4) a dedicated computer interface, BIOLUX 1.0, controls all the elements of the biosensor, allowing it to operate autonomously. The proof of concept of this biosensor was performed using a set of four bioluminescent bacteria (Escherichia coli DH1 pBzntlux, pBarslux, pBcoplux, and E. coli XL1 pBfiluxCDABE) in the online detection of CdCl(2) 0.5 μM and As(2)O(3) 5 μM from an influent. When considering metals individually, the "fingerprints" from the biosensor were as expected. However, when metals were mixed together, cross reaction and synergistic effects were detected. This biosensor allowed us to demonstrate the simultaneous on-line cross detection of one or several heavy metals as well as the measurement of the overall toxicity of the sample.

This paper investigates the structural characteristics of polystyrene (PS) grafted on a natural rubber (NR) surface using Raman scattering spectroscopy. The nitroxide-mediated radical polymerization (NMRP) technique was used to achieve the graft copolymerization of PS onto the surface of NR film using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a nitroxide mediator. The reversible reaction between propagating radical and TEMPO of the NMRP process leads to a controlled radical polymerization of styrene on the NR surface. The grafting degree of PS on the NR was first measured by gravimetric methods. It was found to depend linearly on the grafting time. The characteristic signals detected by Raman scattering and by attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy provide clear evidence of the PS being grafted onto the NR. The distribution of the grafted PS on the NR substrate was determined from the Raman mapping. It is seen that the grafting occurs homogeneously over the entire surface (∼40 mole % PS). The study using the Raman depth profiling technique on the original sample compared with the analysis carried out on the sample prepared by cross-sectioning led to important and comparable information regarding the uniform distribution of PS grafting inside the substrate.

The study of $(1\ensuremath{-}x){\text{PbMg}}_{1/3}{\text{Nb}}_{2/3}{\text{O}}_{3}\text{\ensuremath{-}}x{\text{PbTiO}}_{3}$ (PMN-PT) single crystals where $x$ is 0, 0.09, 0.21, 0.28, 0.32, 0.35, and 0.38 was carried out with the use of x-ray, dielectric, and Raman scattering techniques in a wide temperature range. In this work, special attention was paid to the analysis of the Raman spectra. However, the results of the structural and dielectric studies were used to better interpret the Raman features. On the basis of the results of these studies, a phase diagram is given. The investigations confirmed that with the increase in the ${\text{PbTiO}}_{3}$ (PT) content the relaxor behavior becomes ferroelectric and that structural phase transitions of different types are observed. Raman studies were performed in a broad temperature range for all concentrations to understand the complex behavior of the PMN-PT system. The origin of the high temperature Raman spectra is considered in the whole concentration range and an origin of these spectra is proposed. For pure PMN and the solid solutions with a Ti content lower than 0.21, the 1:1 chemical order in the $B$-ion sublattice leads to the appearance of clusters with $Fm\overline{3}m$ symmetry. For higher PT contents, the high temperature Raman spectra seem to originate from the polar nanoregions of rhombohedral or tetragonal symmetry. All of the obtained Raman results are interpreted with the use of the group theory analysis. These results confirmed that the symmetries determined from the x-ray diffraction are average ones and play the role of a matrix in which nanoregions with a distinct local symmetry (generally monoclinic) are embedded. The analysis of the Raman spectra allowed us to determine the temperature and composition dependences of the Raman line frequencies, the reduced intensities, and the widths, providing clear evidence for the occurrence of the phase transitions. The anomalous behavior of the line width of some Raman lines related to the Pb ion vibrations pointed to the special role of Pb ion dynamics in the mechanism of phase transitions in the PMN-PT system.