WO2013029139A1

WO2013029139A1 - Fluorescent polyaniline nanoparticles

Info

Publication number: WO2013029139A1
Application number: PCT/BR2012/000321
Authority: WO
Inventors: Celso Pinto De Melo; Kleber GOLÇALVES BEZERRA ALVES; César Augusto SOUZA DE ANDRADE; Clécio GOMES DOS SANTOS
Original assignee: Universidade Federal De Pernambuco - Ufpe
Priority date: 2011-08-31
Filing date: 2012-08-29
Publication date: 2013-03-07
Also published as: BRMU9102087U2

Abstract

The present invention has as an inventive step the production of fluorescent polyaniline nanoparticles via a specific process relating to a wet chemistry technique whereby polyaniline (PANI), an oxidizing agent and surfactants are combined, for minimizing problems resulting from aggression to the environment, since organic solvents that are environmentally unfriendly materials are used in the current art, and the aim of said invention is to develop new nanoscale fluorescent systems and to improve the performance of machines that require such nanoparticles. The present invention can be used in the industry of electroluminescent devices, and for labelling biological molecules.

Description

Fluorescent Polyaniline Nanoparticles

Field of the Invention The present invention is applicable to the field of electroluminescent devices, such as organic LEDs, for increasing the luminous performance of fluorescent lamps, pH sensors, fluorescent colloidal inks, energy storage devices, and development of diagnostic fluorescent sensors. of pathologies.

The fluorescent particles of the present invention may also be applied for labeling biological molecules, such as antibodies or DNA, also providing medical and veterinary applications and diagnosing diseases caused by various pathogens.

summary

The present invention is due to the application of a simple procedure described herein for obtaining fluorescent nanoparticles of a conductive polymer. Thus, we describe a simple method of preparation by "wet chemistry" techniques by combining polyaniline (PANI), an oxidizing agent and surfactants to obtain fluorescent materials. In particular, the nanoparticles of the present invention provide, among other advantages, the emission of light at various wavelengths, including in the deep blue range, ensuring - because they form stable dispersions in water - advantageous uses of their fluorescent properties in various ways. applications.

Background: Organic Conductive Polymers have been used in a wide variety of organic electronic devices, including new types of electroluminescent (EL) and light-emitting diode (LED) devices; typically these devices feature the Anode is a transparent material that has the ability to inject holes into the EL material (such as indium tin oxide) and is deposited on a support material such as glass or plastic. Usually, EL material includes fluorescent dyes, fluorescent or phosphorescent metal complexes, conjugated polymers, or a mixture thereof. The cathode is usually a material that has the function of injecting electrons into the EL material.

The commercialization of fluorescent nanoparticles is currently established by many well-known companies, and the particles are produced by joining fluorescent or phosphorescent dyes with polymer particles. These nanoparticles are 30 - 100 nm in size and use an aqueous or water soluble carrier in adjusted amounts to produce an ink with a viscosity and surface tension suitable for application to conventional inkjet printers for printing on appropriate substrates.

The use of fluorescent nanoparticles in the area of biological markers and markers has been widely explored, and immunofluorescent markers consist of fluorescent molecules or particles bound to a specific antibody. These markers are very useful in the medical and clinical diagnostic areas.

For example, US Pat. No. 4,665,024, which relates to a fluorescent marker: The marker is prepared, for example, by chemical or physical bonding between a non-fluorescent polymeric particle and one or more fluorescent dye types, resulting in fluorescent microparticles. Pat. No. 6,344,272 and 6,428,811 describing the use of nanocomposites consisting of electrically conductive coated silica nanoparticles, with applications in the area of controlled drug release. US Pat. No. 5,830,912; 4,774,339; 5,187,288; 5,274,113; 5,433,896; 4,810,636 and 4,812,409 describe the use of non-fluorescent nanoparticles incorporated and / or covalently linked to materials capable of light emission upon excitation (fluorophores) such as pyrene, anthracene, naphthalene, acridine, stilbene, indole, oxazole, thiazole, cyanines, porphyrins, azulene , pyridine, quinoline, pyrene and coumarin and / or combination thereof. Fluorescent inks using water as a dispersion are described in US Pat. No. 6,268,222: These fluorescent particles are obtained by chemical bonding and / or incorporation of polymeric nanoparticles with fluorescent pigments, and incorporation of the pigment is performed after polymerization of the nanoparticle.

Fluorescent nanoparticles are currently widely traded through various companies (Cromeon (Germany), Fluka Biosciences (Germany). These particles are produced in a wide variety of colors (emission), however they are obtained by joining fluorescent dyes with polymeric particles. - for more details see US Patent No. 0293409 A1. The use of conductive polymers in electronic applications has also been extensively explored, as for example in US Patent No. 7,351,358 B2 where colloidal dispersions are produced. Water soluble polypyrrols, used to manufacture organic LEDs (OLEDs), electromagnetic shielding devices, electrochromic dials, field effect transistors and data storage devices.

PI 0805991-8 describes the synthesis of fluorescent nanoparticle composites. More specifically, it relates to the composites themselves, the process of preparing such composites, the rapid diagnostic systems (such as kits) containing such compounds and the use of such composites; in PI 0805991-8 the emission of light in the deep blue and / or green range is achieved by joining a conductive polymer with a metal (polyaniline / gold). The present invention differs from said document in that it does not require the development of composite materials, that is, the joining of two chemically different materials, and therefore the fluorescence of the particles proposed in this patent is obtained from the PANI polymer itself.

The present invention shows a process of synthesis of fluorescent nanoparticles by a single step and using as a vehicle or means of dispersing water, which enables a greater diversity of applications such as, for example, in the areas of human and animal health. use in in vivo formulations in biological systems. Although such documents bear similarity to the present patent, existing differences can be observed by comparing these documents which can be seen in Table I below.

Table I - Comparison between the characteristic components of each invention

Prior Art Problems and Limitations

The main problems encountered in the present state of the art are: the use of organic solvents that are environmentally and biologically aggressive materials, in addition to influencing performance and efficiency by attacking materials, particularly plastics, which in general constitute devices that use these structures. The present invention, as it is the preparation of fluorescent materials that are dissolved in aqueous medium, does not present many of the limitations of use and applications of the usual techniques and can be applied, among others. possibilities, marking of biological molecules and systems in vivo.

In addition, we can highlight that the technique described here does not need and does not require the addition of other spectroscopically active materials, among which we can highlight: fluorescent dyes or pigments, fluorescent or phosphorescent metal complexes. Furthermore, the disclosed technique does not require the use of substrates and / or metallic particles for polyaniline nanoparticles to exhibit the physical property of fluorescence. In this way, additional steps of synthesis and / or insertion of additional particles or molecules are avoided, making the described system more economically viable compared to commercially available systems that make use of unconventional polymers.

Objectives of the Invention The object of the present invention is to present the possibility of preparing fluorescent polyaniline nanoparticles and to discuss their synthesis through a wet chemistry method that combines polyaniline (PANI), an oxidizing agent and surfactants, in order to minimize problems of harm to the environment and improve the performance of devices and appliances using these nanoparticles. The present invention avoids and dispenses with the need for chemical modifications and the use of commercial fluorophores / dyes and / or metal particles which may require special treatment during production and / or disposal in order to avoid becoming contaminants. of soils, effluents and / or food.

The present invention also aims at the development of novel nanoscale fluorescent systems for large scale production and low operating cost. Solution

The inventive act related to the present invention is to obtain fluorescent polyaniline nanoparticles by specific process of wet chemistry technique. This makes this unique synthesis step provide an advantage over the current state of the art by saving time and cost. This synergistic effect of applying the wet chemistry technique to obtain fluorescence is the inventive act requested here. We are tentatively attributing the fluorescence of the polymer to the confinement of its chains in the small domain within the micelle, which should alter its organization form and the dielectric constant of the medium in which they are dispersed. Benefits

One of the advantages is the emission of light in the deep blue and green range, depending on the type of surfactant, the pH of the medium and the oxidation state of the polymer (See Fig. 1), providing the construction and manufacture of electroluminescent devices more efficient.

Water-soluble nanoparticles, as described herein, are not environmentally friendly and do not interfere with the performance of the devices manufactured with them.

These fluorescent nanoparticles may also be used in the manufacture of nanocomposites which simultaneously exhibit the properties of magnetism and fluorescence, and these composites are obtained by incorporating fluorescent nanoparticles into magnetic materials such as superparamagnetic, paramagnetic, ferromagnetic metal oxides or a combination thereof, This represents an additional advantage as said systems can be used for the purification of biological materials and components (such as proteins, DNA, RNA, etc.) and as biosensors for detecting pathologies of interest. From this combination, multifunctional materials (fluorescent and magnetic) can be obtained that have a promising application in the diagnostic area. The nanoparticles of the invention can be prepared to provide different intensities according to pH, which is an advantage as it allows the application of such particulate systems in the area of pH sensors by fluorescence and can be applied in pathology laboratories. clinic, research and teaching laboratories, and industries.

The novelty and the technical effect achieved In summary, the novelty of the present invention is the fluorescence presented by polyaniline particles by wet chemistry technique which, to date, has not been described in the scientific or patent literature, or even identified elsewhere. research or teaching institution. It is our working hypothesis, yet to be confirmed, that confinement of the conjugated polymer within the surfactant micelles predisposes to a maximization of polymer fluorescence by limiting the degree of electronic displacement of the conjugate system. Detailed Description

The following examples are not intended to limit the scope of the invention, but merely to illustrate one of the numerous ways of carrying out the invention.

By "biological material" is meant the group comprising, but not limited to, DNAs, RNAs, proteins, peptides, non-coding RNAs and / or any other biological materials which may be in the form of a single strand.

"Patient genetic material" means the group comprising, but not limited to, the biological material of any organism obtained from a small amount of blood or a simple smear of epithelial or mucosal cells.

"Oxidizing agent" means the group comprising, but not limited to, compounds containing (NH ₄ ) ₂ S20 ₈ , FeCl ₃ , (NH ₄ ) 2 Cr ₂₀ 07, Cu (NO ₃ ) ₂ , CuSO ₄ , CuBr ₂ , CuCl ₂ , CuSO ₄ , or any compound having greater reduction potential than the monomer. "Monomer" means the group comprising, but not limited to, the smallest repetitive unit such as aniline (C ₆ H ₅ NH ₂ ), thiophene (C ₄ H ₄ S), pyrrole (C ₄ H ₅ N) , or precursor molecules of the respective polymers, polyaniline, PEDOT ((Poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate)) and polypyrrole, and / or a mixture thereof.

By "stabilizer" is meant the group comprising, but not limited to, surfactants such as Sodium Dodecyl Sulfate (SDS), Dodecyltrimethylammonium Bromide (DTAB), Catyltrimethylammonium Bromide (CTAB), TRITON X-405 and / or a mixture of the same.

In general, it is possible to arrive at the invention by adding a surfactant to a slightly acidic aqueous solution by stirring it for a period of not less than five minutes to form micelles to receive previously distilled aniline, thereafter an oxidizing agent is added so that the polymerization process is initiated. The assembly is then shaken for at least 12 hours to ensure complete aniline polymerization within the created micelles, and to obtain nanoscale polymeric particles, thereby obtaining the fluorescence potential.

More specifically, the slightly acidic aqueous surfactant solution may be made with amounts of HCl ranging from 0.01M to 0.3M and with amounts of surfactants ranging from 0.05M to 0.25M. The amount of previously dehydrated aniline should be at least 10 mM.

The following example shows a more specific case of realization. Example 1. Synthesis and Characterization of Nanoparticles

Nanoparticle Preparation

Polyaniline nanoparticles (NPs_PANi) were synthesized by the oxidative chemical polymerization method of aniline in aqueous solution containing surfactants. Anionic surfactant: SDS; Cationic Surfactant: DTAB; Nonionic surfactant: TRITON X-405. For this, initially a certain amount of surfactant (0.15M) was added to 20mL of a solution. HCl (0.1M), the whole being stirred at room temperature for 20min before introducing 50mM of aniline. Finally a 30μΜ solution of the oxidant ((NH 4 SzOs)) was added and kept under continuous stirring for 24h.

A precipitate was observed during the preparation of the colloidal dispersions described above and a final pH of approximately 1.8 was found for all samples. Aniline (ANi - C ₆ H ₅ NH ₂ ), used after vacuum distillation, was purchased from Vetec (Brazil). The other compounds were purchased from Aldrich Co. (USA), 99% pure. Measurements were made within 48 hours of obtaining solutions.

Nanoparticle Characterization

15 Absorption spectra in the near-infrared ultraviolet-visible region were obtained on a Cary 5E spectrophotometer (Varian, Australia) in the 300 to 900 nm region using 1 cm optical path quartz cuvettes. Spectra were obtained from colloidal dispersions diluted in deionized water when needed. Photoluminescence properties were verified with a PCI Spectrofluorimeter (ISS, USA) at 20 ± 1 ° C using a quartz cuvette (1 cm and 5 mL). Morphological analyzes were performed using a JSM-5900 scanning electron microscope (SEM) (JEOL, Japan). The samples were mounted on a glass coverslip attached to the sample holder by double sided carbon tape. Subsequently, a thin surface layer of gold was sputtered through a Bal-tec SDS 050 (Japan) metallizer. A NanoZetasizer Nano-ZS90 instrument (Malvern, UK) was used to investigate 0 colloidal samples dispersed in water at 25 ° C; The size was determined by dynamic light scattering of a laser (λ = 633ηητι) at a scattering angle of 90 °, while the electrophoretic mobility method was used to determine the zeta potential (ζ) of the particles.

5th

Nanoparticle Characteristics

In the methodology employed, the compound ((NH4 SaOs) acts as an oxidizing agent, that is, as a polymerization initiator of the aniline. We also use different surfactants as stabilizers for the formed polymeric nanoparticles.

Colloidal dispersions obtained with SDS and DTAB showed good stability, with no evidence of precipitates or aggregate formation. The average diameter of polyaniline nanoparticles using SDS, DTAB and TRITON X-405 in aqueous solution was determined by dynamic light scattering to be of the order of 5.6 nm; 124.7 nm and 242.3 nm, respectively. The mean zeta potential value obtained for SDS, DTAB and TRITON X-405 polyaniline nanoparticles was 60.0 mV; 59.3 mV and 0.72 mV, respectively, indicating the presence of a well-defined Gouy-Chapman layer, which provides stability for colloidal solutions (Kim et al., 2005), in the case of samples prepared with SDS and DTAB. .

Fig. 2 shows the SEM micrographs of PANI_NPs obtained with the different types of surfactants. In Figure 2a NPs with size between 10 nm - 60 nm are observed, while Figs. 2b and 2c illustrate nanostructures between 40 nm - 80 nm in size; and 20 nm - 120 nm, respectively.

Fig. 3 shows the absorption spectra of PANI_NPs prepared with the different surfactants, the absorption spectra of PANI_NPs prepared with SDS and DTAB show the presence of three absorption bands. The first band at 369 nm is associated with the π-π * electronic transitions involving benzenoid and / or quinoid rings. The second (425 nm) and the third band (800 nm) are associated with electronic transitions involving higher and lower energy polaronic bands, respectively (RAY et al, 1989). These results are in line with those discussed in the literature for the absorption spectrum of emerald salt salt doped NIBP, while for those synthesized with TRITON X-405 two absorption bands are observed, at 380 nm and 570 nm, indicating that NIBP is in the base form of emeraldine (WEI et al, 1994).

Fig. 4 shows the changes in PANI_NPs emission spectra at pH values that varied after treatment of the nanoparticles with acid (HCI) and basic (NaOH) solutions.

The fluorescence dependence on the pH of the surfactant polyaniline nanoparticles system was tested in a The results are shown in Fig. 5. The PANI_NPs were excited at 380 nm, with the emission intensity measured in two regions, one between 420nm - 440 nm (curve a), and the other with measured emission. at 470 nm - 480 nm (curve b) as a function of pH. The effect of pH on the fluorescence intensity of the surfactant polyaniline nanoparticle system can be explained in terms of changes in polyaniline absorption, as well established in the literature (Pringsheim et al, 2001), the characteristic of absorption dependence with pH is due to the process of protonation and deprotonation of NIBP in the emerald form, changing from green (emerald salt) to blue (emerald base) and later to the violet (leucoesmeraldine) on deprotonation.

Table II - Values of Φ for different types of polyanilines.

The fluorescence quantum yield (Φ) of PANI_NPs in aqueous solution was obtained by integrating the emission spectrum of PANI_NPs under acidic conditions (Â _exc = 350 nm) and using as standard reference molecule a 0.1 M Quinine Sulphate solution. in H ₂ SO ₄ (o = 0.54%) (Valeur, 2001). We found a Φ = 0.68, 0.19 and 0.29% for the SDS, DTAB and TRITON X-405 polyaniline nanoparticles system, respectively, which are high values of quantum yield when compared with those previously reported in the literature for polyaniline films on metal surfaces (See Table II); In fact, to date no other study reports quantum yield values for pure polyaniline particles.

Claims

1. NANOP FLUORESCENT POLYYLINE ARTICULA characterized by being obtained from a solution containing a surfactant in an aqueous acidic solution where, after stirring for five minutes or more, distilled aniline is added and the resulting solution is stirred for 10 minutes or more. an oxidizing agent is then added, the whole being kept under vigorous stirring for twelve hours or more.

NANOP FLUORESCENT POLYYLINE ARTICULA according to claim 1, characterized in that said oxidizing agent is

(NH ₄ ) 2S ₂ 0 ₈ , FeCl ₃ , (NH ₄ ) ₂ Cr ₂ 0 ₇ , Cu (N0 ₃ ) ₂ , CuS0 ₄ , CuBr ₂ , CuCl ₂ or CuS0 ₄ , or any compound with the greatest reduction potential than the monomer.

Fluorescent polyaniline nanoparticle according to claim 1, characterized in that said stabilizer is

Sodium Dodecyl Sulphate (SDS), Dodecyltrimethylammonium Bromide, (DTAB) or TRITON X-405, or any derivative having surfactant capacity.

Fluorescent polyaniline nanoparticle according to claim 1, characterized in that said monomer is aniline.

Fluorescent polyaniline nanoparticle according to claim 1, characterized in that said monomer is any compound that can be polymerized by the action of the oxidizing agent according to claim 2.

Fluorescent polyaniline nanoparticle according to claims 1, 2, 3 or 4, characterized in that said fluorescent composites comprise particles of about 250 nm in diameter or less.

7. A process for the preparation of NANOP FLUORESCENT ARTICULES, characterized by a step of adding a surfactant to an acidic aqueous solution, which solution is then stirred for not less than five minutes, and by another step where previously distilled aniline is added. Said surfactant-aniline mixture is then stirred for not less than ten minutes until the addition of an oxidizing agent, with the final solution being stirred vigorously for not less than 12 hours.

8. PROCESS FOR PREPARING FLUORESCENT NANOP ARTICLES according to claim 7, characterized in that said oxidizing agent is selected from the group of oxidizing agents comprising (NH ₄ ) ₂ S ₂ Os.

A process for preparing fluoroescent nanoparticles according to claim 7, wherein said stabilizing agent is SDS, DTAB or TRITON.

A process for preparing fluoroescent nanoparticles according to claim 7, wherein said stabilizing agent is any other anionic, cationic or nonionic surfactant.

A process for preparing fluoroescent nanoparticles according to claim 7, wherein said monomer is aniline.

A process for preparing fluoroescent nanoparticles according to claim 7, wherein said monomer is any compound that can be polymerized by the action of the oxidizing agent according to claim 3.

PROCESS FOR PREPARING FLUORESCENT NANOP ARTICLES according to claim 7, characterized in that said solvent is water.

A process for preparing fluoroescent nanoparticles according to claims 7-13, characterized in that said agitation occurs at a speed of between 600 and 1,200 rpm.

USE OF THE FLUORESCENT NANOP ARTICULA IN IT, according to claims 1, 2, 3, 4, 5 or 6 for the manufacture of diagnostic reagents and / or supplies.

Use of the fluorescent nanoparticle on its own according to claims 1, 2, 3, 4, 5 or 6 for the manufacture of electroluminescent devices mixed with at least one fluorescent polymer.

Use of the fluorescent nanoparticle itself as claimed in claims 1, 2, 3, 4, 5 or 6 for the manufacture of organic LED devices or photovoltaic device.

Use of the fluorescent nanoparticle itself according to claims 1, 2, 3, 4, 5 or 6 for the manufacture of fluorescent lamp.

19. USE OF THE FLUORESCENT NANOParticle IN IT, AS REVOLVED- 1 -2 -3 - 4 ^~ 5 ^~ or -67-for the manufacture of a device or substance for rapid detection fluorescence testing of bioterrorism attack or seizure attack. biological weapons.

Use of the fluoroscopic nanoparticle according to claims 1, 2, 3, 4, 5 or 6 for the development and manufacture of sensors and devices.

USE OF THE FLUORESCENT NANOPARTICULATE IN SI according to claims 1, 2, 3, 4, 5 or 6 for the manufacture of devices and substance for labeling native and unfolded proteins.

USE OF THE FLUORESCENT NANOPARTICULATE IN SI according to claims 1, 2, 3, 4, 5 or 6 for manufacturing fluorescent pigment for inks based on organic resins.