USE OF MOISTURE-SENSITIVE PHOSPHORESCENCE CARBON DOTS AS A SAFETY DEVICE

Description

1 / 30 USE OF MOISTURE-SENSITIVE PHOSPHORESCENCE CARBON DOTS AS A SAFETY DEVICE

[001] The present invention extends to the use of moisture-sensitive carbon dots as a security device for encoding data through inkjet printing. Counterfeiting is a recurring problem that generates trillions of dollars in losses for the world economy. In addition to the economic consequences due to the counterfeiting of consumer goods and luxury items, counterfeiting presents great risks to human health, such as the sale of counterfeit medicines and prescriptions, as well as products with contaminant levels outside the standards permitted by the World Health Organization (WHO). According to the International Chamber of Commerce (ICC), the economic impacts of counterfeiting and piracy on the global economy are in the trillions, reaching US$ 4.7 trillion in 2022 and at the cost of 5 million legitimate jobs (HAMILTON et al., 2016; (ICC), [n.d.]; KATUMO et al., 2022a; MACKEY; LIANG, 2011).However, there is a significant effort in developing non-clonable labels with the highest level of security. Currently, there are two main classes of anti-counterfeiting: 1) Each label must be unique and non-clonable, irremovably attached to each product, making duplication impossible, but this generates significant overloads on information storage systems for data authentication and high costs; 2) The use of interchangeable labels with unique codes for each batch or type of a given product; however, these labels can be more easily forged and used on various products even if they are not from the original batch (ARPPE-TABBARA; TABBARA; S0RENSEN, 2019; KATUMO et al., 2022b). Therefore, there is always a search for new systems or materials that can encrypt or conceal information more effectively.Single-level (with only one emission), double-level (emissions at different wavelengths or different lifetimes), and multilevel (diverse emissions) luminescent materials have been widely used in data encoding (YU; ZHANG; YU, 2021). However, most of these materials, especially the multilevel ones, have toxic metals in their composition, limiting their use due to the associated toxicity. However, the recent discovery of nanoparticles... Petition 870250065394, dated 07 / 29 / 2025, page 4 / 46 2 / 30 carbon-based, metal-free multi-emission technology has become an undeniable alternative for data encoding. This innovation proposal is based on printing carbon dots with moisture-sensitive phosphorescence using a conventional inkjet printer, which offers advantages such as simplicity, speed, flexibility, high resolution, deposition over large areas without contamination, minimal waste generation, low cost, efficient mass production, and wide-ranging information processing possibilities. Furthermore, it has great potential in the manufacture of solar cells, medical devices, sensors, and paper-based data encoding. Background of the invention

[002] In recent decades, nanotechnology materials and techniques have stood out for enabling improvements in data encoding, allowing for advanced security, and making anti-fraud and authentication systems more efficient and secure. In this context, the use of nanomaterials with tunable photoluminescence (PL) emissions associated with inkjet printing has stood out in data encoding.These materials can be tunable by: i) size, as is the case with metallic quantum dots (QDs) of CdSe, CdTe and PBS, which can undergo emission adjustments by altering the size of the nanoparticle or doping with other ions and are normally applied in LEDs, bioimaging and lasers; ii) composition, such as rare earth nanophosphors where the IF tuning occurs according to the matrix composition and doping, mainly with Eu3+, Tb3+, Er3+ and Dy3+ ions, as well as MOFs (Metal-Organic Frameworks) alter the IF according to the exchange of structural components such as organic ligands or metal centers; iii) environment and functionalization, such as carbon nanoparticles (Carbon Dots - CDs), which have controllable emissions according to their chemical composition, surface functionalization with nitrogenous, oxygenated, sulfurous groups, among others, as well as doping, especially with N, S and P.Carbon dots also undergo changes in fluid efficiency (FL) depending on the environment, such as the pH and polarity of the medium in which they are found. Petition 870250065394, dated 07 / 29 / 2025, page 5 / 46 3 / 30

[003] In this context, since their discovery in 2004, Carbon Dots have been one of the most extensively investigated classes of nanomaterials, as they present multiple comparative advantages, such as the absence of heavy metals and rare earths, low cost of large-scale production, low toxicity in relation to biological systems and excellent responses to different physical and chemical stimuli, characteristics of high relevance in the creation of an industrial-scale data coding system.

[004] Additionally, the most investigated CD photoluminescence to date is aqueous fluorescence, which has a very short lifetime for these materials, on the nanosecond (ns) scale (FAN et al., 2014; ZHOU et al., 2017; ZHU et al., 2013), as well as the control of the luminescent emission region (DUNG et al., 2019; JIANG et al., 2015; LIU; YE; MAO, 2007). However, due to the discovery of a wide variety of organic precursors and different synthesis routes, several optical phenomena can be observed, such as thermally activated delayed fluorescence (HOU et al., 2015), chemiluminescence (LIN et al., 2011), electroluminescence (ZHENG et al., 2009), upconversion (ZHUO; SHAO; LEE, 2012), near-infrared luminescence (LU et al., 2017), mechanoluminescence (LIU et al., 2018) and, especially, phosphorescence (DENG et al., 2013a).

[005] In 2012, Lin et al. first reported room temperature phosphorescence (FTA) in solid-state CD particles; however, this strong and stable FTA occurred with Pb2+ doping in the carbon structure (LIN et al., 2012). However, the presence of the heavy metal ion did not generate much interest in this phenomenon, since materials with long FTA lifetimes already exist, such as conventional inorganic phosphors containing heavy metals and rare earths; in addition to limiting various applications due to high biological toxicity and being non-renewable materials (XU; TANABE, 2019). Pure organic materials with residual glow under ambient conditions are rare because the spin-orbit coupling (ASO) of electrons is very weak and the efficiency of delocalized electron transitions is high. Petition 870250065394, dated 07 / 29 / 2025, page 6 / 46 4 / 30 triplet is very low in addition to being easily extinguished by atmospheric heat and oxygen (CAI et al., 2018; HE et al., 2017; XU et al., 2016).

[006] In 2013, almost 10 years after the discovery of fluorescence in exclusively organic carbon nanoparticles free of metals, afterglow (post-glow, residual glow or phosphorescence) was discovered, which is a rather intriguing phenomenon and this emission from CDs triggered several studies in the area and has been successfully applied in advanced fields such as anti-counterfeiting, information encoding and detection, due to its long lifespan after removal of the excitation source (DENG et al., 2013a; JIANG et al., 2020a; SUN et al., 2020).

[007] The long-lasting afterglow of carbon-based nanomaterials is mainly attributed to emissions related to the excited triplet state resulting in phosphorescence. Phosphorescence is a forbidden radiative electronic transition from the lowest energy excited triplet state (Ti) to the ground state (S0), after intersystem crossing (CIS) from the singlet state S1 to the triplet state T1e. On the other hand, delayed fluorescence (RF) is a radiative transition from the lowest singlet state (Si) to S0 after the reverse intersystem crossing (CISR) process, which is the return of the triplet exciton (Ti) to the lowest energy excited singlet state (Si) (JIANG et al., 2020a; XU et al., 2016; ZHAO et al., 2013, 2016). This phenomenon is sometimes referred to as triplet annihilation.

[008] FTA emission in CDs is mainly attributed to the presence of C=O and C=N functional groups on the surface, due to strong spin-orbit coupling efficiently producing triplet excitons via CIS. Doping with heteroatoms such as N, P and halogens further favors n*^n transitions in these groups, increasing the proportion of triplet excitons (DENG et al., 2013a; JIANG et al., 2017, 2018a; LI et al., 2016; TAN et al., 2016; TU et al., 2019a). However, due to the instability of phosphorescence under ambient conditions, it is necessary to use certain matrices (e.g., polyvinyl alcohol (PVA), polyurethane, urea / biuret, or zeolites) along with the CDs to stabilize and immobilize the species that produce the triplet excitons Ti in order to enable... Petition 870250065394, dated 07 / 29 / 2025, p. 7 / 46 5 / 30 Ti^So radiative transitions (DENG et al., 2013a; JIANG et al., 2017, 2020b; LI et al., 2019; LIU et al., 2017; TAN et al., 2016).

[009] Deng and colleagues (2013) first demonstrated FTA in CDs obtained from the pyrolysis of the disodium salt of ethylenediaminetetraacetic acid (Na2EDTA) and incorporated into a PVA matrix with a phosphorescence lifetime of 380 ms. FTA in this work was achieved by the presence of the C=O bond in aromatic rings, favoring spin-orbit coupling. The importance of the PVA matrix was confirmed when comparing the phosphorescence emission of these CDs dispersed in water and in other polymeric matrices, such as cellulose and polyethylene glycol (20,000). This matrix acts in the formation of networks stabilized by hydrogen bonds between the hydroxyl groups of PVA and the carboxylic groups on the surface of the CDs, preventing the non-radiative deactivation of their T1 states. Furthermore, oxygen is a strong suppressor of triplet state emission, while PVA has a good oxygen barrier performance.Therefore, according to Deng, another possible role of PVA would be to effectively prevent direct collisions between aromatic carbonyls and oxygen molecules, thus promoting phosphorescence (DENG et al., 2013b). More recent studies show matrix-immobilized CDs with quite remarkable FTA (GAO et al., 2018; JIANG et al., 2018a; TAO et al., 2018; ZHU et al., 2019). However, in all cases, FTA is always associated with the formation of hydrogen bonds.

[010] It has been observed that, to exhibit FTA, matrices containing CO and / or CN groups, on the one hand, can form excited triplet states through intersystem crossing (CIS) due to their strong spin-orbit coupling and, on the other hand, can form hydrogen bonds between O or N elements and the matrices. Thus, the formation of hydrogen bonds is fundamental to achieving FTA from CDs, as it suppresses non-radiative relaxations of excited triplet species (JIANG et al., 2020b).

[011] In general, works using CDs present five authentication methods to prevent counterfeiting: i) Smartphone-based authentication, where CDs can be designed to interact with smartphone applications. Petition 870250065394, dated 07 / 29 / 2025, p. 8 / 46 6 / 30 equipped with specific detection technologies, allowing consumers or authorities to authenticate products using widely available devices; ii) Embedding in materials, where CDs can be integrated into the product material, adding an extra layer of security. For example, they can be embedded in polymers, fabrics, or other materials to create a unique and difficult-to-replicate identifier; iii) Authentication labels, where CDs can be embedded in labels, tags, or packaging materials containing unique patterns or information that can only be verified using specialized devices, making counterfeiting difficult; iv) Optical properties for authentication, where the optical properties of CDs, such as fluorescence, can be leveraged for authentication.Authentic products may emit certain luminescent patterns visible under specific conditions, facilitating reliable verification; v) Responses to temperature or environment, where CDs may react to changes in temperature or other environmental conditions, exhibiting alterations that indicate authenticity or exposure to inappropriate factors (SIMÕES et al., 2024).

[012] In addition, recent studies on information encoding using CDs highlight three main data encoding methods: i) Steganography and invisible ink, where CDs can be used in steganography, which is the practice of hiding information within other physical objects or messages to avoid detection, concealing information within other data or creating invisible inks. The unique optical properties of CDs allow the encoding of hidden messages that are only revealed under specific conditions, adding a layer of security to the transmitted information; ii) Biocompatible security markers: CDs are often biocompatible, and this property can be used in the secure marking of documents or labels.They can be invisible to the human eye and detectable using specific tools, contributing to document authentication; iii) Sensors for environmental conditions, where CDs can be sensitive to changes in environmental conditions. Incorporating CDs into sensors that respond to specific stimuli (such as... Petition 870250065394, dated 07 / 29 / 2025, page 9 / 46 7 / 30 temperature, pH or light) can be part of a multi-level security system, where information is revealed only under controlled conditions (SIMÕES et al., 2024).

[013] Recently, the development of new nanostructured products based on CDs with FTA presents itself as an opportunity for advances in information security. Thus, combining CDs and data encryption can result in the creation of an efficient platform to combat the falsification of information or products.

[014] Given the above, it is established that up to the present moment the use of CDs with ambient temperature phosphorescence sensitive to humidity, as ink for printing coded information, has not been described. Summary

[015] The present invention presents a new, simple, efficient data encoding platform using a type of easily synthesized, low-toxicity, low-cost, O, N, and P-doped Carbon Dot with multiple tunable emissions, especially moisture-sensitive room temperature phosphorescence (FTA). Furthermore, it possesses considerable quantum yield and sensitivity to different pHs. Therefore, the synthesized material and product of this invention acts as a photoluminescent security device for data encoding through deposition on surfaces by inkjet printing. The moisture-sensitive FTA provides an additional level of security for labels and tags with unique codes that can only be identified by changes in humidity on the printed label or in the environment.

[016] Initially, the invention describes the methods used for the synthesis and characterization of moisture-sensitive FTA CDs (FTASU-CDs). To this end, FTASU-CDs were first obtained through synthesis assisted by a domestic microwave. Subsequently, printing inks were prepared at various concentrations to verify the best application conditions. The chemical and morphological characterizations of the FTASU-CDs were carried out through Petition 870250065394, dated 07 / 29 / 2025, page 10 / 46 8 / 30 of the absorption spectroscopy techniques in the ultraviolet and visible region (UVVis), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and photoluminescence spectroscopy.

[017] In a second aspect, the present invention describes a methodology that makes use of CDs-FTASU, for which there are no precedents of use as a single data encoding platform with multilevel security through multiple moisture-sensitive phosphorescence emission and tunable according to excitation length.

[018] In another aspect, CDs-FTASU exhibit sensitivity in absorption and emission according to different pH conditions, making it another promising level in the production of food packaging labels, as indicators of contamination or expiration dates of perishable foods.

[019] The term “Carbon Dots (CDs)” refers to carbon-based nanoparticles, considered a new generation of luminescent nanomaterials that have received considerable attention due to their unique and excellent optical light-emitting properties (LIM; SHEN; GAO, 2015; XU et al., 2004). In addition to their environmentally friendly nature, CDs also exhibit chemical inertness, low toxicity (HUANG et al., 2013), emission control (PARK et al., 2020), and excellent stability, sparking interest in various research fields. CDs are nanoparticles composed mainly of carbon, with diameters between 1 and 10 nm, which can exhibit fluorescent and phosphorescent emission, generally dependent on the excitation wavelength.

[020] By the term “phosphorescence” we mean a type of emission that has been widely used as a security device in various fields, from authenticating money to protecting pharmaceutical products. This is because phosphorescence can be easily detected in low light conditions, making it a powerful tool for identifying authentic products in dark environments. Finally, the ability of materials to emit light in different modes opens up possibilities for creating more secure security codes. Petition 870250065394, dated 07 / 29 / 2025, page 11 / 46 9 / 30 complex and difficult to reproduce, offering greater protection against product counterfeiting and piracy (JIANG et al., 2016; MILLER; REICHSTEIN; MANDEL, 2022).

[021] The term “anti-counterfeiting” refers to a set of techniques and technologies used to guarantee the authenticity of products or documents, making their unauthorized reproduction difficult. Its main objective is to prevent fraud and protect brands, consumers, and systems from possible counterfeits. Examples include security labels, holograms, unique codes, and dynamic properties such as sensors that react to light or temperature. These solutions allow for the identification of genuine items from imitations or illegitimate copies.

[022] The term “data encoding” refers to the process of transforming information into a protected format, making it unreadable or inaccessible without a key or appropriate authorization. The goal is to ensure the security, confidentiality, and integrity of the data, protecting it against unauthorized access. Methods include cryptography (such as AES and RSA) and steganography.

[023] The term “Steganography” refers to the technique of concealing information within other media, such as texts, images, videos, or audio, in such a way that its presence is not perceived. Unlike cryptography, which protects the content of the message, steganography aims to hide its existence. Methods include modifying pixels in an image or altering audio bits. It is used in secret communications, digital watermarks, and intellectual property protection, but it can also be exploited in malicious practices. Problems and limitations of the state of the art

[024] Conventional luminescent inks for encoding information typically have high production and application costs, contain toxic components in their composition, degrade with exposure to UV light, heat or humidity, and have limited visibility, requiring specific equipment for Petition 870250065394, dated 07 / 29 / 2025, page 12 / 46 10 / 30 verification. Furthermore, the technical complexity in application, compatibility issues with certain materials, and detection difficulties hinder unique signatures. These limitations highlight the need to combine them with other, more effective security technologies or to develop unique signature materials with multiple security levels.

[025] Currently, there are many challenges to be faced in combating product and information counterfeiting, including the advanced reproduction of security technologies, including the high cost associated with developing effective anti-counterfeiting methods. In this context, steganography emerges as a promising technique, allowing the concealment of information in discreet media, such as images and documents, making its detection by counterfeiters more difficult. However, its application requires constant innovation to avoid vulnerabilities and ensure the authenticity of the protected data.

[026] In view of this, the invention described in the present patent proposes the use of inks for jet printing, based on carbon nanoparticles (Carbon Dots) that exhibit phosphorescence at room temperature sensitive to humidity, with tunable multi-emission according to the excitation wavelength, in conjunction with steganography techniques for encoding information in images and documents. Advantages of the invention

[027] The use of the present invention as a unique data encoding platform with multi-level security through multiple tunable phosphorescence emission according to excitation length and absence of humidity brings the following essential advantages: 1) The methodology for preparing CDs-FTASU inks consists of a simple and viable method from an experimental and economic point of view; 2) CDs-FTASU-based inks exhibit low cytotoxicity, according to test results in brine shrimp; Petition 870250065394, dated 07 / 29 / 2025, page 13 / 46 11 / 30 3) The CDs developed and printed with inks are sensitive to pH variations; 4) The CDs developed and printed with inks exhibit phosphorescence with sensitivity to humidity; 5) The developed inks exhibit multiple phosphorescence emissions that can be tunable according to the excitation wavelength; 6) The CDs developed and printed with inks are sensitive to pH variations; 7) Inks developed from CDs with ambient temperature phosphorescence sensitive to humidity showed very promising results in encoding information using the steganography technique, with the aid of an inkjet printer. The novelty and the technical effect achieved [0 28] The advance achieved with this invention consists in the fact that until now no research institution, teaching institution or private sector has employed CDs with pH-sensitive fluorescence and humidity- and temperature-sensitive ambient temperature phosphorescence as a single data encoding platform, and with multilevel security through multiple tunable phosphorescence emission according to excitation length and absence of humidity. Brief description of the Figures [0 29] Fig. 1 shows (a) UV-Vis spectra of the carbon dot suspension at room temperature (295 K), at pH 6 and with a 200x dilution (800 ppm) varying the reaction time and (b) maximum absorption intensities at different reaction times. [03 0] Fig. 2 shows transmission electron microscopy images (a) micrograph showing the uniformity of particle sizes in Petition 870250065394, dated 07 / 29 / 2025, page 14 / 46 12 / 30 set with a histogram (insert) and (b) micrograph showing the crystalline and amorphous regions of CDs-FTASU, including the crystallographic planes. [03 1] Fig. 3 shows the FTIR spectrum of the CDs-FTASU. [03 2] Fig. 4 shows spectra in the UV-Vis region showing the effect of pH on the absorbance of CDs-FTASU in aqueous suspension. [03 3] Fig. 5 shows the emission spectra (λEχ = 350nm) of the CDs-FTASU suspension at different pH and (b) maximum emission intensity as a function of pH. [03 4] Fig. 6 shows the cytotoxicity tests of CDs-FTASU in Artemia salina L. larvae. [03 5] Fig. 7 shows the excitation (a) and emission (b) spectra of aqueous solutions of CDs-FTASU, obtained with different reaction times, at room temperature (295 K), at pH 6 and with a dilution of 200x. [03 6] Fig. 8 shows the absolute quantum yield of the CDs-FTASU suspension (800ppm) using the integrating sphere. [03 7] Fig. 9 shows the dependence of the emission spectra of aqueous solutions of CDs-FTASU at pH 4, 6, 8 and 10, with excitation. [03 8] Fig. 10 shows the (a) Excitation (λEm = 430 nm) and (b) Emission (XEx = 280 and 350 nm) spectra of solid-state CDs-FTASU at room temperature (295K) [03 9] Fig. 11 shows the time-resolved phosphorescence spectra: Excitation (a) and Emission (b) of CDs-FTASU, in the solid state at room temperature (295K), at pH 6 and with a dilution of 200x (800ppm). Petition 870250065394, dated 07 / 29 / 2025, page 15 / 46 13 / 30 [04 0] Fig. 12 shows the time-resolved phosphorescence spectra: excitation (a) and emission (b) of CDs-FTASU at cryogenic temperature (77 K), pH 6 and 200x dilution (800 ppm). [04 1] Fig. 13 shows a sequence of photographs of a capillary containing a suspension of CDs-FTASU immersed in liquid N2, under excitation at 350 (a) and 280 nm (b) - first images in each figure - and after switching off the excitation - sequence of images after the first. [04 2] Fig. 14 shows chromaticity diagrams and color coordinates obtained from the steady-state and time-resolved emission spectra of the CDs-FTASU suspension at cryogenic temperature, using. [04 3] Fig. 15 shows (a) images of CDs-FTASU printed on tracing paper, containing blue fluorescence emission (λEχ = 365 nm) and (b) an image of CDs-FTASU printed on tracing paper, containing green phosphorescence emission. [04 4] Fig. 16 shows fluorescence spectra (λEx = 360 nm) of the tracing paper and the printout with CDs-FTASU (a). Phosphorescence spectrum of the printout after excitation at 360 nm. Both analyses were performed as soon as the printouts were removed from the oven and cooled to room temperature.

[045] Fig. 17 shows FTIR spectra of the CDs-FTASU pellet in KBr, with humidity from exposure to air (I) and after 45 min of heating in an oven at 80 °C (II). Detailed description of the invention Example 1. Preparation and characterization of room temperature phosphorescent carbon dot ink sensitive to humidity (CDs-FTASU) Petition 870250065394, dated 07 / 29 / 2025, page 16 / 46 14 / 30 Example 1.1. Synthesis of FTASU-CDs

[046] CDs-FTASU were obtained from ethanolamine and phosphoric acid using microwave-assisted synthesis, according to the protocol described by Jiang et al. (2018). In a borosilicate reactor, 4 mL of ethanolamine, 16 mL of deionized water, and 8 mL of 85% PA orthophosphoric acid were added and the mixture was homogenized. This mixture was then subjected to microwave radiation for time intervals of 1 to 3 min, using maximum power (800 W). 100 mL of deionized water were added to the obtained material, and the pH was adjusted to 6 with a sodium carbonate solution (1 mol. L-1). The suspension was centrifuged for 10 min at a rotation frequency of 5400 rpm and then filtered with a millipore membrane (0.22 mm). To obtain the CDs-FTASU in the solid state, the suspension was heated to 100 °C on a hot plate until the water completely evaporated. Example 1.2. Preparation of printing inks

[047] The CD-based printing inks were prepared in an aqueous medium. The pH of the CD stock suspension was adjusted to pH 6, and different dilutions were made with deionized water (100, 75, 50, and 25%). These solutions were added to a previously manufactured cartridge, where the cap was removed, the original sponges and inks were taken out, and, with the aid of a Büchner funnel and a vacuum pump, it was washed thoroughly with deionized water until no traces of the original ink remained. After washing, new sponges were added, and then the security ink was added.

[048] The CD ink prints were made on A4 size tracing paper on a commercial inkjet printer, with a resolution of 1200 x 1200 dpi in a single print cycle, varying the degree of color saturation in GIMP 2.10.24 software. Although the solvent is water, the print dries quickly due to the small volume of ink deposited (2 - 10 pL). Petition 870250065394, dated 07 / 29 / 2025, page 17 / 46 15 / 30 Example 1.3. Characterization methods and characteristics of FTASU CDs

[049] To investigate the composition of the CDs-FTASU produced according to the procedure described in Example 1.1, the electronic transitions, as well as some properties of the produced CDs-FTASU, were evaluated through the electronic absorption spectra in the UV-Vis (800 - 200 nm) obtained in a Shimadzu Cary-60 spectrophotometer.

[050] To verify the influence of humidity on the vibrational band profile of the material in the solid state, Fourier Transform Infrared Spectroscopy (FTIR) analyses were performed. Pellets of lyophilized CDs-FTASU in a potassium bromide (KBr) matrix were prepared and readings were taken every 2 cm⁻¹ with 64 scans, in the range of 4000 to 400 cm⁻¹. After this reading, the pellet was placed in an oven at 80 °C for 45 min to remove any moisture, and subsequently a new reading was taken under the same conditions. The equipment used was a Shimadzu IR tracer-100.

[051] Morphological and structural characteristics were investigated by transmission electron microscopy (TEM) using a Thermo Scientific Jeol JEM2100 microscope. The sample for transmission imaging was prepared using a diluted suspension (200x from the initial suspension) and placed on a polymer screen (formavar) along with a carbon layer.

[052] The photoluminescence properties (excitation, emission, and lifetime spectra) of CDs were investigated in aqueous suspension using a Jobin-Yvon Fluorolog-3 spectrofluorometer (Horiba, Japan) equipped with continuous (450 W xenon lamps) and pulsed (150 W xenon lamps) excitation sources, and a Hamamatsu R928P photomultiplier. Data were collected at a 90° angle to the excitation beam, at room temperature and 77 K. For the low-temperature (77 K) measurements, a quartz capillary was used, to which the 800 ppm CD suspension was added. This capillary was positioned in the center of a cylindrical quartz tube (cold finger) containing liquid nitrogen, and aligned with the excitation beam and the detector. The increments for measuring fluorescence were Petition 870250065394, dated 07 / 29 / 2025, page 18 / 46 16 / 30 of 1.0 nm, the integration times were 0.1 if the excitation and emission slits were 3 nm. The absolute quantum yield was determined using a Quanta-phy integrating sphere, obtained from Horiba Scientific.

[053] The fluorescence lifetime was obtained using a nano LED as an excitation source at 339 nm. For the phosphorescence lifetime, both at room temperature and 77 K, two approaches were used: i) using a continuous lamp as an excitation source in kinetic mode. In this mode, the intensity of the maximum emission was monitored every 20 seconds after the excitation source was switched off. The total data acquisition time was 120 s. ii) using a pulsed lamp, with a sample window of 500.00, time per flash of 10500.01, flash count of 1. The entire phosphorescence lifetime was measured with a 10 nm slit.

[054] The luminescent prints were characterized by luminescence spectroscopy. To evaluate the influence of humidity on the emission of the prints, they were dried under ambient conditions before analysis. Then, they were placed in an oven at 80 °C for 10 min and the measurements were repeated.

[055] The influence of pH on absorbance and luminescence was investigated in aqueous suspension with a 200x dilution, relative to the synthesis concentration, in the pH range 3 - 10. To correct the pH, sodium hydroxide solutions at concentrations of 0.1 and 1.0 mol. L'1 were used.

[056] Fig. 1 shows the UV-Vis spectra for the CDs, where it is possible to observe that the absorption spectral profiles undergo profound changes with reaction time. Initially, up to 1.5 min, a band centered at 270 nm is formed (black and red lines). As the reaction progresses, from 2.0 to 2.5 min, two bands are observed between 300 and 400 nm. For the system formed after 3.0 min of irradiation, in this range of 200 to 250 nm, two bands appear (Fig. 1a). According to literature reports, the absorption band between 250 and 300 nm can be associated with π-π* transitions of sp2 aromatic domains of the carbogenic nucleus (JIANG, et al., 2018; DING, et al., 2020). In turn, the band with a maximum at 330 nm is related to n-π* electronic transitions involving surface states. Petition 870250065394, dated 07 / 29 / 2025, page 19 / 46 17 / 30 compounds with -C=N and -C=O bonds (JIANG, et al., 2020; LI, et al., 2018; JIANG, et al., 2018). The electronic transitions observed below 250 nm have not yet been adequately investigated, but we believe they may originate from π-π* transitions of sp2 aromatic domains of carbogenic nuclei of different sizes. Among the five systems analyzed, the system with a 2.5 min reaction time showed the highest absorbance for the bands between 250 and 300 nm, and 300 to 400 nm (Fig. 1b). This may indicate that the concentration of CDs-FTASU is higher in this system and that this should be the best synthesis condition. However, other parameters should be analyzed, such as the emission intensity.

[057] In the high-resolution transmission electron microscopy images (Fig. 2a), well-dispersed spherical particles with average sizes of 3.99 ± 0.13 nm can be observed. Fig. 2b shows the crystallographic planes with an interplanar distance of 0.21 nm, thus being attributed to the graphitic plane (001), as well as an amorphous region being identified. The average size and interplanar distance were estimated using ImageJ software.

[058] The FTIR spectrum in Fig. 3 shows the presence of characteristic bands from the formation of O, N, and P-doped CDs-FTASU. Ethanolamine acts as the main source of amine and hydroxyl groups, and phosphoric acid acts as the main source of phosphate groups on the surface of the material. The bands located at 1715, 1650, 1558, and 1253 cm⁻¹ indicate the existence of -C=O, -C=N, -N=O, and P=O / CN groups, respectively. The spectrum exhibits a broad band between 2500-3750 cm⁻¹, containing distinguishable peaks at 3380, 3232, 3016, and 2821 cm⁻¹, resulting from the stretching vibrations of OH bonds, -NH₂, and -CH₂ groups. The band at 1647 cm⁻¹ corresponds to the NH vibration or C=N stretching vibration. The bands at 1440, 1253, 1087, and 1008 cm⁻¹ can be attributed to bending vibration of CH, stretching vibrations of P=O / CN, CO / PO, and PN bonds, respectively.Finally, the bands at 2411 and 524 cm-1 imply the presence of amino and phosphate groups, respectively, which indicates good dispersion of CDs-FTASU in water (JIANG et al., 2018b; PAVIA et al., 2010; TU et al., 2019b). Petition 870250065394, dated 07 / 29 / 2025, page 20 / 46 18 / 30 Example 2 - Effect of pH on the absorption and fluorescence of FTASU-CDs in aqueous suspension Example 2.1. Effect of pH on absorption

[059] As mentioned above, the optical properties of CDs are usually pH dependent. Therefore, we initially investigated the dependence of the absorption of the aqueous suspension of CDs on pH variation, in the range of 3 to 10. The absorption spectra (Fig. 4) exhibit the same spectral profile up to pH = 9, showing only changes in absorbances. Initially, there is an increase in absorbance at pH = 3, and then a progressive decrease with increasing pH. This increase with a one-unit change in pH needs to be further verified to rule out possible operational effects. Furthermore, the decrease in absorbance with increasing pH may be attributed to the loss of stability of the suspension, leading to particle aggregation. For the system at pH = 10, a change in the spectral profile is observed in the absorption band between 300 and 400 nm.We can observe that the band with a maximum at 330 nm exhibits a slight decrease in absorbance with increasing pH, and the band with a maximum at 265 nm exhibits an increase in absorption intensity from pH 3 to 4, which gradually decreases until pH 7, remaining stable until pH 10. This behavior also needs further investigation; however, it can be inferred that it is an effect of the formation of aggregates in suspension. Example 2.1. Effect of pH on the fluorescence of CDs in aqueous suspension

[060] Fig. 5 shows the fluorescence response of the aqueous CDsFTASU suspension with pH. As the pH increases, the luminescence intensity decreases, as verified in the absorption spectra. As mentioned earlier, this occurs due to deprotonation of surface groups and loss of stability of the suspension. It is worth noting that the decrease in absorbance, observed between pH 3 and 4, did not affect the emission intensity. Another effect related to the decrease in emission intensity is the increase of OH (which are more efficient luminescence suppressors) in the medium, which favors the non-radiative deactivation of Petition 870250065394, dated 07 / 29 / 2025, page 21 / 46 19 / 30 Multiphonon deactivation luminescence involves high-energy vibrations of solvent molecules. NH oscillators also contribute to luminescence suppression, although to a lesser extent. Example 3 - Cytotoxicity of printing ink based on CDs-FTASU

[061] The CDs-FTASU-based printing ink was subjected to a cytotoxicity test in Artemia larvae. For this, Artemia salina L. (Artemiidae) eggs were acquired and placed to hatch in saline solution at a temperature of 25 °C, with plenty of light. After this time, 10 ± 1 larvae were added to each sterile vial containing saline solutions with CDs-FTASU at concentrations of 100 - 2500 ppm, in triplicate, for 24h.

[062] Thus, the results showed that the synthesized ink exhibits low toxicity when applied to Artemia salina Leach larvae (Artemiidae), which is an invertebrate widely used in alternative tests to determine the toxicity of natural chemicals, due to its low cost and good commercial availability, in addition to having a good correlation (r = 0.85 p < 0.05) with “in vivo” and “in vitro” studies [(A. LAGARTO PARRA, 2001)]. In this study, the Median Lethal Doses (LD50 value) for CDs-FTASU were 786.44 pg / mL, a value obtained 24 hours after ingestion of CDs-FTASU by the Artemia larvae (Fig. 6). According to Meyer (1982), when the LD50 values ​​(A. LAGARTO PARRA, 2001; MAYARA et al., 2015; MEYER et al., 1982) for a given material are between 500 and 1000 pg / mL, this material has low toxicity. Example 3 - Photoluminescent properties of CDs-FTASU based paints in aqueous medium Example 3.1.

[063] The good dispersion of CDs-FTASU in water facilitated measurements of the suspended material, thus allowing greater control over the concentration of the obtained material. Spectra of the CDs-FTASU obtained at different synthesis times (1-3 min) were obtained, maintaining a dilution factor of 200x. Petition 870250065394, dated 07 / 29 / 2025, page 22 / 46 20 / 30 all samples. This dilution was necessary because the emission intensities of some solutions of the materials obtained saturated the detector at the synthesis concentration.

[064] The excitation spectra, monitoring the emission at 420 nm, of the CDs-FTASU at different reaction times (Fig. 7a) exhibit a broad band between 275 and 400 nm, with a maximum at 355 nm. This broad band can be attributed to S1 ^ S0 transitions, related to surface states, as observed in the absorption spectra for these same systems. However, bands related to transitions involving the carbogenic nuclei were also observed. This behavior indicates that surface states are primarily responsible for the photoluminescence of the synthesized CDs-FTASU.

[065] The emission spectra (λEx = 355 nm) of the CDs-FTASU solutions with different synthesis times (Fig. 7b) exhibit a broad fluorescence band, with a maximum at 420 nm. This broad band is characteristic of materials that have many surface defects. It can be observed that the emission intensity increases abruptly (~38x) when the synthesis time increases from 2 to 2.5 min. Another point to highlight is the decrease in the emission intensity of the suspension of the material obtained with 3 min of synthesis, when compared to the emission intensity of the suspension obtained with 2.5 min.

[066] The quantum yield of fluorescence (ΦF) is the ratio between the number of photons emitted by fluorescence and the number of photons absorbed (equation 1). Thus, ΦF is related to the probability of the excited state being deactivated by fluorescence and not by other non-radiative deactivation processes such as internal conversion and vibrational relaxation (ZHU et al., [n.d.]). , number of photons emitted Φγ = ---—---— number of photons absorbed

[067] The absolute quantum yield obtained for the aqueous suspension of CDs-FTASU at pH 6, with excitation at 355 nm, was ΦF = 11.83% (±0.09) (Fig. 8). Therefore, it can be observed that the absolute ΦF obtained is within the expected range for Petition 870250065394, dated 07 / 29 / 2025, page 23 / 46 21 / 30 of this type of material. This yield is quite considerable for materials with potential applications in data encoding.

[068] The effect of wavelength on excitation in the fluorescence of the CDs-FTASU ink suspension was evaluated in the range of 250 to 490 nm (Fig. 9). We can observe that the emission spectral profiles do not change as the excitation wavelength varies from 250 to 330 nm. Only an increase in emission intensity and a better definition of the band are observed. From 350 nm onwards, the emission maximum shifts proportionally to the variation in excitation wavelength. This behavior is typical of molecular systems and systems whose fluorescence involves surface states, where the Stokes shift is relatively constant. This behavior also suggests the absence of distinct particle fractions with different diameters whose luminescence can be tuned through the excitation wavelength. This aspect will be discussed in more detail during the investigations of the spectroscopic properties of the synthesized CDsFTASU.On the other hand, the large bandwidth is characteristic of fluorescent carbon dots, due to the inhomogeneity in the particle structure, since there are different functional groups distributed along the surface (such as OH, -C=O, -NH2) (ZHU et al., 2015). Furthermore, the spectra shown in Fig. 9 also show that the dependence of luminescence on excitation is independent of pH. Example 4 - Characterizations and photoluminescent properties of CDs-FTASU-based inks in solid state and printed on paper.

[069] The emission spectra (Fig. 10b) of the CDs-FTASU ink, in the solid state, exhibit the same profile observed for suspension. On the other hand, the excitation spectrum shows significant changes, both for the excitation maximum and the spectral profile (number of bands and width at half-height). The excitation maximum was shifted to 330 nm and there is a second excitation band, of low intensity, at 280 nm, superimposed on the main band. Probably due to this Petition 870250065394, dated 07 / 29 / 2025, page 24 / 46 22 / 30 large overlap, no significant changes were observed in the emission spectral profile.

[070] In addition to intense fluorescence, the synthesized CDs-FTASU exhibited strong phosphorescence emission in the solid state, at room temperature and free of moisture. The phosphorescence spectrum obtained after excitation at 250 nm (red line in Fig. 11b) shows two bands, one of lower intensity in the blue (λMax = 430 nm), and another in the green (λMax = 500 nm). Phosphorescence is favored in the solid state due to the decrease in non-radiative deactivations related to collisions with solvent molecules and molecular vibrations. From these results, excitation spectra were obtained by monitoring the phosphorescences at the maxima of these two bands.

[071] The two excitation spectra (Fig. 11a) exhibit very distinct spectral profiles. The spectrum obtained by monitoring phosphorescence at 500 nm shows two overlapping bands with maxima at 280 and 370 nm (excitation maximum of the spectrum). The spectrum obtained by monitoring phosphorescence at 430 nm also shows two emission bands, however, with relative intensities inversely proportional to those obtained by monitoring phosphorescence at 500 nm. These results suggest that the two phosphorescence bands of the material are relatively independent and the spectral profile can be modulated from the excitation.

[072] To verify this hypothesis, the phosphorescence spectrum was obtained after excitation at 280 nm (black line in Fig. 11b). As expected, this phosphorescence spectrum shows a significant change in the relative intensities of the phosphorescence bands already observed after excitation at 350 nm. Since two independent bands were not observed in the fluorescence study of CDs-FTASU, we ruled out the possibility that these two phosphorescence bands result from the coexistence of two groups of particles with different diameters. As evidenced by high-resolution transmission electron microscopy analysis, the CDs-FTASU particles have a paracrystalline carbon structure with sp2 carbogenic nuclei. The emission from carbogenic nuclei shows Petition 870250065394, dated 07 / 29 / 2025, page 25 / 46 23 / 30 lower intensity than the emission originating from surface states, mainly fluorescence. Thus, we attribute the phosphorescence in the blue to Ti > So transitions of the carbogenic nuclei and the phosphorescence in the green to Ti > So transitions related to surface states in the same particle. This is the first report of multiple phosphorescence emission, at room temperature, in CDs.

[073] In order to make the multiple tunable phosphorescence emission more evident with only a change in excitation wavelength, experiments were carried out at low temperature with the aid of liquid nitrogen (77K). As observed for the phosphorescence excitation spectrum in the solid state, monitoring the emission at 500 nm, the excitation spectral profile of the phosphorescence in the CDs-FTASU suspension at 77 K exhibits two bands, with maxima at 280 and 350 nm (Fig. 12a). However, the intensity of the band at 280 nm is much more intense than that observed in the phosphorescence excitation spectrum in the solid state. An even more expressive change is observed for the phosphorescence excitation spectrum at 77 K when the emission is monitored at 430 nm. In this case, the excitation spectrum is composed almost entirely of the band with a maximum at 280 nm.This causes the modulation of emission by excitation in the time-resolved regime to be even more pronounced at cryogenic temperature than in the solid state. Thus, we conclude that there is a non-radiative deactivation channel, or channels, of phosphorescence in CDs-FTASU synthesized at room temperature, and this channel(s) is / are highly temperature-dependent, especially the phosphorescence originating from sp2 carbogenic nuclei. Another conclusion we can reach is that phosphorescence becomes the main luminescence mechanism of CDs-FTASU at cryogenic temperature, even in the steady-state regime.

[074] Thus, the results were even more significant and it was possible to easily capture the multi-emissible phosphorescence effect with a common cell phone camera. The first images in Fig. 13 show the suspension luminescences of CDs-FTASU in a capillary immersed in liquid N2, under excitation at 350 (a) and 280 nm (b). Based on the results presented, it was already expected that the Petition 870250065394, dated 07 / 29 / 2025, page 26 / 46 24 / 30 The suspension exhibited a blue photoluminescence color, with color coordinates (x, y), based on the 1983 CIE system, (0.196; 0.368) and (0.215; 0.318), respectively for excitation at 280 and 350 nm (Fig. 14). After the excitation was turned off, the suspension exhibited different photoluminescence colors for each excitation. When the excitation at 350 nm was turned off, the capillary exhibited a green photoluminescence color. On the other hand, when the excitation at 280 nm was turned off, the capillary continued to exhibit a blue photoluminescence color.

[075] The unique optical properties exhibited by the synthesized CDs-FTASU, with excitation-modulated phosphorescence spectral signature, motivated us to produce luminescent prints with this system. The modulable phosphorescence spectral signature of CDs-FTASU, in the solid state, presents great potential for use as a highly forgery-resistant luminescent barcode. The high affinity of CDs-FTASU for water reduces the costs of security ink production, facilitates processability, and allows manipulation of ink viscosity by mixing with more viscous solvents such as ethylene glycol. This allows CDs-FTASU to be used in printers with different actuators for material deposition. The high stability in water reveals the environmentally friendly nature of the developed technology.

[076] As described in the experimental section, after depositing the aqueous suspension of CDs-FTASU onto tracing paper, the print was dried at room temperature. Immediately after drying, the print was exposed to UV light (365 nm), exhibiting blue fluorescence (Fig. 15b). Upon switching off the lamp, the material displayed the same printed image, but with a green photoluminescent color (Fig. 15c). To our surprise, after a few seconds, the green phosphorescence was no longer observed. However, upon reheating in the oven, the print again exhibited phosphorescence. By verifying the repetition of this on / off switching of phosphorescence mediated by heating, we identified that, while heated, the print does not exhibit phosphorescence and, as soon as the print cools, the phosphorescence reappears. However, upon reabsorbing moisture from the air. Petition 870250065394, dated 07 / 29 / 2025, page 27 / 46 At 25 / 30 atmospheric pressure, the phosphorescence disappears again. This behavior suggests that the activation of phosphorescence may be related to the hydration of CDs-FTASU. This test was performed at various times and with several repetitions, and we did not reach a point where the On / Off switching of phosphorescence was exhausted.

[077] We analyzed the photoluminescent properties of the dry prints, excited at 365 nm, which is a typical excitation provided by common UV lamps. The tracing paper exhibits an intrinsic blue fluorescence; however, the printed CDs-FTASU confers a more pronounced fluorescence intensity (Fig. 16a), making the printed region easily visible to the naked eye. Despite the paper's fluorescence background, the fluorescence spectral profile exhibited by the print is little influenced, more closely resembling the fluorescence spectral profile of CDs-FTASU in the solid state. On the other hand, the phosphorescence spectral profile shows no influence from the background light originating from the tracing paper. Thus, the observed phosphorescence spectral profile (Fig. 16b) is identical to the phosphorescence profile of CDs-FTASU in the solid state when excited at 350 nm.As observed for CDs-FTASU in the solid state, CDsFTASU prints exhibit phosphorescence originating from carbogenic cores and partially overlapping surface states.

[078] In addition, in order to verify the influence of water on the surface functional groups of CDs-FTASU, CDs-FTASU powder was pelletized in a KBr matrix and exposed to moisture. When subjected to a UV lamp (λEχ = 365 nm), this pellet showed only blue fluorescence emission, without phosphorescence. On the other hand, after drying in the oven, the material also began to show phosphorescence emission. Thus, we can associate the decrease in intensities in other bands, between 1,000 and 1,300 cm⁻¹, with the formation of inter- and intraparticle hydrogen bonds through the surface functional groups of CDs-FTASU, as shown in Fig. 17. These interactions restrict some vibrational modes and increase the intersystem crossing rate, favoring phosphorescence emission. This phenomenon can be reversed as the exposure increases. Petition 870250065394, dated 07 / 29 / 2025, page 28 / 46 26 / 30 printed in the atmosphere, rich in moisture, and thus phosphorescence is inhibited. This highly hygroscopic character of CDs-FTASU is related to the high concentration of oxygenated functional groups, capable of forming, mainly, hydrogen bonds and capturing water molecules present in the air.

[079] With this, images of the BSTR laboratory and UFPE logos were printed on a conventional inkjet printer, and this CDsFTASU-based ink showed only fluorescence emission in the presence of moisture, and immediately after the moisture was removed, with the aid of temperature or high vacuum, the presence of green phosphorescence could be observed with the naked eye or a cell phone camera, as shown in Fig. 15. But at the level of photoluminescence spectroscopy, the presence of another blue phosphorescence emission can be observed when excited at λEx = 365 nm, and becomes more evident when excitation occurs at λEx = 365 nm. This property provides a unique coding for this type of material, being quite promising in file security. Finally, this material becomes quite promising in the security of packaging and products of high commercial value.Furthermore, CDs with moisture-sensitive phosphorescence are a material with great potential for use in information encoding, as they give printed material a unique and difficult-to-clone identity. Another possible application to be explored is moisture detection by luminescence. References [08 0] A. LAGARTO PARRA. Comparative study of the assay of Artemia salina L. and the estimate of the medium lethal dose (LD50 value) in mice, to determine oral acute toxicity of plant extracts. Phytomedicine, 2001. [08 1] ARPPE-TABBARA, R.; TABBARA, M.; S0RENSEN, TJ Versatile and Validated Optical Authentication System Based on Physical Unclonable Functions. ACS Applied Materials and Interfaces, 2019. [08 2] CAI, S. et al. Enhancing Ultralong Organic Phosphorescence by Effective π-Type Halogen Bonding. Advanced Functional Materials, vol. 28, no. 9, 2018. Petition 870250065394, dated 07 / 29 / 2025, page 29 / 46 27 / 30 [08 3] DENG, Y. et al. Long lifetime pure organic phosphorescence based on water soluble carbon dots. Chemical Communications, v. 49, n. 51, p. 5751-5753, 30 maio 2013 a. [08 4] DUNG, M. X. et al. Tuning the Emission Color of Hydrothermally Synthesized Carbon Quantum Dots by Precursor Engineering. VNU Journal of Science: Natural Sciences and Technology, v. 35, n. 1, 2019. [08 5] FAN, R. J. et al. Photoluminescent carbon dots directly derived from polyethylene glycol and their application for cellular imaging. Carbon, v. 71, 2014. [08 6] GAO, Y. et al. Matrix-Free and Highly Efficient Room-Temperature Phosphorescence of Nitrogen-Doped Carbon Dots. Langmuir, v. 34, n. 43, 2018. [08 7] HAMILTON, W. L. et al. Public health interventions to protect against falsified medicines: A systematic review of international, national and local policies. Health Policy and Planning, 2016. [08 8] HE, Z. et al. White light emission from a single organic molecule with dual phosphorescence at room temperature. Nature Communications, v. 8, n. 1, 2017. [089 ] HOU, J. et al. Facile synthesis of carbon dots in an immiscible system with excitation-independent emission and thermally activated delayed fluorescence. Chemical Communications, v. 51, n. 100, 2015. [090 ] HUANG, X. et al. Effect of injection routes on the biodistribution, clearance, and tumor uptake of carbon dots. ACS Nano, v. 7, n. 7, p. 5684-5693, 23 jul. 2013. [091 ] (ICC), I. C. OF C. THE ECONOMIC IMPACTS OF COUNTERFEITING AND PIRACY Report prepared for BASCAP and INTA. [s.l.] 2017, [s.d.]. Disponível em: <https: / / iccwbo.org / publication / economic-impactscounterfeiting-piracy-report-prepared-bascap-inta / >. [092 ] JIANG, K. et al. Red, Green, and Blue Luminescence by Carbon Dots: Full-Color Emission Tuning and Multicolor Cellular Imaging. Angewandte Chemie, v. 127, n. 18, 2015. [093 ] JIANG, K. et al. Triple-Mode Emission of Carbon Dots: Applications for Advanced Anti-Counterfeiting. Angewandte Chemie, v. 128, n. 25, p. 7347-7351, 13 jun. 2016. [094 ] JIANG, K. et al. Activating Room Temperature Long Afterglow of Carbon Dots via Covalent Fixation. Chemistry of Materials, v. 29, n. 11, 2017. Petição 870250065394, de 29 / 07 / 2025, pág. 30 / 46 28 / 30 [095 ] JIANG, K. et al. Facile, Quick, and Gram-Scale Synthesis of UltralongLifetime Room-Temperature-Phosphorescent Carbon Dots by Microwave Irradiation. Angewandte Chemie, v. 130, n. 21, p. 6324-6328, 22 maio 2018a. [096 ] JIANG, K. et al. Facile, Quick, and Gram-Scale Synthesis of UltralongLifetime Room-Temperature-Phosphorescent Carbon Dots by Microwave Irradiation. Angewandte Chemie, v. 130, n. 21, p. 6324-6328, 22 maio 2018b. [097 ] JIANG, K. et al. Afterglow of carbon dots: Mechanism, strategy and applications. Materials Chemistry FrontiersRoyal Society of Chemistry, , 1 fev. 2020a. [098 ] JIANG, K. et al. Afterglow of carbon dots: mechanism, strategy and applications. Materials Chemistry Frontiers, v. 4, n. 2, p. 386-399, 1 fev. 2020b. [099 ] KATUMO, N. et al. Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication. Scientific Reports, v. 12, n. 1, p. 1-14, 2022a.

[100] KATUMO, N. et al. Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication. Scientific Reports, v. 12, n. 1, p. 1-14, 2022b.

[101] LI, Q. et al. Efficient room-temperature phosphorescence from nitrogendoped carbon dots in composite matrices. Chemistry of Materials, v. 28, n. 22, 2016.

[102] LI, W. et al. A Universal Strategy for Activating the Multicolor RoomTemperature Afterglow of Carbon Dots in a Boric Acid Matrix. Angewandte Chemie - International Edition, v. 58, n. 22, 2019.

[103] LIM, S. Y.; SHEN, W.; GAO, Z. Carbon quantum dots and their applications. Chemical Society ReviewsRoyal Society of Chemistry, , 7 jan. 2015.

[104] LIN, L. P. et al. Research on the spectral properties of luminescent carbon dots. Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, v. 95, p. 555-561, set. 2012.

[105] LIN, Z. et al. Peroxynitrous-acid-induced chemiluminescence of fluorescent carbon dots for nitrite sensing. Analytical Chemistry, v. 83, n. 21, 2011.

[106] LIU, C. et al. Mechanofluorochromic Carbon Nanodots: Controllable Pressure-Triggered Blue- and Red-Shifted Photoluminescence. Angewandte Chemie International Edition, v. 57, n. 7, 2018.

[107] LIU, H.; YE, T.; MAO, C. Fluorescent carbon nanoparticles derived from candle soot. Angewandte Chemie - International Edition, v. 46, n. 34, 2007. Petição 870250065394, de 29 / 07 / 2025, pág. 31 / 46 29 / 30

[108] LIU, J. et al. Carbon dots in zeolites: A new class of thermally activated delayed fluorescence materials with ultralong lifetimes. Science Advances, v. 3, n. 5, 2017.

[109] LU, S. et al. Near-Infrared Photoluminescent Polymer-Carbon Nanodots with Two-Photon Fluorescence. Advanced Materials, v. 29, n. 15, 18 abr. 2017.

[110] MACKEY, T. K.; LIANG, B. A. The global counterfeit drug trade: Patient safety and public health risks. Journal of Pharmaceutical Sciences, v. 100, n. 11, 2011.

[111] MAYARA, E. et al. Estudo in vitro do potencial citotóxico da Annona muricata L. Journal of Basic and Applied Pharmaceutical Sciences Rev Ciênc Farm Básica Apl, v. 36, n. 2, p. 277-283, 2015.

[112] MEYER, B. N. et al. Brine Shrimp: A Convenient General Bioassay for Active Plant Constituents. [s.l: s.n.].

[113] MILLER, F.; REICHSTEIN, J.; MANDEL, K. Hybrid InorganicOrganic Luminescent Supraparticle Taggants with Switchable Dual-Level ID. Advanced Optical Materials, v. 10, n. 8, 1 abr. 2022.

[114] PARK, M. et al. Controllable Singlet-Triplet Energy Splitting of Graphene Quantum Dots through Oxidation: From Phosphorescence to TADF. Advanced Materials, v. 32, n. 31, 1 ago. 2020.

[115] PAVIA, D. L. et al. Introdução à Espectroscopia. [s.l: s.n.].

[116] SIMÕES, R. et al. Carbon Dots: A Bright Future as Anticounterfeiting Encoding Agents. SmallJohn Wiley and Sons Inc, , 11 jul. 2024.

[117] SUN, Y. et al. The room temperature afterglow mechanism in carbon dots: Current state and further guidance perspective. Carbon, v. 165, 2020.

[118] TAN, J. et al. Large-scale synthesis of N-doped carbon quantum dots and their phosphorescence properties in a polyurethane matrix. Nanoscale, v. 8, n. 8, 2016.

[119] TAO, S. et al. Design of Metal-Free Polymer Carbon Dots: A New Class of Room-Temperature Phosphorescent Materials. Angewandte Chemie - International Edition, v. 57, n. 9, 2018.

[120] TU, D. et al. Boron-Cluster-Enhanced Ultralong Organic Phosphorescence. Angewandte Chemie - International Edition, v. 58, n. 27, 2019a.

[121] TU, D. et al. Boron-Cluster-Enhanced Ultralong Organic Phosphorescence. Angewandte Chemie - International Edition, v. 58, n. 27, 2019b. Petição 870250065394, de 29 / 07 / 2025, pág. 32 / 46 30 / 30

[122] XU, J.; TANABE, S. Persistent luminescence instead of phosphorescence: History, mechanism, and perspective. Journal of Luminescence, v. 205, n. September 2018, p. 581-620, 2019.

[123] XU, S. et al. Excited State Modulation for Organic Afterglow: Materials and Applications. Advanced Materials, v. 28, n. 45, 2016.

[124] XU, X. et al. Electrophoretic analysis and purification of fluorescent single-walled carbon nanotube fragments. Journal of the American Chemical Society, v. 126, n. 40, p. 12736-12737, 2004.

[125] YU, X.; ZHANG, H.; YU, J. Luminescence anti-counterfeiting: From elementary to advanced. Aggregate, v. 2, n. 1, 2021.

[126] ZHAO, J. et al. Triplet photosensitizers: From molecular design to applications. Chemical Society Reviews, v. 42, n. 12, 2013.

[127] ZHAO, W. et al. Rational Molecular Design for Achieving Persistent and Efficient Pure Organic Room-Temperature Phosphorescence. Chem, v. 1, n. 4, 2016.

[128] ZHENG, L. et al. Electrochemiluminescence of water-soluble carbon nanocrystals released electrochemically from graphite. Journal of the American Chemical Society, v. 131, n. 13, 2009.

[129] ZHOU, W. et al. Towards efficient dual-emissive carbon dots through sulfur and nitrogen co-doped. Journal of Materials Chemistry C. Royal Society of Chemistry, , 2017.

[130] ZHU, J. et al. Spectrally Tunable Solid State Fluorescence and RoomTemperature Phosphorescence of Carbon Dots Synthesized via Seeded Growth Method. Advanced Optical Materials, v. 7, n. 9, 2019.

[131] ZHU, S. et al. Highly photoluminescent carbon dots for multicolor patterning, sensors, and bioimaging. Angewandte Chemie - International Edition, v. 52, n. 14, 2013.

[132] ZHU, S. et al. The photoluminescence mechanism in carbon dots (graphene quantum dots, carbon nanodots, and polymer dots): current state and future perspective. Nano Research. Tsinghua University, 1 fev. 2015.

[133] ZHU, S. et al. The photoluminescence mechanism in carbon dots (graphene quantum dots, carbon nanodots, and polymer dots): Current state and future perspective. [s.d.].

[134] ZHUO, S.; SHAO, M.; LEE, S. T. Upconversion and downconversion fluorescent graphene quantum dots: Ultrasonic preparation and photocatalysis. ACS Nano, v. 6, n. 2, 2012. Petição 870250065394, de 29 / 07 / 2025, pág. 33 / 46

Claims

1 / 1 CLAIMS 1. The use of a luminescent material based on Carbon Dots (CDs) with phosphorescence properties at room temperature, prepared by the microwave-assisted method, or any other, characterized by its sensitivity to humidity, for use in inks designed for inkjet printing, intended for information encoding, document authenticity and security applications, where the luminous emission of the material is modulated in response to different levels of ambient humidity.

2. The discovery of a Carbon Dot (CD) composition that exhibits multiple phosphorescence emissions at room temperature, tunable according to the excitation wavelength, characterized by its sensitivity to variations in pH, humidity, and temperature, where the light emission can be modulated in a controlled manner in response to these environmental conditions, being applicable in environmental sensors, monitoring devices, and information encoding technologies.

3. The use of a luminescent material based on Carbon Dots (CDs) with phosphorescence properties at room temperature, prepared by a microwave-assisted method, or any other method, characterized by its sensitivity to humidity, for use in inks designed for inkjet printing, intended for information encoding, document authentication, and security applications, where the luminous emission of the material is modulated in response to different levels of ambient humidity, but not only for inkjet printing, and may also be used in 3D printing using polymeric filament, photopolymerizable resins, or other organic or inorganic matrices. Petition 870250065394, dated 07 / 29 / 2025, pp. 34 / 46

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