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Keywords = graphene quantum dots (GQDs)

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17 pages, 7508 KiB  
Article
Supramolecular Graphene Quantum Dots/Porphyrin Complex as Fluorescence Probe for Metal Ion Sensing
by Mariachiara Sarà, Andrea Romeo, Gabriele Lando, Maria Angela Castriciano, Roberto Zagami, Giovanni Neri and Luigi Monsù Scolaro
Int. J. Mol. Sci. 2025, 26(15), 7295; https://doi.org/10.3390/ijms26157295 - 28 Jul 2025
Viewed by 239
Abstract
Graphene quantum dots (GQDs) obtained by microwave-induced pyrolysis of glutamic acid and triethylenetetramine (trien) are fairly stable, emissive, water-soluble, and positively charged nano-systems able to interact with negatively charged meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS4). The stoichiometric control during the preparation affords a [...] Read more.
Graphene quantum dots (GQDs) obtained by microwave-induced pyrolysis of glutamic acid and triethylenetetramine (trien) are fairly stable, emissive, water-soluble, and positively charged nano-systems able to interact with negatively charged meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS4). The stoichiometric control during the preparation affords a supramolecular adduct, GQDs@TPPS4, that exhibits a double fluorescence emission from both the GQDs and the TPPS4 fluorophores. These supramolecular aggregates have an overall negative charge that is responsible for the condensation of cations in the nearby aqueous layer, and a three-fold acceleration of the metalation rates of Cu2+ ions has been observed with respect to the parent porphyrin. Addition of various metal ions leads to some changes in the UV/Vis spectra and has a different impact on the fluorescence emission of GQDs and TPPS4. The quenching efficiency of the TPPS4 emission follows the order Cu2+ > Hg2+ > Cd2+ > Pb2+ ~ Zn2+ ~ Co2+ ~ Ni2+ > Mn2+ ~ Cr3+ >> Mg2+ ~ Ca2+ ~ Ba2+, and it has been related to literature data and to the sitting-atop mechanism that large transition metal ions (e.g., Hg2+ and Cd2+) exhibit in their interaction with the macrocyclic nitrogen atoms of the porphyrin, inducing distortion and accelerating the insertion of smaller metal ions, such as Zn2+. For the most relevant metal ions, emission quenching of the porphyrin evidences a linear behavior in the micromolar range, with the emission of the GQDs being moderately affected through a filter effect. Deliberate pollution of the samples with Zn2+ reveals the ability of the GQDs@TPPS4 adduct to detect sensitively Cu2+, Hg2+, and Cd2+ ions. Full article
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18 pages, 6572 KiB  
Article
Tuning Optical Excitations of Graphene Quantum Dots Through Selective Oxidation: Effect of Epoxy Groups
by Igor V. Ershov, Anatoly A. Lavrentyev, Dmitry L. Romanov and Olga M. Holodova
C 2025, 11(3), 51; https://doi.org/10.3390/c11030051 - 14 Jul 2025
Viewed by 371
Abstract
Graphene quantum dots (GQDs) have strong potential in optoelectronics, particularly in LEDs, photodetectors, solar cells, and nanophotonics. While challenges remain in efficiency and scalability, advances in functionalization and hybrid material integration could soon make them commercially viable for next-generation optoelectronic devices. In this [...] Read more.
Graphene quantum dots (GQDs) have strong potential in optoelectronics, particularly in LEDs, photodetectors, solar cells, and nanophotonics. While challenges remain in efficiency and scalability, advances in functionalization and hybrid material integration could soon make them commercially viable for next-generation optoelectronic devices. In this work, we assess the stability of various epoxy positions and their impact on the electronic and optical properties of GQDs. The oxygen binding energies and the potential barrier heights at different positions of epoxy groups at the edges and in the core of the GQD were estimated. The effect of possible transformations of epoxy groups into other edge configurations on the structural and optical properties of GQDs was evaluated. The results demonstrate that the functionalization of the GQD surface and edges with an epoxy groups at varying binding sites can result in substantial modification of the electronic structure and absorption properties of the GQDs. The prospects of low temperature annealing for controlling optical properties of epoxidized GQDs were discussed. The present computational work offers atomistic insights that can facilitate the rational design of optoelectronic systems based on GQD materials. Full article
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10 pages, 1436 KiB  
Article
Theoretical Investigation of O2 and CO2 Adsorption on Small PdNi Clusters Supported on N-Doped Graphene Quantum Dots
by Brenda García-Hilerio, Lidia Santiago-Silva, Pastor T. Matadamas-Ortiz, Alejandro Gomez-Sanchez, Víctor A. Franco-Luján and Heriberto Cruz-Martínez
C 2025, 11(3), 43; https://doi.org/10.3390/c11030043 - 27 Jun 2025
Viewed by 478
Abstract
A density functional theory (DFT) investigation was conducted to study the O2 and CO2 adsorption on very small Pd3−nNin (n = 0–2) clusters supported on N-doped graphene quantum dots (N-GQDs). The study was carried out in two stages. [...] Read more.
A density functional theory (DFT) investigation was conducted to study the O2 and CO2 adsorption on very small Pd3−nNin (n = 0–2) clusters supported on N-doped graphene quantum dots (N-GQDs). The study was carried out in two stages. First, the interaction between Pd3−nNin (n = 0–2) clusters and N-GQDs was analyzed. Subsequently, the adsorption behavior of O2 and CO2 molecules on the supported clusters was examined. The calculated interaction energies (Eint) of Pd3−nNin (n = 0–2) clusters on N-GQDs were found to be higher than those on pristine graphene, indicating enhanced cluster stability on N-GQDs. Furthermore, the adsorption energies (Eads) of the O2 molecule on the Pd3 and Pd2Ni clusters deposited on N-GQDs were similar. Meanwhile, the PdNi2 cluster deposited on N-GQDs exhibited the highest Eads (−1.740). The Eads of CO2 on Pd3−nNin (n = 0–2) clusters embedded in N-GQDs were observed to be close to or exceed 1 eV. Upon adsorption of O2 and CO2 on the Pd3−nNin (n = 0–2) clusters supported on N-GQDs, an elongation of the O–O and C–O bond lengths was observed, respectively. This structural change may facilitate the dissociation of these molecules on the supported clusters. Full article
(This article belongs to the Section Carbon Materials and Carbon Allotropes)
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12 pages, 958 KiB  
Article
Two-Step Two-Photon Absorption Dynamics in π-π Conjugated Carbazole-Phthalocyanine/Graphene Quantum Dot Hybrids Under Picosecond Pulse Excitation
by Quan Miao, Erping Sun and Yan Xu
Symmetry 2025, 17(6), 949; https://doi.org/10.3390/sym17060949 - 14 Jun 2025
Viewed by 358
Abstract
In carbazole-substituted phthalocyanine complexes 2,3,9,10,16,17,23,24-octakis-(3,6-dibromo-9Hcarbazol) phthalocyaninato zinc(II) (Pc 2) and 2,3,9,10,16,17,23,24-Octakis-(9H-carbazol-9-yl) phthalocyaninato zinc(II) (Pc 4) and their conjugated complexes to graphene quantum dots (GQDs), we studied the nonlinear absorption and propagating of picosecond pulse trains. Each pulse train contains 25 subpulses with width [...] Read more.
In carbazole-substituted phthalocyanine complexes 2,3,9,10,16,17,23,24-octakis-(3,6-dibromo-9Hcarbazol) phthalocyaninato zinc(II) (Pc 2) and 2,3,9,10,16,17,23,24-Octakis-(9H-carbazol-9-yl) phthalocyaninato zinc(II) (Pc 4) and their conjugated complexes to graphene quantum dots (GQDs), we studied the nonlinear absorption and propagating of picosecond pulse trains. Each pulse train contains 25 subpulses with width 100 ps seperated by space 13 ns. During the interaction with pulse trains, the structures of Pcs can be simplified to the five-state energy model. In our calculations, the coupled rate equations and two-dimensional paraxial field were solved using the Crank–Nicholson numerical method. The effects of substituted carbazoles and conjugated GQDs were investigated. Pcs and their conjugated complexes with GQDs exhibit optical limiting (OL) properties, and GQDs could decrease the OL of Pcs. One-photon absorption cross section σS0S1 or σT1T2 is the critical factor to determine the limiting value of energy transmittance in weak- or strong-intensity regions, respectively. The two-step two-photon absorption (TPA) tunnel (S0S1)×(T1T2) is the main absorption mechanism; therefore, the effective population transfer time τST from S0 to T1 is another critical factor that is determined by one-photon absorption cross section σS0S1 and intersystem crossing time τisc. Through further exploration it is found that a high incident intensity will lead to an asymmetric shape of output intensity due to different absorption mechanisms in the front and latter subpulses of the pulse train. Full article
(This article belongs to the Section Engineering and Materials)
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12 pages, 5324 KiB  
Article
One-Step Hydrothermal Synthesis of Multicolour Graphene Quantum Dots and Study of Their Luminescence Mechanism
by Beibei Wang, Ling Sun, Kai Liu, Di Wu, Jinqiu Wang and Fang Geng
Chemistry 2025, 7(3), 94; https://doi.org/10.3390/chemistry7030094 - 6 Jun 2025
Viewed by 549
Abstract
Multicolour graphene quantum dots (GQDs), from blue to orange emitting, were successfully synthesized via a one-step hydrothermal method using potassium hydrogen phthalate and o-phenylenediamine as the raw materials. After purification by silica gel column chromatography, four kinds of GQDs with maximum emission wavelengths [...] Read more.
Multicolour graphene quantum dots (GQDs), from blue to orange emitting, were successfully synthesized via a one-step hydrothermal method using potassium hydrogen phthalate and o-phenylenediamine as the raw materials. After purification by silica gel column chromatography, four kinds of GQDs with maximum emission wavelengths of 420 nm (blue), 500 nm (green), 540 nm (yellow), and 555 nm (orange) were obtained, and all had a high quantum yield (9.7%, 8.8%, 9.3%, and 10.3%, respectively). The structural characterization revealed that the synthesized GQDs had a regular morphology, with a size of 2–3 nm and a thickness of 1–2 nm. The D-band-to-G-band ratio was less than 0.3, indicating that the GQDs had a high degree of graphitization. In addition, the emission peaks of the GQDs were red-shifted as the particle size increased, confirming that their luminescence was dominated by the quantum confinement effect. By analyzing the surface states and the functional groups of the multicolour GQDs, it was found that the GQDs had a similar elemental composition, which further proved that the emission wavelengths did not depend on the surface element composition, but conformed to the luminescence mechanism regulated by the quantum-limited effect. Furthermore, the four types of GQDs exhibited low cytotoxicity and good stability, suggesting their potential applications in biomarkers and for the synchronous detection of a variety of analytes. Full article
(This article belongs to the Section Chemistry at the Nanoscale)
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18 pages, 753 KiB  
Systematic Review
Graphene Quantum Dots for Glioblastoma Treatment and Detection–Systematic Review
by Kacper Kregielewski, Wiktoria Fraczek and Marta Grodzik
Molecules 2025, 30(12), 2483; https://doi.org/10.3390/molecules30122483 - 6 Jun 2025
Viewed by 713
Abstract
Glioblastoma, a highly malignant tumor, has a poor prognosis, necessitating the development of effective therapeutic strategies due to the low success rates of existing treatments. Graphene quantum dots (GQDs) have garnered attention for their unique physicochemical, electronic, and optical properties, along with biocompatibility [...] Read more.
Glioblastoma, a highly malignant tumor, has a poor prognosis, necessitating the development of effective therapeutic strategies due to the low success rates of existing treatments. Graphene quantum dots (GQDs) have garnered attention for their unique physicochemical, electronic, and optical properties, along with biocompatibility and the ability to cross the blood–brain barrier. This systematic review evaluates the current applications of GQDs in glioblastoma management. A search across databases such as PubMed, Science Direct, and Web of Science identified 658 papers, with 10 selected for this review based on the eligibility criteria. Most of the selected studies explored GQDs as pretreatment agents for therapies like chemotherapy and photothermal therapy, alongside their roles in biosensing, bioimaging, and drug delivery. Although research is still limited, this review highlights the significant potential of GQDs as multifunctional platforms in glioblastoma therapy. Further studies are essential to optimize these nanostructures for clinical applications, aiming to improve the precision and effectiveness of treatments while reducing systemic side effects. Full article
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14 pages, 2024 KiB  
Article
A Novel Chiral Molecularly Imprinted Electrochemical Sensor Based on β-CD Functionalized Graphene Quantum Dots for Enantioselective Detection of D-Carnitine
by Feng Yang, Xin Qi, Yan Chen, Kai Tang, Mengyang Fang, Yanwei Song, Jiufen Liu and Lianming Zhang
Foods 2025, 14(9), 1648; https://doi.org/10.3390/foods14091648 - 7 May 2025
Viewed by 618
Abstract
In this study, β-cyclodextrin (β-CD) functionalized graphene quantum dots (GQDs) was employed to augment the array of chiral recognition sites, thereby enhancing the affinity of GQDs/β-CD composite for imprinting molecules and realizing heightened chiral selectivity. The incorporation of GQDs/β-CD into the synthesis of [...] Read more.
In this study, β-cyclodextrin (β-CD) functionalized graphene quantum dots (GQDs) was employed to augment the array of chiral recognition sites, thereby enhancing the affinity of GQDs/β-CD composite for imprinting molecules and realizing heightened chiral selectivity. The incorporation of GQDs/β-CD into the synthesis of molecularly imprinted polymers (MIPs), synergizing with the host-guest inclusion properties of β-CD and the abundant carboxyl groups of GQDs, enhanced the chiral recognition capacity of MIPs materials. Consequently, a novel MIPs/(GQDs/β-CD) sensor with chiral recognition capabilities tailored for D-carnitine was successfully fabricated. The binding mechanism between GQDs/β-CD and D-carnitine was elucidated via Ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy. The variation in the response signal (ΔI) of the probe molecule exhibited a linear correlation with the logarithm of D-carnitine concentration (lgC) in the range of 1.0 × 10−12 mol/L to 1.0 × 10−9 mol/L, and the detection limit (3δ/S) was calculated as 2.35 × 10−13 mol/L. These results underscore a 7.15-fold enhancement in the selectivity of MIPs/(GQDs/β-CD) sensor for D-carnitine recognition. Moreover, the sensor presented commendable efficacy in real-world scenarios, yielding recovery rates ranging from 98.5% to 103.0% during the determination of D-carnitine content in real samples. Full article
(This article belongs to the Special Issue Development and Application of Biosensors in the Food Field)
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23 pages, 5249 KiB  
Review
Carbon Nanotube-Based Field-Effect Transistor Biosensors for Biomedical Applications: Decadal Developments and Advancements (2016–2025)
by Joydip Sengupta and Chaudhery Mustansar Hussain
Biosensors 2025, 15(5), 296; https://doi.org/10.3390/bios15050296 - 7 May 2025
Cited by 2 | Viewed by 1413
Abstract
Advancements in carbon nanotube-based FET (CNT-FET) biosensors from 2016 to 2025 have boosted their sensitivity, specificity, and rapid detection performance for biomedical purposes. This review highlights key innovations in transducer materials, functionalization strategies, and device architectures, including floating-gate CNT-FETs for detecting cancer biomarkers, [...] Read more.
Advancements in carbon nanotube-based FET (CNT-FET) biosensors from 2016 to 2025 have boosted their sensitivity, specificity, and rapid detection performance for biomedical purposes. This review highlights key innovations in transducer materials, functionalization strategies, and device architectures, including floating-gate CNT-FETs for detecting cancer biomarkers, infectious disease antigens, and neurodegenerative disease markers. Novel approaches, such as dual-microfluidic field-effect biosensor (dual-MFB) structures and carboxylated graphene quantum dot (cGQD) coupling, have further expanded their diagnostic potential. Despite significant progress, challenges in scalability, reproducibility, and long-term stability remain. Overall, this work highlights the transformative potential of CNT-FET biosensors while outlining a roadmap for translating laboratory innovations into practical, high-impact biomedical applications. Full article
(This article belongs to the Special Issue Biosensors Based on Transistors)
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12 pages, 3111 KiB  
Article
Effect of Annealing Temperature on the Photoluminescence Blue Shift of Nitrogen-Doped Graphene Quantum Dots
by Xiaofen Xu, Jun Guo, Lu Han, Huimin Fan and Fei Tong
Materials 2025, 18(9), 2094; https://doi.org/10.3390/ma18092094 - 2 May 2025
Viewed by 507
Abstract
Nitrogen-doped graphene quantum dots (NGQDs) are made by heating a mixture of GQDs and ammonia using a thermochemical method. The optical properties of the samples were studied. Here, the role of the temperature used in the annealing process is investigated. It is found [...] Read more.
Nitrogen-doped graphene quantum dots (NGQDs) are made by heating a mixture of GQDs and ammonia using a thermochemical method. The optical properties of the samples were studied. Here, the role of the temperature used in the annealing process is investigated. It is found that with the increase in heating temperature, the sp2 fraction content continuously increases, and the photoluminescence (PL) blue shift continuously increases. The 550 nm peak of GQDs shifts from 550 nm to 513 nm NGQDs synthesized at 300 °C. The normalized PL intensity shows a significant blue shift in the emission peak of the NGQD samples compared to the GQDs. The peak position of the GQDs is 555 nm, while the peak positions of the NGQDs are 511 nm for NGQDs-250, 488 nm for NGQDs-300, and 480 nm for NGQDs-350. Using a simple thermochemical method, we can effectively dope N into GQDs, and it is evident from the electron energy loss spectra that N doping induces the emergence of a new energy level in the electronic structure, which alters the optical properties of NGQDs. Full article
(This article belongs to the Section Carbon Materials)
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22 pages, 5142 KiB  
Article
ZnFe2O4/GQDs Nanoparticles as Peroxidase Mimics for Sensitive and Selective Colorimetric Detection of Glucose in Real Samples
by Claudia Cirillo, Mariagrazia Iuliano and Maria Sarno
Micromachines 2025, 16(5), 520; https://doi.org/10.3390/mi16050520 - 28 Apr 2025
Viewed by 542
Abstract
Glucose detection is critical in addressing health and medical issues related to irregular blood levels. Colorimetry, a simple, cost-effective, and visually straightforward method, is often employed. Traditional enzymatic detection methods face drawbacks such as high costs, limited stability, and operational challenges. To overcome [...] Read more.
Glucose detection is critical in addressing health and medical issues related to irregular blood levels. Colorimetry, a simple, cost-effective, and visually straightforward method, is often employed. Traditional enzymatic detection methods face drawbacks such as high costs, limited stability, and operational challenges. To overcome these, enzyme mimics or artificial nano-enzymes based on inorganic nanomaterials have garnered attention, but their cost and susceptibility to inactivation limit applications. This study presents a ZnFe2O4/GQDs nanocomposite as an innovative enzyme mimic, addressing key requirements like low cost, high stability, biocompatibility, and wide operational range. Synthesized using a simple and inexpensive method, the composite benefits from the synergistic interaction between ZnFe2O4 nanoparticles and graphene quantum dots (GQDs), resulting in excellent magnetic properties, high surface area, and functional versatility. The material demonstrated remarkable sensitivity with a detection limit of 7.0 μM across a range of 5–500 μM and achieved efficient peroxidase-like activity with Km values of 0.072 and 0.068 mM and Vmax of 4.58 × 10⁻8 and 8.29 × 10⁻8 M/s for TMB and H2O2, respectively. The nanocomposite also exhibited robust recyclability, retaining performance over six reuse cycles. Full article
(This article belongs to the Section C:Chemistry)
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15 pages, 3307 KiB  
Article
Enhanced Antibacterial Activity of Sodium Titanate/Graphene Quantum Dot Self-Supporting Membranes via Synergistic Photocatalysis and Physical Cutting
by Shuling Shen, Ji Wang, Yaru Li, Xinjuan Liu, Zhihong Tang, Huixin Xiu, Jing Li and Guanglei Zhou
Materials 2025, 18(8), 1844; https://doi.org/10.3390/ma18081844 - 17 Apr 2025
Viewed by 432
Abstract
Graphene quantum dots (GQDs) show significant promise as antibacterial agents, but their application is hindered by several limitations, including potential cytotoxicity at high concentrations, as well as concerns regarding aggregation and reusability. In this study, sodium titanate (NTO) ultralong nanotubes were utilized as [...] Read more.
Graphene quantum dots (GQDs) show significant promise as antibacterial agents, but their application is hindered by several limitations, including potential cytotoxicity at high concentrations, as well as concerns regarding aggregation and reusability. In this study, sodium titanate (NTO) ultralong nanotubes were utilized as both a photocatalyst and support for GQDs. The NTO/GQDs heterojunction was formed by embedding GQDs nanoplates onto the walls of NTO nanotubes. This integration significantly improved the visible light absorption and enhanced the separation and transfer of electron–hole pairs, leading to an efficient photocatalytic antibacterial process. The NTO/GQD-8 self-supporting membrane composed of these ultralong nanotubes demonstrated outstanding antibacterial efficiency (99.99%) against E. coli and exhibited remarkable cycling stability. Radical scavenging experiments revealed that ∙OH and e were the primary reactive species driving the photocatalytic antibacterial process. Notably, NTO and NTO/GQDs-8 exhibited distinct antibacterial outcomes. After photocatalytic treatment with NTO/GQDs-8, E. coli cells were completely fragmented, with no intact cell structures remaining due to the synergy effect of GQDs’ physical cutting during photocatalytic treatment. Full article
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18 pages, 4954 KiB  
Article
In Situ Growth of Au NPs on Nitrogen-Doped Graphene Quantum Dots Decorated Graphene Composites for the Construction of an Electrochemical Immunosensor and Its Application in CEA Detection
by Zhengzheng Yan, Lujie Wang and Fei Yan
Molecules 2025, 30(6), 1347; https://doi.org/10.3390/molecules30061347 - 17 Mar 2025
Cited by 2 | Viewed by 1063
Abstract
Carcinoembryonic antigen (CEA) is an important tumor biomarker for the early clinical diagnosis of various cancers, and, therefore, the accurate and sensitive quantitative determination of CEA is of vital significance. In this study, we demonstrated the in situ growth of Au nanoparticles (AuNPs) [...] Read more.
Carcinoembryonic antigen (CEA) is an important tumor biomarker for the early clinical diagnosis of various cancers, and, therefore, the accurate and sensitive quantitative determination of CEA is of vital significance. In this study, we demonstrated the in situ growth of Au nanoparticles (AuNPs) on nitrogen-doped graphene quantum dots (N-GQDs) decorated reduced graphene oxide (rGO) nanocomposites by using simple drop-coating and electrochemical deposition methods. N-GQDs@rGO can be formed through the π–π stacking interaction and possesses a high specific surface area and many functional groups, providing lots of anchor sites (amino moieties in NGQDs) for the in situ electrochemical growth of AuNPs without the addition of reductants and protective agents. Such AuNPs/N-GQDs@rGO ternary nanocomposites combine the characteristics of three nanomaterials, showing a large surface area, excellent solubility, good conductivity, catalytic activity, a simple fabrication process, and notable stability, which are further used to construct a label-free electrochemical immunosensor for the determination of CEA. Under the optimized experimental conditions, the AuNPs/N-GQDs@rGO-based electrochemical immunosensor achieves a broad linear response, ranging from 1 pg/mL to 0.5 μg/mL and a low detection limit of 0.13 pg/mL. Moreover, the AuNPs/N-GQDs@rGO-based electrochemical immunosensor shows exceptional selectivity, anti-interference, and anti-fouling capabilities for the direct analysis of CEA amounts in fetal bovine serum samples, showing vast potential in the clinical screening of cancer. Full article
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13 pages, 3972 KiB  
Article
Optimized Sensitivity in Copper(II) Ion Detection: Sustainable Fabrication of Fluorescence Red-Shifted Graphene Quantum Dots via Electron-Withdrawing Modulation
by Weitao Li, Qian Niu, Xinglong Pang, Shang Li, Yang Liu, Boyu Li, Shuangyan Li, Lei Wang, Huazhang Guo and Liang Wang
Molecules 2025, 30(6), 1244; https://doi.org/10.3390/molecules30061244 - 10 Mar 2025
Cited by 3 | Viewed by 838
Abstract
Graphene quantum dots (GQDs) represent a class of promising nanomaterials characterized by adjustable optical properties, making them well suited for applications in biosensing and chemical detection. However, challenges persist in achieving scalable, cost-effective synthesis and enhancing detection sensitivity. In this study, we have [...] Read more.
Graphene quantum dots (GQDs) represent a class of promising nanomaterials characterized by adjustable optical properties, making them well suited for applications in biosensing and chemical detection. However, challenges persist in achieving scalable, cost-effective synthesis and enhancing detection sensitivity. In this study, we have developed a simple and environmentally friendly method to prepare blue graphene quantum dots, c-GQDs, using nitronaphthalene as a precursor, and yellow graphene quantum dots, y-GQDs, using nitronaphthalene doped acid. The quantum yield is 29.75%, and the average thickness is 2.08 nm and 3.95 nm, respectively. The synthesized c-GQDs exhibit a prominent cyan fluorescence at a wavelength of 490 nm under excitation at 380 nm, while the y-GQDs show a distinct yellow fluorescence at a wavelength of 540 nm under excitation at 494 nm. The introduction of p-aminobenzoic acid (PABA) introduced a marked red shift in fluorescence, attributed to the electron-withdrawing effect of the carboxyl groups on PABA. This key finding significantly enhanced the sensitivity of GQDs for detecting trace copper(II) ions (Cu2+), a heavy metal contaminant posing serious environmental risks. The fluorescence of the GQDs was selectively quenched in the presence of Cu2+, facilitating accurate and sensitive detection even in complex ion matrices. Mechanistic studies revealed that the quenching effect is driven by strong static quenching interactions, which inhibit non-radiative transitions. This work not only introduces a scalable method for producing high-performance GQDs but also highlights their potential as effective fluorescent probes for environmental monitoring and heavy metal ion detection. Full article
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13 pages, 3194 KiB  
Article
Fluorescence Quenching of Graphene Quantum Dots from Orange Peel for Methyl Orange Detection
by Weitao Li, Yang Liu, Xinglong Pang, Yuanhao Huang, Zeyun Dong, Qian Niu, Yuping Xiong, Shang Li, Shuai Li, Lei Wang, Huazhang Guo, Saisai Cui, Shenpeng Hu, Yuenan Li, Tiantian Cha and Liang Wang
Nanomaterials 2025, 15(5), 376; https://doi.org/10.3390/nano15050376 - 28 Feb 2025
Cited by 5 | Viewed by 1347
Abstract
Methyl orange (MO) is an organic synthetic dye widely used in laboratory and industrial applications. In laboratory settings, it serves as an acid–base indicator due to its distinct color change in both acidic and alkaline environments. Industrially, it is primarily utilized in the [...] Read more.
Methyl orange (MO) is an organic synthetic dye widely used in laboratory and industrial applications. In laboratory settings, it serves as an acid–base indicator due to its distinct color change in both acidic and alkaline environments. Industrially, it is primarily utilized in the textile industry for its ultraviolet (UV) absorption properties. However, the discharge and leakage of methyl orange into the environment can cause severe ecological damage and pose potential carcinogenic and teratogenic risks to human health. Therefore, detecting and quantifying the concentration of methyl orange in various matrices is crucial. This study reports the synthesis of graphene quantum dots (GQDs) from orange peel as a precursor, using ethanol and dimethylformamide (DMF) as solvents. Cyan (c-GQDs) and yellow (y-GQDs) graphene quantum dots were synthesized through a bottom-up hydrothermal method. The difference in color is attributed to the redshift caused by the varying ratio of pyridine nitrogen to pyrrole nitrogen. These GQDs exhibited notable optical properties, with c-GQDs emitting cyan fluorescence and y-GQDs emitting yellow fluorescence under UV light. To investigate fluorescence quenching effects, nine commonly used dyes were tested, and all were found to quench the fluorescence of y-GQDs, with methyl orange having the most significant effect. The fluorescence quenching of orange peel-derived GQDs in the presence of methyl orange is attributed to poor dispersion in DMF solution. Additionally, the GQDs possess high specific surface area, abundant surface functional groups, and excellent electronic conductivity, which contribute to their effective fluorescence quenching performance. The average thickness of y-GQDs (the vertical dimension from the substrate upwards) was 3.51 nm, confirming their graphene-like structure. They emitted yellow fluorescence within the wavelength range of 450–530 nm. Notably, a significant linear correlation was found between the concentration of methyl orange and the fluorescence intensity of y-GQDs (regression coefficient = 0.9954), indicating the potential of GQDs as effective sensing materials for organic pollutant detection. Full article
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17 pages, 4536 KiB  
Article
Graphene Quantum Dots in Bacterial Cellulose Hydrogels for Visible Light-Activated Antibiofilm and Angiogenesis in Infection Management
by Danica Z. Zmejkoski, Nemanja M. Zdravković, Dijana D. Mitić, Zoran M. Marković, Milica D. Budimir Filimonović, Dušan D. Milivojević and Biljana M. Todorović Marković
Int. J. Mol. Sci. 2025, 26(3), 1053; https://doi.org/10.3390/ijms26031053 - 26 Jan 2025
Cited by 1 | Viewed by 1164
Abstract
A novel bacterial cellulose (BC)-based composite hydrogel with graphene quantum dots (BC-GQDs) was developed for photodynamic therapy using blue and green light (BC-GQD_blue and BC-GQD_green) to target pathogenic bacterial biofilms. This approach aims to address complications in treating nosocomial infections and combating multi-drug-resistant [...] Read more.
A novel bacterial cellulose (BC)-based composite hydrogel with graphene quantum dots (BC-GQDs) was developed for photodynamic therapy using blue and green light (BC-GQD_blue and BC-GQD_green) to target pathogenic bacterial biofilms. This approach aims to address complications in treating nosocomial infections and combating multi-drug-resistant organisms. Short-term illumination (30 min) of both BC-GQD samples led to singlet oxygen production and a reduction in pathogenic biofilms. Significant antibiofilm activity (>50% reduction) was achieved against Staphylococcus aureus and Escherichia coli with BC-GQD_green, and against Pseudomonas aeruginosa with BC-GQD_blue. Atomic force microscopy images revealed a substantial decrease in biofilm mass, accompanied by changes in surface roughness and area, further confirming the antibiofilm efficacy of BC-GQDs under blue and green light, without any observed chemical alterations. Additionally, the biocompatibility of BC-GQDs was demonstrated with human gingival fibroblasts (HGFs). For the first time, in vitro studies explored the visible light-induced potential of BC-GQD composites to promote wound healing processes, showing increased migratory potential and the upregulation of eNOS and MMP9 gene expressions in HGFs. Chemical characterization revealed a 70 nm upshift in the photoluminescence emission spectra compared to the excitation wavelength. These novel photoactive BC-GQD hydrogel composites show great promise as effective agents for wound healing regeneration and infection management. Full article
(This article belongs to the Section Materials Science)
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