Plasmon Resonance Of Nanoparticles Research Articles

High-efficiency green light emission from InGaN/GaN using localized surface plasmon resonance tuned by combination of Ag nanoparticles and dielectric thin film

We achieved significant enhancements in green light emission (550 nm) from InGaN/GaN quantum wells (QWs) by tuning the localized surface plasmon resonance (LSPR) of self-assembled Ag nanoparticles (NPs) through the application of a SiO2 thin film. The LSPR wavelength of Ag NPs was shifted towards shorter wavelengths by 80 nm using a 5 nm SiO2 layer to separate Ag NPs from GaN surface, thereby aligning it effectively with the green region. This strategic placement of Ag NPs and a 5 nm SiO2 film resulted in significant enhancements of photoluminescence (PL) by 15- and 8.8-fold with 5 and 11 nm GaN cap layers, respectively. The LSPR of Ag NPs on a SiO2 thin film facilitated a longer possible distance for the coupling between surface plasmons (SPs) and excitons in a QW. Traditionally, the distance between SPs-generating metal and a QW has been maintained at 10 nm to achieve substantial enhancements. Remarkably, even with a 25 nm cap layer, Ag NPs on a 5 nm SiO2 film boosted PL by 3.1-fold. The enhancements attributable to Ag NPs on SiO2 films were superior, reaching up to 4.8 times greater than those of Ag NPs on GaN surfaces. Additionally, the PL enhancement factors calculated using the finite differential time domain (FDTD) method aligned closely with experimental results.

Photocatalytic H2O2 production and fuel cell performance based on PDI nanobelts enhanced by surface plasmon resonance of gold nanoparticles

The photocatalytic hydrogen peroxide (H2O2) fuel cell represents an innovative self-powered apparatus amalgamating the production and conversion of H2O2 to supply electricity. Using efficient photocatalyst as photoanode to realize two-electron water oxidation to produce H2O2 is considered as a key factor to improve the performance of fuel cell. In this study, perylene imide nanobelts decorated with gold nanoparticles (Au/PDI) were synthesized and subsequently employed as the photoanode to construct a photocatalytic H2O2 fuel cell. This cell can produce H2O2 under irradiation and store it, subsequently utilizing the stored H2O2 to generate electricity in the absence of light. The maximum power density of Au/PDI-based cell could reach 1.07 mW·cm−2 under AM 1.5 G solar light, which has around 1.7 times enhancement compared to PDI-based cell. Meanwhile, a specific capacitance of 5661 mF·cm−2 was obtained after 3 h irradiation. After operating the cell for 12 h, the specific capacitance remained at 50.2 % of its initial value. It is indicated that PDI-based photocatalysts hold considerable promise in water oxidation for H2O2 production. The incorporation of noble nanometals has shown effective enhancement in photocatalytic H2O2 production through the localized surface plasmon resonance (LSPR) effects, thereby enriching the photoanode materials designed for H2O2 fuel cell application.

Utility of Localized Surface Plasmon Resonance of Gold Nanoparticles for Spectrophotometric Determination of Dobutamine in Pharmaceutical Formulations

Utility of Localized Surface Plasmon Resonance of Gold Nanoparticles for Spectrophotometric Determination of Dobutamine in Pharmaceutical Formulations

Doping Engineering To Modulate Surface Plasmon Resonance and Enzyme-like Activities for Enhancing Photoacoustic Imaging-Guided Targeted Cancer Therapy in the Second Near-Infrared Window.

Biological imaging-guided targeted tumor therapy has been a soughtafter goal in the field of cancer diagnosis and treatment. To this end, we proposed a strategy to modulate surface plasmon resonance and endow WO3-x nanoparticles (NPs) with enzyme-like catalytic properties by doping Fe2+ in the structure of the NPs. Doping of the Fe2+ introduced oxygen vacancies into the structure of the NPs, inducing a red shift of the maximum absorption wavelength into the near-infrared II (NIR-II) region and enhancing the photoacoustic (PA) and photothermal properties of the NPs for more effective imaging-guided cancer therapy. Under NIR-II laser irradiation, the Fe-WO3-x NPs produced very strong NIR-II PA and photothermal effects, which significantly enhanced the PA imaging and photothermal treatment effects. On the other hand, Fe2+ in Fe-WO3-x could undergo Fenton reactions with H2O2 in the tumor tissue to generate ·OH for chemodynamic therapy. In addition, Fe-WO3-x can also catalyze the above reactions to produce more reactive oxygen species (ROS) and induce the oxidation of NADH to interfere with intracellular adenosine triphosphate (ATP) synthesis, thereby further improving the efficiency of cancer therapy. Specific imaging of tumor tissue and targeted synergistic therapy was achieved after ligation of a MUC1 aptamer to the surface of the Fe-WO3-x NPs by the complexing of -COOH in MUC1 with tungsten ions on the surface of the NPs. These results demonstrated that Fe-WO3-x NPs could be a promising diagnosis and therapeutic agent for cancer. Such a study opens up new avenues into the rational design of nanodiagnosis and treatment agents for NIR-II PA imaging and cancer therapy.

Miniature computational spectrometer with a plasmonic nanoparticles-in-cavity microfilter array

Optical spectrometers are essential tools for analysing light‒matter interactions, but conventional spectrometers can be complicated and bulky. Recently, efforts have been made to develop miniaturized spectrometers. However, it is challenging to overcome the trade-off between miniaturizing size and retaining performance. Here, we present a complementary metal oxide semiconductor image sensor-based miniature computational spectrometer using a plasmonic nanoparticles-in-cavity microfilter array. Size-controlled silver nanoparticles are directly printed into cavity-length-varying Fabry‒Pérot microcavities, which leverage strong coupling between the localized surface plasmon resonance of the silver nanoparticles and the Fabry‒Pérot microcavity to regulate the transmission spectra and realize large-scale arrayed spectrum-disparate microfilters. Supported by a machine learning-based training process, the miniature computational spectrometer uses artificial intelligence and was demonstrated to measure visible-light spectra at subnanometre resolution. The high scalability of the technological approaches shown here may facilitate the development of high-performance miniature optical spectrometers for extensive applications.

Coupling of Phthalocyanines with Plasmonic Gold Nanoparticles by Click Chemistry for an Enhanced Singlet Oxygen Based Photoelectrochemical Sensing

AbstractCoupling photosensitizers (PSs) with plasmonic nanoparticles increases the photocatalytic activity of PSs as the localized surface plasmon resonance (LSPR) of plasmonic nanoparticles leads to extreme concentration of light in their vicinity known as the near‐field enhancement effect. To realize this in a colloidal phase, efficient conjugation of the PS molecules with the plasmonic nanoparticle surface is critical. In this work, we demonstrate the coupling of phthalocyanine (Pc) molecules with gold nanoparticles (AuNPs) in the colloidal phase via click chemistry. This conjugated Pc‐AuNPs colloidal system is shown to enhance the photocatalytic singlet oxygen (1O2) production over non‐conjugated Pcs and hence improve the photoelectrochemical detection of phenols. The plasmonic enhancement of the 1O2 generation by Pcs was clearly elucidated by complementary experimental and computational classical electromagnetic models. The dependence of plasmonic enhancement on the spectral position of the excitation laser wavelength and the absorbance of the Pc molecules with respect to the wavelength specific near‐field enhancement is clearly demonstrated. A high ∼ 8 times enhancement is obtained with green laser (532 nm) at the LSPR due to the maximum near‐field enhancement at the resonance wavelength.

Photocatalytic performance of Au/Bi4Ti3O12 composite improved by synergistic piezoelectric effect and exciton-plasmon

Bi4Ti3O12 (BiTO) is a typical bismuth-layered Aurivillius ferroelectric material for its potential application in photocatalysis. In this study, Au/BiTO hybrid was fabricated by precipitating Au nanoparticles onto BiTO nanoflake using a sodium citrate reduction route. This integration has led to a remarkable enhancement in the photocatalytic efficiency, which is attributed to the synergistic coupling of piezoelectric effect of BiTO with the localized surface plasmon resonance (LSPR) of Au nanoparticles. The incorporation of Au nanoparticles onto the BiTO matrix has significantly boosted the light absorption and charge carrier separation, thereby augmenting the photocatalytic activity. Notably, Au/BiTO-2 composite exhibits exceptional photocatalytic performance, demonstrating the complete degradation of RhB within 40 min under full-spectrum light irradiation. Moreover, Au/BiTO-2 displays a robust photocatalytic action against other organic pollutants, including methyl orange (MO), ofloxacin (OFLX) and tetracycline hydrochloride (TC). Further enhancement of photocatalytic process is achieved when combing light irradiation with ultrasonic excitation. The ultrasonic waves break the static spontaneous polarization through alternating piezoelectric potential, which accelerates the catalytic reaction. The photocatalytic action rate of Au/BiTO-2 toward RhB reaches a value as high as 0.0984 min−1, which is nearly 2.3 folds increasement compared to that of pristine BiTO. The possible synergistic mechanism caused by piezoelectric effect and exciton-plasmon effect is discussed in detail. The work not only enriches our understanding of the underlying principles but also supply a new strategy to design high-performance catalysts in the field of environmental remediation and energy conversion.

Ultra-Broadband Plasmon Resonance in Gold Nanoparticles Precipitated in ZnO-Al2O3-SiO2 Glass

Optical materials with a tunable localized surface plasmon resonance (LSPR) are of great interest for applications in photonics and optoelectronics. In the present study, we explored the potential of generating an LSPR band with an ultra-broad range of over 1000 nm in gold nanoparticles (NPs), precipitated through a thermal treatment in ZnO-Al2O3-SiO2 glass. Using optical absorption spectroscopy, we demonstrated that the LSPR band’s position and shape can be finely controlled by varying the thermal treatment route. Comprehensive methods including Raman spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy were used to study the glass structure, while computational approaches were used for the theoretical description of the absorption spectra. The obtained results allowed us to suggest a scenario responsible for an abnormal LSPR band broadening that includes a possible interparticle plasmonic coupling effect taking place during the liquid–liquid phase separation of the heat-treated glass. The formation of gold NPs with an ultra-broad LSPR band in glasses holds promise for sensitizing rare earth ion luminescence for new photonics devices.

Fabrication of Nanostructures Consisting of Composite Nanoparticles by Open-Air PLD

We present a two-step physical method for the fabrication of composite nanoparticle-based nanostructures. The proposed method is based on the pulsed laser deposition (PLD) technique performed sequentially in vacuum and in air. As a first step, thin-alloyed films of iron with noble metal were deposited by PLD in vacuum. The films were prepared by ablation of a mosaic target formed by equal iron and gold sectors. As a second step, the as-prepared alloyed films were ablated in air at atmospheric pressure as the laser beam scanned their surface. Two sets of experiments were performed in the second step, namely, by applying nanosecond (ns) and picosecond (ps) laser pulses for ablation. The structure, microstructure, morphology, and optical properties of the samples obtained were studied with respect to the laser ablation regime applied. The implementation of the ablation process in open air resulted in the formation of nanoparticle and/or nanoparticle aggregates in the plasma plume regardless of the ablation regime applied. These nanoparticles and/or nanoaggregates deposited on the substrate formed a complex porous structure. It was found that ablating FeAu films in air by ns pulses resulted in the fabrication of alloyed nanoparticles, while ablation by ps laser pulses results in separation of the metals in the alloy and further oxidation of Fe. In the latter case, the as-deposited structures also contain core–shell type nanoparticles, with the shell consisting of Fe-oxide phase. The obtained structures, regardless of the ablation regime applied, demonstrate a red-shifted plasmon resonance with respect to the plasmon resonance of pure Au nanoparticles.

Complementary absorption effect to improve the optical efficiency of dual-absorption-layered PSCs

By taking advantage of the complementary absorption effect of germanium (Ge) and perovskite, a novel perovskite solar cell (PSC) was proposed by stacking Ge and perovskite thin films to serve as the dual absorption layer. Its absorption spectra and photocurrent were calculated and optimized as a function of the thickness of Ge film by finite element method (FEM). Then, the optical efficiency was further boosted by embedding an array of Ge semi-ellipsoidal nanoparticles within the perovskite film. The predicted maximum photocurrent is revealed to reach 45.72 mA/cm2, which is 2.55 times larger than that of planar referenced PSC. Besides the complementary absorption effect, the localized surface plasmon resonance (LSPR) of Ge nanoparticles and the grating effects of Ge nanoparticle array are revealed to contribute to the obtained Jsc improvement. The present work is insightful for future design and applications of PSCs by introducing Ge thin film and Ge nanoparticles.

Investigation of Melphalan interaction as an alkylating agent with nucleotides by using surface enhanced Raman spectroscopy (SERS)

SERS (Surface Enhanced Raman Spectroscopy) is a new Raman spectroscopy which relies on Surface Plasmon Resonance (SPR) of metal nanoparticles. We have applied colloidal silver and gold nanoparticles as amplifier agents to enhance nucleotide Raman signals. It is observed that without these enhancing agents, it is impossible to investigate nucleotide spectrum due to weak Raman signals. Interaction mechanism of Melphalan, an anticancer drug with four nucleotides (Adenine, Cytosine, Guanine, Thymine) was investigated using SERS to detect and identify changes due to alkylating process in Raman spectra. After incubating Melphalan drug with nucleotides for 24 h at 37 °C, some changes occurred in SERS spectrum and interpretation of SERS spectra revealed the influence of the alkyl substitution on peaks and Raman shifts. After incubation of Melphalan with each nucleotide, intensity of relevant SERS signals assigned to Amid III group of Cytosine and Amid I of Thymine decreased significantly, confirming alkylating taking place. In this study, we also investigated the effect of nanoparticles type on nucleotide spectrum. We could not obtain useful information in the cases of guanine nucleotide. The SERS spectrum of Cytosine as an example of nucleotides in aqueous solution compared to solid state and results demonstrated that in solid state better signals were obtained than in liquid state.

Comparing silver and gold nanoislands’ surface plasmon resonance for bisacodyl and its metabolite quantification in human plasma

Gold and silver nanoparticles have witnessed increased scientific interest due to their colourful colloidal solutions and exceptional applications. Comparing the localized surface plasmon resonance (LSPR) of gold and silver nanoparticles is crucial for understanding and optimizing their optical properties. This comparison informs the design of highly sensitive plasmonic sensors, aids in selecting the most suitable nanoparticles for applications like surface-enhanced infrared spectroscopy (SEIRA) and biomedical imaging, and guides the choice between gold and silver nanoparticles based on their catalytic and photothermal properties. Ultimately, the study of LSPR facilitates the tailored use of these nanoparticles in diverse scientific and technological applications. Two SEIRA methods combined with partial least squares regression (PLSR) chemometric tools were developed. This development is based on the synthesis of homogeneous, high-dense deposited metal nanoparticle islands over the surface of glass substrates to be used as lab-on-chip SEIRA sensors for the determination of bisacodyl (BIS) and its active metabolite in plasma. SEM micrographs revealed the formation of metallic islands of colloidal citrate-capped gold and silver nanoparticles of average sizes of 29.7 and 15 nm, respectively. BIS and its active metabolite were placed on the nanoparticles’ coated substrates to be directly measured, then PLSR chemometric modelling was used for the quantitative determinations. Plasmonic citrate-capped gold nanoparticle substrates showed better performance than those prepared using citrate-capped silver nanoparticles in terms of preparation time, enhancement factor, PLSR model prediction, and quantitative results. This study offers a way to determine BIS and its active metabolite in the concentration range 15–240 ng/mL in human plasma using inexpensive disposable glass-coated substrates that can be prepared in 1 h to get results in seconds with good recovery between 98.77 and 100.64%. The sensors provided fast, simple, selective, molecular-specific and inexpensive procedures to determine molecules in their pure form and biological fluid.

Construction of ternary AuPt/Bi2WO6/ZnIn2S4 heterostructures for photocatalytic degradation of tetrabromobisphenol A

How to fascinate the separation of the photogenerated electrons and holes is very crucial to enhance the photocatalysis of semiconductors. Herein we have prepared AuPt/BWO/ZIS heterostructured photocatalysts by decorating Bi2WO6 (BWO) nanoflakes and AuPt nanoparticles on the surface of ZnIn2S4 (ZIS) hierarchical microspheres. The photocatalysis of the samples was evaluated by degrading tetrabromobisphenol A under simulated-sunlight illumination. It is demonstrated that the ternary AuPt/BWO/ZIS photocatalysts exhibit obviously enhanced photocatalysis in comparison with bare BWO and ZIS as well as the binary BWO/ZIS photocatalysts. The highest photocatalysis is observed for 3%AuPt/40%BWO/ZIS, whose photodegradation performance is improved by 3.9 and 6.2 times over that of single BWO and ZIS, respectively. This phenomenon can be explained due to several reasons: the photocarriers are efficiently separated due to the charge transfer across the BWO/ZIS and AuPt/ZIS interfaces, surface plasmon resonance of AuPt nanoparticles stimulate ZIS to produce additional electron/hole pairs, and the SPR-induced electrons in the AuPt nanoparticles could also take part in the photocatalysis. Additionally, the effect of various factors on the tetrabromobisphenol A degradation was investigated; the degradation pathways of tetrabromobisphenol A and the potential toxicity of the degradation by-products were evaluated.

Development of excitation power-responsive anti-stokes emission wavelength switching and their energy saving induced by localized surface plasmon resonance

We designed an external stimulus-responsive anti-Stokes emission switching using dual-annihilator-based triplet–triplet annihilation upconversion systems. This system, which was constructed by incorporating a palladium porphyrin derivative as a sensitizer and 9,10-diphenylanthracene (DPA) and 9,10-bis(triisopropylsilyl)ethynylanthracene (TIPS) as annihilators into polymer thin films, produced TIPS- and DPA-based anti-Stokes emission under low and high excitation powers, respectively. The mechanism involves the following: under low excitation power, triplet energy transfer from triplet-excited PdOEP to DPA is induced, followed by relay to TIPS. This results in the generation of triplet-excited TIPS, and the subsequent triplet–triplet annihilation between them produces TIPS-based anti-Stokes emission. Conversely, under high excitation power, the high-density triplet-excited DPA, generated through triplet energy transfer from PdOEP, undergoes triplet–triplet annihilation among themselves, resulting in the generation of DPA-based anti-Stokes emission. Additionally, we achieved energy savings by reducing the required excitation power for switching through the utilization of plasmonic metal nanoparticles. The strong local electromagnetic fields associated with the localized surface plasmon resonance of metal nanoparticles enhance the photoexcitation efficiency of PdOEP, subsequently increasing the density of triplet-excited DPA. As a result, anti-Stokes emission switching becomes feasible at lower excitation powers.

Intense charge transfer plasmons in golden nanoparticle dimers connected by conductive molecular linkers.

Golden nanoparticle dimers connected by conjugated molecular linkers 1,2-bis(2-pyridyl)ethylene are produced. The formation of stable dimers with 22nm diameter nanoparticles is confirmed by transmission electron microphotography. The possibility of charge transfer through the linkers between the particles in the dimers is shown by the density functional theory calculations. In addition to localized plasmon resonance of solitary nanoparticles with a wavelength of 530nm, the optical spectra exhibit a new intense absorption peak in the near-infrared range with a wavelength of ∼780nm. The emergent absorption peak is attributed to the charge-transfer plasmon (CTP) mode; the spectra simulated within the CTP developed model agree with the experimental ones. This resonant absorption may be of interest to biomedical applications due to its position in the so-called transmission window of biological tissues. The invitro heating of CTP dimer solution by a laser diode with a wavelength of 792nm proved the efficiency of CTP dimers for achieving a temperature increase of ΔT = 6 °C, which is sufficient for hyperthermia treatment of malignant tumors. This indicates the possibility of using hyperthermia to treat malignant tumors using the material we synthesized.

Localize surface plasmon resonance of gold nanoparticles and their effect on the polyethylene oxide nanocomposite films

Colloidal Gold nanoparticles (AuNPs) with sodium citrate coating were successfully synthesized using a chemical reduction method with an average spherical size of about 20 nm dispersed in the water with high stability. The localized surface plasmon resonance (LSPR) peak was studied by experimental measurement and Mie theory. The absorbance spectrum of AuNPs exhibits a fingerprint peak in the 500–600 nm range, corresponding to the LSPR of AuNPs. Moreover, PEO/AuNPs nanocomposite films with different concentrations of AuNPs were also prepared to evaluate the effect of LSPR of AuNPs on the electrical conductivity and photoconductivity of nanocomposite films. The degree of crystallinity (Xcrys) and melting enthalpy (ΔHm) increase as the AuNPs content in the polymer matrix increases up to 0.5 wt% due to the enhanced nucleation points. The electrical conductivity of pure PEO film is 1.93×10−6 S.cm−1. Increasing the AuNPs concentration to 0.5 wt% in the PEO matrix leads to an increase in the electrical conductivity to 2.28×10−3 S.cm−1 as AuNPs.

Electrical and Optical Switching in Vanadium Dioxide Nanostructures Decorated with Gold Nanoparticles

The electrical parameters of the semiconductor-metal phase transition in vanadium dioxide nanostructures synthesized by chemical vapor deposition on a silicon substrate (100) and decorated with gold nanoparticles with a surface concentration from 3∙109 to 3∙1010 cm–2 are studied. X-ray phase analysis revealed that the synthesized nanostructures of vanadium dioxide contain a monoclinic M1 phase undergoing a phase transition at a temperature of about 68 °C. The morphology of the surface of vanadium dioxide nanostructures coated with gold nanoparticles was studied using a scanning electron microscope and an atomic force microscope. The characteristics of the temperature phase transition of the initial nanostructures and nanostructures decorated with gold nanoparticles are determined. The temperature dependence of the resistance near the phase transition point of the initial nanostructures showed that the resistance jump is about four orders of magnitude, which confirms their high quality. It is shown that an increase in the surface concentration of gold particles to a value of 3∙1010 cm–2 increases the conductivity of vanadium dioxide at room temperature by about two times, and shifts the phase transition temperature by 5 °C: from 68 °C to 63 °C. Optical switching in vanadium dioxide with an array of gold particles with a size of 9 nm is considered by numerical modeling methods. It is established that the response of the electromagnetic wave from the VO2 material during the phase transition is enhanced due to the excitation of localized plasmon resonance in gold nanoparticles and reaches a local maximum in the region of 600 nm. Additionally, this effect is enhanced at angles of incidence near the pseudo-Brewster angle for vanadium dioxide. The considered hybrid VO2–Au nanostructures are promising as basic nanoelements for next-generation computers, as well as for ultrafast and highly sensitive sensors.

Plasmons Enhancing Sub-Bandgap Photoconductivity in TiO2 Nanoparticles Film.

The coupling between sub-bandgap defect states and surface plasmon resonances in Au nanoparticles and its effects on the photoconductivity performance of TiO2 are investigated in both the ultraviolet (UV) and visible spectrum. Incorporating a 2 nm gold nanoparticle layer in the photodetector device architecture creates additional trapping pathways, resulting in a faster current decay under UV illumination and a significant enhancement in the visible photocurrent of TiO2, with an 8-fold enhancement of the defects-related photocurrent. We show that hot electron injection (HEI) and plasmonic resonance energy transfer (PRET) jointly contribute to the observed photoconductivity enhancement. In addition to shedding light on the below-band-edge photoconductivity of TiO2, our work provides insight into new methods to probe and examine the surface defects of metal oxide semiconductors using plasmonic resonances.

Formation of hollow silver nanoparticles under irradiation with ultrashort laser pulses

Abstract We have studied the formation of cavities in spherical silver nanoparticles embedded in silica, irradiated with fs laser pulses that produce an intense electronic excitation. Experimentally determined aspect ratio, i.e. the ratio between the cavity and nanoparticle size, for hollow structures formed under different irradiation conditions shows a very good agreement with values obtained by means of atomistic simulations. According to the predictions of the atomistic model, one can produce at will hollow silver nanoparticles with cavities of tailored dimensions, having an accurate control. Hence, laser irradiation can be used to control and design the optical response by tuning the localized surface plasmon resonances of the hollow nanoparticles.

Watermelon (Citrullus lanatus) Rind Extract-Mediated Synthesis of Manganese (II, III) Oxide Nanoparticles for Potential Theranostic Applications

Plant extracts and microorganisms are widely utilized for the green synthesis of Mn3O4 nanoparticles. In this study, green synthesis of Mn3O4 nanoparticles for theranostic applications was performed using watermelon (Citrullus lanatus) rind extract as a reducing and stabilizing agent. The UV-visible absorption of the nanoparticles at 196 nm is associated with the surface plasmon resonance of Mn3O4 nanoparticles. FT-IR spectra presented the key chemical functional groups associated with the Mn–O vibrations and phytoconstituents of the watermelon rind extract. XRD analysis revealed the single-phase hausmannite crystalline structure of the Mn3O4 nanoparticles with an average crystallite size of 35.2 nm. SEM and TEM images of the synthesized Mn3O4 nanoparticles showed quasi-spherical shapes and a core size of 52.90 ± 8.19 nm and 35.89 ± 0.83 nm, respectively. EDS analysis indicated that the nanoparticles mainly comprised Mn, O, and C. Furthermore, the radical scavenging activity through the DPPH assay showed that the nanoparticles have significant antioxidant therapeutic potential, with an IC50 value of 20.62 ± 0.69 ppm. T1 and T2 relaxivities of Mn3O4 nanoparticles were 5.34 ± 0.11 mM–1s–1 and 63.47 ± 0.60 mM–1s–1, respectively, when measured at a clinically relevant field strength of 1.5 T, confirming their suitability as an MRI contrast agent for diagnostic imaging. These findings imply that the green synthesized Mn3O4 nanoparticles could be used as a theranostic agent for MRI applications.