Gold Shell Research Articles

Plasmonic Hinge Modes in Metal-Coated Nanolasers.

Plasmonic lasers have traditionally been built on flat metal substrates. Here, we introduce substrate-free plasmonic lasers created by coating semiconductor particles with an optically thin layer of noble metal. This architecture supports plasmonic "hinge" modes highly localized along the particle's edges and corners, exhibiting Purcell factors exceeding 100 and Q-factors of 15-20 near the plasmon resonance frequency. We demonstrate hinge-mode lasing in submicron CsPbBr3 perovskite cubes encapsulated with conformal 15-nm-thick gold shells. The lasing is achieved with 480-nm nanosecond pumping at 10 pJ/μm2 through the translucent gold layer, producing a line width of 0.6 at 538 nm. Their rapidly decaying evanescent fields outside the gold coating show distinct sensitivities to long- and short-range external perturbations. Our results suggest the potential of these novel laser modes for sensing and imaging applications.

Change of composition and surface plasmon resonance of Pd/Au core/shell nanoparticles triggered by CO adsorption.

Controlling composition and plasmonic response of bimetallic nanoparticles (NPs) is of great relevance to tune their catalytic activity. Herein, we demonstrate reversible composition and plasmonic response transitions from a core/shell to a bimetallic alloyed palladium/gold NP triggered by CO adsorption and sample temperature. The use of self-organized growth on alumina template film allows scrutinizing the impact of core size and shell thickness onto NP geometry and plasmonic response. Topography, molecular adsorption, and plasmonic response are addressed by scanning tunneling microscopy, vibrational sum frequency generation (SFG) spectroscopy, and surface differential reflectance spectroscopy, respectively. Modeling CO dipolar interaction and optical reflectivity corroborate the experimental findings. We demonstrate that probing CO adsorption sites by SFG is a remarkably sensitive and relevant method to investigate shell composition and follow in real-time Pd atom migration between the core and the shell. Pd-Au alloying is limited to the first two monolayers of the shell and no plasmonic response is found, while for a thicker shell, a plasmonic response is observed, concomitant with a lower Pd concentration in the shell. Above 10-4mbar, at room temperature, CO adsorption triggers the shell restructuration, forming a Pd-Au alloy that weakens the plasmonic response via Pd migration from the core to the shell. NP annealing at 550K, after pumping CO, leads to the desorption of remaining CO and gives enough mobility for Pd to migrate back inside the core and recover a pure gold shell with its original plasmonic response. This work demonstrates that surface stoichiometry and plasmonic response can be tuned by using CO adsorption and NP annealing.

Nanoscale dosimetry for a radioisotope-labeled metal nanoparticle using MCNP6.2 and Geant4.

Metal nanoparticles (MNPs) labeled with radioisotopes (RIs) are utilized as radio-enhancers due to their ability to amplify the radiation dose in their immediate vicinity. A thorough understanding of nanoscale dosimetry around MNPs enables their effective application in radiotherapy. However, nanoscale dosimetry around MNPs still requires further investigation. This study aims to provide insight into the radio-enhancement effects of MNPs by elucidating nanoscale dosimetry surrounding MNPs labeled with Auger-emitting RIs. We particularly focus on distinguishing the respective dose contributions of photons and electrons emitted by Auger-emitting RIs in the context of dose enhancement. A 50nm diameter NP of silver (Ag) core and gold (Au) shell (Ag@Au NP) was assumed to emit mono-energetic electrons and photons (3, 5, 10, 20, and 30keV), or the energy spectrum corresponding to one of three Auger-emitting RIs (103Pd, 125I, and 131Cs) from the Ag core. Nanoscale radial dose distributions around a single radioactive Ag@Au NP were evaluated in spherical shells of water. Monte Carlo simulations were conducted using single-event and track structure transport methods implemented in MCNP6.2 and Geant4-DNA-Au physics, respectively. To evaluate the extent of radio-enhancement by the Ag@Au NP, two scenarios were considered: Ag@Au NPs (Au shell included) and Ag@water NPs (Au shell replaced by water). The radial doses of 10, 20, and 30keV electrons estimated by both codes were comparable. However, the radial doses of 3 and 5keV electrons by MCNP6.2 were much larger near the NP surface than those by Geant4. There was a dose enhancement of a few % to tens % by the Au shell in the region of the NP surface to 10µm, depending on the electron energy. The radial doses of photons with the Au shell were higher up to their secondary electron ranges than those without the Au shell. The maximum dose enhancement factor of photons occurred at 20keV and was 63.4 by MCNP6.2 and 50.5 by Geant4. The overall radial doses of electrons were 1-2 orders of magnitude larger than those of photons. As a result, in cases of RIs emitting both electrons and photons, the radial doses up to electron ranges were dominantly governed by electrons. The dose enhancement estimated by both codes for the RIs ranged from a few % except in the immediate vicinity of the NP surface. Given the dominant contribution of electrons to radial doses of MNP labeled with Auger-emitting RIs, physical dose enhancement expected by interactions with photons was hindered. Since there are no available RIs emitting exclusively photons, achieving enhanced physical doses within a cell through a combination of MNPs and RIs appears currently unattainable. The radial doses of photons near the NP surface exhibited considerable discrepancies between the codes, primarily attributed to low-energy electrons. The difference may arise from higher cross-sections of Au inelastic scattering in Geant4-DNA-Au compared to MCNP6.2.

Lateral Flow Assay Biotesting by Utilizing Plasmonic Nanoparticles Made of Inexpensive Metals─Replacing Colloidal Gold.

Nanoparticles (NPs) can be conjugated with diverse biomolecules and employed in biosensing to detect target analytes in biological samples. This proven concept was primarily used during the COVID-19 pandemic with gold-NP-based lateral flow assays (LFAs). Considering the gold price and its worldwide depletion, here we show that novel plasmonic NPs based on inexpensive metals, titanium nitride (TiN) and copper covered with a gold shell (Cu@Au), perform comparable to or even better than gold nanoparticles. After conjugation, these novel nanoparticles provided high figures of merit for LFA testing, such as high signals and specificity and robust naked-eye signal recognition. Since the main cost of Au NPs in commercial testing kits is the colloidal synthesis, our development with the Cu@Au and the laser-ablation-fabricated TiN NPs is exciting, offering potentially inexpensive plasmonic nanomaterials for various bioapplications. Moreover, our machine learning study showed that biodetection with TiN is more accurate than that with Au.

Hydrogels of Alginate Derivative‐Encased Nanodots Featuring Carbon‐Coated Manganese Ferrite Cores with Gold Shells to Offer Antiangiogenesis with Multimodal Imaging‐Based Theranostics

AbstractThe investigation seeks to develop gold‐shelled carbon‐coated manganese ferrite nanodots enclosed within oxidized alginate polymeric hydrogels (MNF@C‐Au@OSA) to improve encapsulation efficiency, biocompatibility, and multimodal imaging capabilities. These engineered particles, MNF@C‐Au@OSA, are crafted through a hydrothermal synthesis, succeeded by the application of gold nanoparticle shelling and subsequent encapsulation within hydrogels derived from synthesized alginate derivatives, enhancing their overall appeal. Diverse characterization methodologies are employed in order to validate the multiple steps of the synthesis process. The resulting engineered nanoparticles exhibit dual‐mode (T1 and T2) magnetic resonance imaging (MRI) contrast capabilities and compatibility with computed tomography (CT) and fluorescence‐based imaging. To illustrate minimal toxicity, A375 cell lines are utilized for in vitro testing, whereas zebrafish embryos are employed for in vivo assessments. A Chorioallantoic Membrane Model (CAM) is used to establish the antiangiogenic characteristics of MNF@C‐Au@OSA, which is confirmed by histopathological observations. Taking these studies together, one can conclude that the engineered MNF@C‐Au@OSA possesses multimodal imaging capabilities and has demonstrated antiangiogenic properties, thereby establishing them as potential theranostic agents.

Dual-Modal Colorimetric and Surface-Enhanced Raman Scattering (SERS)-Based Lateral Flow Immunoassay for Ultrasensitive Detection of SARS-CoV-2 Using a Plasmonic Gold Nanocrown.

The 2019 coronavirus disease (COVID-19) outbreak created an unprecedented need for rapid, sensitive, and cost-effective point-of-care diagnostic tests to prevent and mitigate the spread of the SARS-CoV-2 virus. Herein, we demonstrated an advanced lateral flow immunoassay (LFIA) platform with dual-functional [colorimetric and surface-enhanced Raman scattering (SERS)] detection of the spike 1 (S1) protein of SARS-CoV-2. The nanosensor was integrated with a specially designed core-gap-shell morphology consisting of a gold shell decorated with external nanospheres, a structure referred to as gold nanocrown (GNC), labeled with a Raman reporter molecule 1,3,3,1',3',3'-hexamethyl-2,2'-indotricarbocyanine iodide (HITC) to produce a strong colorimetric signal as well as an enhanced SERS signal. Among the different plasmonics-active GNC nanostructures, the GNC-2 morphology, which has a shell decorated with an optimum number and size of nanospheres, produces an intense dark-blue colorimetric signal and ultrahigh SERS signal. The limit of detection (LOD) of the S1 protein via colorimetric detection LFIA was determined to be 91.24 pg/mL. On the other hand, the LOD for the SERS LFIA method was more than three orders of magnitude lower at 57.21 fg/mL. Furthermore, we analyzed the performance of the GNC-2 nanosensor for directly analyzing the S1 protein spiked in saliva samples without any sample pretreatment and achieving the LOD as low as 39.65 fg/mL using SERS-based plasmonics-enhanced LFIA, indicating ultrahigh detection sensitivity. Overall, our GNC nanosensor showed excellent sensitivity, reproducibility, and rapid detection of the SARS-CoV-2 S1 protein, demonstrating excellent potential as a promising point-of-care platform for the early detection of respiratory virus infections.

Study of the photothermal response of a multilayer structure doped with VO2@Au nanoshells

In this paper, we demonstrate a theoretical study of a multiphysics problem to solve for the photothermal response of a one-dimensional multilayer structure containing a layer doped with VO2@Au nanoshells. The VO2@Au nanoshell consists of a gold (Au) shell and a core of the phase change material vanadium dioxide (VO2) where the VO2 core transitions from a semiconductor state to a conductor state at the critical temperature of 68 °C. This behaviour results in thermal induced optical tunability through this reversible phase change of the VO2, due to the temperature dependent optical and thermal properties. The presence of the VO2 core, functioning as an ultra-fast and reversible optical phase-change material, leads to the emergence of photothermal induced bistability. The layer doped with the VO2@Au nanoshell is approximated as an effective medium using the Maxwell-Garnett Theory to enable an analytical solution. In this study, the optical response of the multilayer structure is obtained using the Transfer Matrix Method, while the thermal response for both stationary and transient states is solved using the Green’s Function Method and Kirchhoff’s Transformation. These equations are interconnected through the heat source term in the heat diffusion equations, representing the local heat generation induced by the continuous-wave laser applied to the structure. Our findings indicate that at the wavelengths of 658 nm and 747 nm, there are two distinct photothermal responses arising from the phase change of the VO2 core. At these wavelengths, the absorption of light increases and decreases, respectively, because of the VO2 phase change. This analytical method not only offers a thorough exploration of the fundamentals of induced photothermal responses in multilayer structures but also holds considerable potential for various applications, including solar cells, photothermal therapy, and nanothermal sensors.

Synthesis, Characterization and Biosafety Evaluation of Hollow Gold Nanospheres.

In order to assess the biosafety of HAuNS using zebrafish models and the cancer cell lines HepG2, HEK293, and A549, this study prepared HAuNS in a variety of sizes and alterations. By oxidizing cobalt nanoparticles encased in gold shells, HAuNS were created. In the meantime, PEG- and PEI-coated HAuNS were created. The diameters of the HAuNS that were produced were 30~40 nm, 50~60 nm, and 70~80 nm. MTT assay was used to assess the toxicity of HAuNS on HepG2, HEK293, and A549 cells. For the investigation of their toxicities, HAuNS (50~60 nm) of various concentrations were incubated with zebrafish embryos. Then, cell death was determined using acridine orange staining. In a cell line model, it was demonstrated that purified HAuNS exhibit lower toxicity than unpurified HAuNS. Meanwhile, it was discovered that surface-modified HAuNS was less hazardous than unmodified HAuNS. Unpurified HAuNS (50.60 nm) exposure to embryos caused deformity and increased mortality. Moreover, embryos exposed to HAuNS displayed an increase in cell death, showing that HAuNS can put zebrafish under physiological stress. The possible toxicity of HAuNS is now more understood thanks to this investigation. The details could improve our comprehension of the nanotoxicity of medication delivery systems. Comparing HAuNS (50~60 nm) to the other two particle sizes, its toxicity was quite low. Compared to unpurified HAuNS, purified HAuNS displayed less toxicity. Comparing PEI-HAuNS and HAuNS to PEG-HAuNS, cytotoxicity was found to be lower. Our data support the use of pure HAuNS, HAuNS-PEG, and HAuNS (50~60 nm) as possible photothermal conductors when seen as a whole.

A nanogap-enhanced SERS nanotag-based lateral flow assay for ultrasensitive and simultaneous monitoring of SARS-CoV-2 S and NP antigens.

A lateral flow assay (LFA) strip based on dual 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB)-encoded satellite Fe3O4@Au (Mag@Au) SERS tags with nanogap is reported for ultrasensitive and simultaneous diagnosis of two SARS-CoV-2 functional proteins. Composed of Fe3O4 core, satellite gold shell with nanogaps, and double-layer DTNB, the Mag@Au nanoparticles with an average size of 238nm were designed as multifunctional tags to efficiently enrich the target SARS-CoV-2 protein from complex samples, significantly enhancing theSERS signal of the LFA strip and provide quantitative SERS detection of analyte on test lines. The developed dual DTNB-encoded satellite Mag@Au-based LFA allowed simultaneous quantification of spike (S) protein and nucleocapsid (NP) protein with detection limits of 23pgmL-1 and 2pgmL-1, respectively, lower than commercial ELISA kits and reported SERS-LFA detection system-based Au NPs and Fe3O4@3nm Au MNPs. This magnetic SERS-LFA also showed high performance of multi-variant strain detection and further distinguished clinical samples of Omicron variant infection, demonstrating the potential of in situ detection of respiratory virus diseases.

Transient Mild Photothermia Improves Therapeutic Performance of Oral Nanomedicines with Enhanced Accumulation in the Colitis Mucosa.

The treatment outcomes of oral medications against ulcerative colitis (UC) have long been restricted by low drug accumulation in the colitis mucosa and subsequent unsatisfactory therapeutic efficacy. Here, high-performance pluronic F127 (P127)-modified gold shell (AuS)-polymeric core nanotherapeutics loading with curcumin (CUR) is constructed. Under near-infrared irradiation, the resultant P127-AuS@CURs generate transient mild photothermia (TMP; ≈42°C, 10 min), which facilitates their penetration through colonic mucus and favors multiple cellular processes, including cell internalization, lysosomal escape, and controlled CUR release. This strategy relieves intracellular oxidative stress, improves wound healing, and reduces immune responses by polarizing the proinflammatory M1-type macrophages to the anti-inflammatory M2-type. Upon oral administration of hydrogel-encapsulating P127-AuS@CURs plus intestinal intralumen TMP, their therapeutic effects against acute and chronic UC are demonstrated to be superior to those of a widely used clinical drug, dexamethasone. The treatment of P127-AuS@CURs (+ TMP) elevates the proportions of beneficial bacteria (e.g., Lactobacillus and Lachnospiraceae), whose metabolites can also mitigate colitis symptoms by regulating genes associated with antioxidation, anti-inflammation, and wound healing. Overall, the intestinal intralumen TMP offers a promising approach to enhance the therapeutic outcomes of noninvasive medicines against UC.

Magneto-photothermal synergy applied to gold-coated magnetic nanoparticles

In this work, we describe the synthesis of magnetic nanoparticles with a suitable size for easy cellular internalization, avoiding their rapid renal excretion (less than 5 nm) and accumulation in the liver (more than 100 nm). The nanoparticles are functionalized with a biocompatible polymer (low molecular weight, branched polyethylenimine, PEI), and this treatment allows their functionalization with a shell of gold particles in order to improve their ability to absorb electromagnetic radiation in the visible and near infrared wavelength regions. As a result, the magnetic nanostructures are potential agents of local heating (hyperthermia) by exposing them to alternating magnetic fields (magnetic hyperthermia) or to light of the suitable wavelength (photothermia). Magnetic hyperthermia experiments demonstrate that both types of particles can reach the desired temperature range for cell apoptosis, with the difference of a shorter time needed when gold is absent. The released thermal energy is measured by the SAR (specific absorption rate, in W/g), and the values found are promising, up to 600 W/g in the case of uncoated particles. Regarding the photothermia response under the IR radiation, it is comparable for gold-coated and uncoated magnetic particles, but it is enhanced by a factor of almost 10 when the incident light is visible (blue-green) and the particles are provided with their gold shell. Improvements related to the selection of gold particles with resonant absorbance in the infrared are under investigation.

Synthesis of trimetallic iron-boron core and gold shell nanoparticles for experimental cancer radiotherapy.

Cancer is a significant and constantly growing clinical problem all over the word. For many types of cancer there has been little change in mortality rate of CRC in the past decades and treatment options are limited. A striking example is malignant Glioblastoma (GBM) which exhibits a high degree of infiltration of surrounding healthy brain tissue, extremely high mortality rate, morbidity and most life-years lost of any cancer. Considerable research efforts in the last several decades have failed to improve these outcomes. Boron Capture Neutron Therapy (BNCT) is an experimental radiotherapy (RT) that shows the best hope for the patients for whom all current therapies fail. BNCT involves the intracellular release of alpha and Li-ion particles from boron in response to neutron beam and therefore its success is critically dependent on achieving high intracellular concentrations of boron atoms within the cancerous cells. Boron phenylalanine (BPA) is the most used compound to deliver boron atoms, but achieving high intracellular concentration of BPA is difficult with this small molecule compound and is an absolute limiting factor for the better outcome of BNCT. Our approach focused on a delivery of a high and stable concentration of boron atoms in a form of novel trimetallic core-shell nanoparticles, combining boron for BNCT and iron for magnetic targeting in the core, and a gold shell for stability and attachment of targeting therapeutic peptides. The research was targeted towards comparing different synthesis variables to form these core-shell particles and incorporate as much boron into the core as possible via redox-transmetalation. Partial gold shells were formed around the core via island growth with a molar ratio of Fe/B of 0.64 and high incorporation of boron.

Controllable synthesis of multi-tip spatial gold nanostructures to facilitate SPR enhancement for exosomal PD-L1 assay

A surface plasmon resonance (SPR) biosensor was developed utilizing gold nanoflowers with multi-tip tiny petals (Au@Au mNFs) and multifunctional peptides for the selective detection of exosomal programmed cell death 1 ligand 1 (ExoPD-L1). In the presence of different salt concentrations, DNA-functionalized gold seeds underwent in situ gold growth, resulting in Au@Au NFs with varying numbers of petals or Au@Au nanospheres (Au@Au NSs). The growth orientation of the gold shells was influenced by the “upright”, “tilted” or “lying” state of the DNA on the gold core surface, depending on the salt concentration solution. The finally prepared Au@Au mNFs exhibited a multi-tip spatial structure, which served as a highly efficient SPR sensitized layer with abundant hot spots on the gold film surface. The enhanced SPR sensitivity was attributed to the substantial electromagnetic field enhancement generated at the tips of the mNFs. By achieving suitable surface coverage of the multifunctional peptide at the sensing interface constructed by Au@Au mNFs, efficient capture of ExoPD-L1 was ensured. The analysis results demonstrated that the developed SPR sensor successfully detected ExoPD-L1 within a concentration range of 10–107 particles/mL, with a detection limit of 4.95 particles/mL. This work highlights the significant improvement in SPR sensing and detection performance achieved by utilizing Au@Au mNFs with multi-tip spatial nanostructures, providing a straightforward approach for achieving ultra-sensitive detection of target substances through SPR.

Efficient Analysis of Small Molecules via Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (LDI-TOF MS) Using Gold Nanoshells with Nanogaps.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a commonly used technique for analyzing large biomolecules. However, the utilization of organic matrices limits the small-molecule analysis because of the interferences in the low-mass region and the reproducibility issues. To overcome these limitations, a surface-assisted laser desorption/ionization (SALDI), which utilizes nanostructured metallic surfaces, has been developed. Herein, a novel approach for SALDI-MS was proposed using silica@gold core-shell hybrid materials with a nanogap-rich shell (SiO2@Au NGS), which is an emerging material due to its excellent heat-generating capabilities. The gold shell thickness was controlled by adjusting the concentration of gold precursor for the growth of gold nanoparticles. SALDI-MS measurements were performed on a layer formed by drop-casting a mixture of SiO2@Au NGS and analytes. At the optimized process, the gold shell thickness was observed to be 17.2 nm, which showed the highest absorbance. Based on the enhanced SALDI capability, SiO2@Au NGS was utilized to detect various small molecules, including amino acids, sugars, and flavonoids, and the ionization softness was confirmed with a survival yield upon fragmentation. The limits of detection, reproducibility, and salt tolerance of SiO2@Au NGS demonstrate its potential as an effective and reliable SALDI material for small-molecule analyses.

Influence of spatial dispersion in metal on optical characteristics of a magnetoplasmonic layered nanoparticle cluster

In the current work, the diffraction problem of a plane electromagnetic wave on a cluster of two layered nanocylinders consisting of a magnetoplasmonic core and a gold shell is considered. The arising effects of spatial dispersion in the gold shell are taken into account within the framework of the generalized nonlocal optical response theory. Based on the discrete source method scheme, an analysis of the influence of the mutual arrangement of particles, their deformation, and the effect of spatial dispersion on the behaviour of the absorption cross-section and the near-field enhancement factor is conducted. It is shown that the position of the plasmon resonance can be shifted to the transparency region of biological tissues by varying the distance between particles and the core material. It has been established that taking into account spatial dispersion in the gold shell leads to a decrease in intensity and a slight shift of the plasmon resonance position to the shortwave region, without going beyond the tissue transparency region.

Synthesis gold and jade type core shell structure Pt@Sn in deboronated MWW zeolite and its good performance for light alkane dehydrogenation

The Pt@Sn core–shell structure was generated in MWW zeolite catalysts prepared by atom-planting incorporated Sn and deposition–precipitation (DP) loaded Pt for direct dehydrogenation of ethane or propane and CO2 oxidative dehydrogenation. The introduced Sn species can immobilize cubic structure Pt nanoparticle with well dispersed particles by DP method through the charge’s attraction. The stronger charge transfer between Pt-Sn improves the catalyst activity for the C-H band breaking of alkane. The zeolite skeleton incoporated Sn formed Sn-O-Si bond and can be broken to be extracted from the zeolite structure as SnO2 under the dehydrogenation process. The extracted SnO2 in the ‘half-cup’ external supercage encapsulates the Pt nanoparticle and forms the gold and jade type core–shell structure, which reduces the Pt agglomeration and modifies the Pt nanoparticle crystal edge and corner active sites and reduced the C-C band cleavage to side products and coke formation, thus improving the dehydrogenation selectivity and stability.

Thermal-Induced Convective Flow around Core–Shell Gold Nanodimers under Continuous-Wave Laser Irradiation: Implications for Nanofluidics

Thermal-Induced Convective Flow around Core–Shell Gold Nanodimers under Continuous-Wave Laser Irradiation: Implications for Nanofluidics

Synthesis and Characterization of Magnetite/Gold Core Shell Nanoparticles Stabilized with a β-Cyclodextrin Nanosponge to Develop a Magneto-Plasmonic System

Magnetite/gold core-shell nanoparticles (magnetite/gold NPs) have important optical and magnetic properties that provide potential for applications, especially biomedical ones. However, their preparation is not exempt from difficulties that might lead to unexpected or undesired structures. This work reports the synthesis and characterization of magnetite/gold NPs using tetramethylammonium hydroxide (TMAH) to promote the formation of a continuous interface between the magnetite core and the thin gold shell. The synthesized magnetite/gold NPs were characterized using transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), field emission scanning electron microscope (FE-SEM), ζ-potential, vibrating sample magnetometer (VSM), selected area electron diffraction (SAED), UV-Visible spectroscopy, and dynamic light scattering (DLS), confirming the core-shell structure of the NPs with narrow size distribution while evidencing its plasmonic and superparamagnetic properties as well. Further, the magnetite/gold NPs were associated and stabilized with a β-cyclodextrin nanosponge (β-CDNSs), obtaining a versatile magneto-plasmonic system for potential applications in the encapsulation and controlled release of drugs.

The Importance of Preventive Analysis in Heritage Science: MA-XRF Supporting the Restoration of Madonna with Child by Mantegna

The Madonna with Child by Andrea Mantegna owned by the Museo Poldi Pezzoli in Milan is painted on canvas with an unusual distemper technique. During the period of 1863–1865, the painting was restored by Giuseppe Molteni. The identification of potential retouchings by Molteni, possibly covering part of the original layer, was the object of this work carried at the Opificio delle Pietre Dure. To evaluate the extent of both Molteni’s intervention and Mantegna’s original layer, the MA-XRF spectrometer developed by CHNet-INFN was used to discriminate between the two paint layers and identify the materials and the extension of both “artists”. Indeed, the elemental maps showed that Molteni’s work entirely covered the mantle of the Virgin, even changing the fold of the draperies and enriching the red robe with shell gold highlights, giving a different appearance to the painting. Moreover, MA-XRF also revealed that the original Mantegna was still mostly intact underneath Molteni’s layer, thereby providing a decisive guide for conservation works. These results indeed formed the basis for the technical decision to remove the varnish and Molteni’s version, unveiling the original Mantegna. A second MA-XRF campaign was then carried out to fully characterise the materials of this unusual painting technique.

The Photothermal Effect of a Single Gold-magnetic Nanocrescent in A Glycerol-water Mixture Media

The photothermal effect of gold nanostructures has been majority known as the nanothermal effect of gold clusters under laser irradiation. However, there are still many challenges to measuring the local temperature generated by a single nano gold in a complex media. In this work, a gold magnetic nanocrescent (G-MNC) has been studied, it composed of a superparamagnetic iron oxide core and gold shell with a size of 170 nm in glycerol/water (80:20), under 650 nm laser irradiation. Using rotational scattering correlation spectroscopy (RSCS), a sophisticated technique has been developed, the local temperature generated by only single magnetic nanocrescent was measured. The dependence of the heat generation according to the power of the laser shows that the heat generated by the gold NC is proportional to the power of the laser, and the maximum temperature was 19.5 oC, corresponding to the laser power was 29×103 W.cm-2. Under using the proper laser irradiation to the plasmon resonance, G-MNCs act as nano thermometers. The photothermal effect of the single G-MNC was implemented in a mixing solution of glycerol and water.