Deposition Of Ag Nanoparticles Research Articles

Strategies for Metallizing and Electroplating Biodegradable PLA

With environmental awareness in societies, bioplastics continue to receive increasing attention and utilization rate. Polylactic acid (PLA) is one of the most important biopolymers in the market today, owing to its high strength and relative ease of forming. Unlike the common structural, fossil fuel-based plastics, such as Acrylonitrile-Butadiene-Styrene (ABS), the surface of PLA cannot be readily metallized in preparation for electroplating using the conventional plating-on-plastic (POP) process. This partially limits the wider use of the material for functional and decorative applications. In this research study, we systematically explored three strategies for metallizing the surface of PLA, namely, (A) chemical etching and palladium activation technique, (B) polyelectrolyte multilayers (PEMs) and Ag nanoparticle deposition technique, and (C) Ag conductive painting technique. PLA samples, prepared by Fused Deposition Modelling (FDM) 3D-printing technique, were metallized by various techniques followed by electroless deposition and electroplating of copper layers. The study was performed comparatively with respect to the ABS surface. The samples microstructures, chemical distributions, and plating characteristics were assessed with optical and scanning electron microscopy. The adhesion of the metallic coatings was analyzed using scratch test and tape test. Although uniform deposition of copper layers on PLA surfaces could be achieved using all three metallizing methods under investigation, the three methods were found to provide different degrees of benefits with respect to deposition rate, surface uniformity, and process simplicity.

Fabrication of Ag nanoparticles decorated hieratical Ni0.25Co0.75(OH)2 microflowers photocatalyst toward efficient environmental remediation

The bimetallic hydroxide NixCo1-x(OH)2 was first prepared through hydrothermal method. The prepared NixCo1-x(OH)2 architecture showed good photocatalytic degradation performance toward oxytetracycline (OTC), especially the Ni0.25Co0.75(OH)2 hierarchical microflowers. After deposition of Ag nanoparticles, Ag/Ni0.25Co0.75(OH)2 nanocomposites with further improved photocatalytic activity were obtained especially on 0.2% Ag/Ni0.25Co0.75(OH)2. The modified band structure with optimal loading amount of Ag nanoparticles was convinced to have positive effect on the efficient photo-induced charge separation and transfer during photocatalytic procedure. This study expanded the application of hydroxides in the field of photocatalysis, and provided ideas for the construction of new photocatalytic system.

An Amphiphilic Carbonaceous/Nanosilver Composite-Incorporated Urinary Catheter for Long-Term Combating Bacteria and Biofilms.

Biofilms formed on urinary catheters remain a major headache in the modern healthcare system. Among the various kinds of biocide-releasing urinary catheters that have been developed to prevent biofilm formation, Ag nanoparticles (AgNPs)-coated catheters are of great promising potential. However, the deposition of AgNPs on the surface of catheters suffers from several inherent shortcomings, such as damage to the urethral mucosa, uncontrollable Ag ion kinetics, and unexpected systematic toxicity. Here, AgNPs-decorated amphiphilic carbonaceous particles (ACPs@AgNPs) with commendable dispersity in solvents of different polarities and broad-spectrum antibacterial activity are first prepared. The resulting ACPs@AgNPs exert good compatibility with silicone rubber, which enables the easy fabrication of urinary catheters using a laboratory-made mold. Therefore, ACPs@AgNPs not only endow the urinary catheter with forceful biocidal activity but also improve its mechanical properties and surface wettability. Hence, the designed urinary catheter possesses excellent capacity to resist bacterial adhesion and biofilm formation both in vitro and in an in vivo rabbit model. Specifically, a long-term antibacterial study highlights its sustainable antibacterial activity. Of note, no obvious toxicity or inflammation in rabbits was triggered by the designed urinary catheter in vivo. Overall, the hybrid urinary catheter may serve as a promising biocide-releasing urinary catheter for antibacterial and antibiofilm applications.

Ag-doped Cobweb-like structure of TiO2 nanotubes for antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA)

Hydrothermal reaction and photodeposition were used to transform TiO2 nanoparticles to TiO2 nanotubes (TNTs) loaded with Ag. The structure and morphology of TNTs and Ag/TNTs were characterized, and the antibacterial activity of all catalysts against Methicillin-resistant S. aureus was tested using agar well diffusion and total viable plate count methods in the absence and presence of UV light. The cobweb-like structure of TNTs was noticed, and the network could increase the surface area to 184–216 m2/g, an up to fourfold increase compared to TiO2 P25. The XRD, EDS, HRTEM and UV-DR results revealed Ag nanoparticle deposition on the TNTs surface. The HRTEM result also showed no change in the shape or morphology of TNTs. The Ag nanoparticle size on the TNTs surface ranged from 8.928 ± 1.487 to 14.654 ± 2.901 nm. The light absorption capacity of TiO2, TNTs, and Ag/TNTs displayed antibacterial activity in the presence of UV light. In contrast, only Ag/TNTs could reduce the bacteria growth in the dark condition, which decreased the restriction of TNTs and TiO2. The maximum antibacterial activity was obtained at 1.5%Ag/TNT, at which the cell viability was 77.86% of the initial number concentration. Based on the result of this research work, it could be confirmed that Ag/TNTs can potentially be used as a disinfection material in both presence as well as absence of UV light.

Representation of Vivid Colors of Cyan, Magenta, Yellow, and Green in Ag Deposition-Based Plasmonic Electrochromic Device By Precise Control of Shape and Density of Deposited Ag Nanoparticles

Ag nanoparticles exhibit various colors depending on their localized surface plasmon resonance (LSPR). Based on this phenomenon, Ag deposition-based electrochromic devices can represent various optical states in a single device such as the three primary colors (cyan, magenta, and yellow), silver mirror, black and transparent.1 A control of the morphology of Ag nanoparticles can lead to dramatic changes in color, as their size and shape influence the LSPR band. For this purpose, the “voltage-step method” was applied to a Ag deposition-based EC device to obtain multiple colors by shifting the LSPR band. In this method, two different voltages are successively applied : the first voltage V 1 is applied for a very short time t 1 to initiate Ag nucleation, and the second voltage V 2 is applied for a time t 2 to promote growth of the Ag nuclei. As V 2 is more positive than the nucleation voltage, further nucleation is no longer possible during t 2. Therefore, the Ag nanoparticle growth and the resultant device color can be controlled by changing t 2.In this study2, we aimed to improve the color quality of Ag deposition-based multicolor EC devices by precisely controlling the supply of Ag+ ions to the electrode surface. Initially, the effect of coloration by decreasing the concentration of Ag+ ions in the Ag deposition-based EC device was investigated. As a result of optimizing the driving voltage, a lower concentration device (10 mM Ag+ ion) showed vivid and bright colors of cyan and magenta. This improvement was due to the generation of fine Ag nanoparticles and the prevention of the connection of Ag particles. From the electrochemical investigation, it was suggested that the slow supply rate of Ag+ ions in the lower concentration device induced electrochemical deposition of fine and isolated Ag nanoparticles.Consequently, to obtain more uniformly deposited Ag nanoparticles, the nucleation voltage of V 1 was set to a lower voltage in the 10 mM device. As a result, spherical Ag nanoparticles were successfully obtained, and the device showed yellow and green colors. By comparing the LSPR behavior of the device with that of Ag nanoparticles dispersed in solution and using FDTD calculations, the mechanism of the yellow and green colors was investigated in detail. Thus, it indicated that the yellow coloration with an absorption band in the 400–500 nm region was caused by LSPR absorption of isolated spherical Ag nanoparticles. Furthermore, it was also observed that the coexistence of isolated spherical particles and aggregations of Ag nanoparticles induced two types of LSPR bands, leading to a good green color. References A.Tsuboi, K.Nakamura and N.Kobayashi, Chem. Mater., 2014, 26, 6477-6485S.Kimura, T.Sugita, K.Nakamura and N. Kobayashi, Nanoscale, 2020 (in press)

Mussel-Inspired Deposition of Ag Nanoparticles on Dopamine-Modified Cotton Fabric and Analysis of its Functional, Mechanical and Dyeing Properties

Mussel-Inspired Deposition of Ag Nanoparticles on Dopamine-Modified Cotton Fabric and Analysis of its Functional, Mechanical and Dyeing Properties

Co-catalyst boosted photocatalytic hydrogen production driven by visible-light over g-C3N4: The synergistic effect between Ag and Ag2S

Developing a co-catalyst structure with a rational design is necessary to improve the photocatalytic performance. In this work, a series of g-C3N4/Ag-Ag2S photocatalysts were prepared by depositing Ag nanoparticles onto g-C3N4 through photoreduction, followed by a partial sulfidation of Ag into Ag2S via a solution method. Various characterizations were employed to investigate the crystal phase, composition, and morphology of the synthesized samples in detail. The evaluation results for photocatalytic H2 production show that g-C3N4/Ag-Ag2S-8 possesses a H2 production rate of 223.5 μmol g−1 h−1 when subjected to a 300 W xenon lamp for 5 h, which far exceeds those of the remaining as-prepared samples. Besides, g-C3N4/Ag-Ag2S-8 also exhibits an acceptable photostability in recycling experiments. Based on multiple measurements on the textural properties, optical properties, charge separation performances, and proton reduction abilities of the as-prepared samples, it is believed that the rapid separation of photogenerated carriers and excellent proton capturing ability caused by the rationally designed Ag-Ag2S co-catalyst are the two key factors that can result in the efficient photocatalytic H2 production observed in g-C3N4/Ag-Ag2S. Furthermore, a plausible mechanism for the photocatalytic H2 production in g-C3N4/Ag-Ag2S is also provided. Thus, this work may provide new insights into the future development of semiconductor composites for photocatalysis.

Electron Donor-Acceptor Effect-Induced Organic/Inorganic Nanohybrids with Low Energy Gap for Highly Efficient Photothermal Therapy.

For the design and optimization of near-infrared photothermal nanohybrids, tailoring the energy gap of nanohybrids plays a crucial role in attaining a satisfactory photothermal therapeutic efficacy for cancer and remains a challenge. Herein, we report an electron donor-acceptor effect-induced organic/inorganic nanohybrid with a low energy gap (denoted as ICG/Ag/LDH) by the in situ deposition of Ag nanoparticles onto the CoAl-LDH surface, followed by the coupling of ICG. A combination study verifies that the supported Ag nanoparticles as the electron donor (D) push electrons into the conjugated system of ICG by the electronic interaction between ICG and Ag, while OH groups of LDHs as the electron acceptor (A) pull electrons from the conjugated system of ICG by hydrogen bonding (N···H-O). This induces the formation of the D-A conjugated π-system and has a strong influence on the π-conjugated system of ICG, thus leading to a prominent decrease toward the energy gap and correspondingly an ultra-long redshift (∼115 nm). The resulting ICG/Ag/LDHs show an enhanced photothermal conversion efficiency (∼45.5%) at 808 nm laser exposure, which is ∼1.6 times larger than that of ICG (∼28.4%). Such a high photothermal performance is attributed to the fact that ICG/Ag/LDHs possess a D-π-A hybrid structure and a resulting lower energy gap, thus effectively promoting nonradiative transitions and leading to enhancement of the photothermal effect. Both in vitro and in vivo results confirm the good biocompatible properties and capability of the ICG/Ag/LDHs for NIR-triggered cancer treatment. This research demonstrates a successful paradigm for the rational design and preparation of new nanohybrids through the modulation of electron donor-acceptor effect, which offers a new avenue to achieve efficient phototherapeutic agent for improving the cancer therapeutic outcomes.

In situ photochemical deposition of Ag nanoparticles on polyester fiber membranes as flexible SERS substrates for sensitive detection of sodium saccharin in soft drinks

Flexible surface-enhanced Raman scattering (SERS) substrates, specifically paper-based SERS substrates, are generally employed in many practical applications. However, paper-based SERS substrate quantitation is still challenging because of the inferior uniformity originating from the irregular morphology of the paper. The present study synthesized Ag nanoparticles (NPs) via the in situ photochemical reduction of Ag+ ions on a titanium dioxide (TiO2) film at the polyester fiber membranes (PFMs) surface. This generated many “hot spots” that presented significant SERS activity with an enhancement factor of 2.1 × 109. Sodium saccharin (SS) bonded to the Ag NPs surface via the carbonyl oxygen and ring nitrogen atoms. A SERS sensor with photochemically deposited Ag NPs was prepared for the sensitive and rapid detection of SS in soft drinks with a limit of detection of 0.3 mg/L. The recovery rate ranged from 93% to 103%, indicating that this method is reliable in actual sample detection with simple pretreatment steps and can be potentially applied for the on-site detection of food additives for food safety.

Rational Construction of Fluorescence Turn-Off Fluorinated Carbon Fiber/Ag Composites and Their Anticancer and Antibacterial Activities.

Although fluorinated carbon fiber/Ag composites possess unique structure and special charge distribution and exhibit great potential in numerous fields, their synthesis has long been a headache because of inert chemistry bonds, low surface energy, and easy aggregation. Herein, we first demonstrate a fresh concept of constructing the nanoscale hydrosoluble fluorinated carbon fiber oxide (FCO)/Ag composite and then integrate it as a highly effective targeting nanocarrier and photothermal therapy and antibacterial agent. Chemical introduction of oxygen allows us to controllably deposit Ag nanoparticles (AgNPs) for the first time and further facilitates surface modification with folic acid prelinked bovine serum albumin to induce targeted endocytosis toward tumor cells. The structure adjustment of FCO into nanosize and the decoration of AgNPs endow the composite with much better photothermal property than fluorinated carbon materials, and FCO/Ag also serves as an effective fluorescence quencher for doxorubicin, realizing visual monitor of drug adsorption processes by "turn-off" fluorescence. Meanwhile, both in vitro and in vivo results reveal greatly improved cancer therapeutic effects than single therapy. What is more is that the synergistic interactions of lipophilic fluorine and AgNPs also ensure highly effective antibacterial activity. Our study integrates FCO/Ag as an emerging drug carrier that exhibits excellent targeted efficiency and high photothemal property and reports its unprecedented experimental example in both antibacterial- and anticancer-combined chemo-photothermal therapy.

BaTiO3 nanocubes/cuboids with selectively deposited Ag nanoparticles: Efficient piezocatalytic degradation and mechanism

The selective deposition of noble metals on catalysts is an attractive modification method for improving catalytic efficiency. However, it is sometimes hard to achieve when facet energies of nano-catalysts show negligible differences. Here, we reported a piezoelectrochemical method which can realize the selective deposition of Ag nanoparticles on the positively polar end of {001}-enclosed BaTiO3 (BTO) nanocubes/cuboids. Furthermore, BTO nanocubes/cuboids with selectively-deposited Ag nanoparticles show approximately 2 times higher piezocatalytic activity than those with randomly-loaded Ag nanoparticles, and much higher than pure BTO nanocubes/cuboids. The piezocatalytic mechanism revealed that the Ag nanoparticles deposited on positively polar end act as “fast lanes” for electrons to transfer to catalysts/solution interfaces, while those loaded on negatively polar end serve as holes trappers hindering ∙OH formation and pollutant degradation. This work confirms an efficient way to improve piezocatalytic performance and provides an insightful discussion of piezocatalytic mechanism.

Electrostatic Interaction-Controlled Formation of Pickering Emulsion for Continuous Flow Catalysis.

Although noble metal or non-noble metal-catalyzed reactions are widely used, it is still difficult to apply these reactions in the large-scale synthesis of chemicals because most of the reactions are carried out by the inefficient batch reaction strategy. Herein, Pickering emulsion-based continuous flow catalysis was utilized to address this problem. Cellulose nanofibers with aldehyde groups (ACNF) were generated through oxidizing C2 and C3 hydroxyl groups of cellulose nanofibers into aldehyde groups by NaIO4, followed by in situ depositing Ag nanoparticles on ACNF to produce Ag-decorated ACNF (ACNF@Ag) via a facile aldehyde-induced reduction method. ACNF@Ag with ∼2 wt % Ag (ACNF@Ag2) has been used to prepare the Pickering emulsion by controlling the electrostatic interaction between ACNF@Ag2 and the oil-water interface via adjusting the pH. It was found that the Pickering emulsion could be generated at a pH around 3.29 and was determined to be the oil-in-water emulsion. The reduction of organic molecules (4-nitrophenol (4-NP), methylene blue (MB), and methyl orange (MO)) was selected as a model reaction to test the reliability of the Pickering emulsion in continuous flow catalysis, which demonstrated very high conversion rates for 4-NP (>98%, 50 h), MB (>99%, 30 h), and MO (>96%, 40 h).

Monitoring and modeling the deposition of metal nanoparticles on surfaces by impedance

The study of metallic nanoparticles (NPs) on surfaces and their properties has become a common subject for a variety of areas. Notably, to exploit the unique intrinsic features of deposited NPs in macroscopic devices, samples with low coverage are required. The electrical characterization techniques have, however, so far been limited to systems near or beyond the percolation limit, when the nanostructure’s resistive behavior is dominant. Here we describe the impedance response of interdigitated electrodes (IDE) during Ag NP deposition, from the very beginning up to the percolation limit. Our experiments present two regimes: up to ~20% of coverage the capacitance grows linearly with the deposition, increasing abruptly afterward. To understand the experimental data, we propose a model in which the capacitance response is attributed to isolated and agglomerated NPs. Initially, isolated NPs contribute to the capacitive response. Beyond ~20% coverage, shielded regions of the IDE due to agglomerated NP islands start to dominate until eventually percolation leads to a predominantly conductive signal. These interpretations are supported by Electron Microscopy and Atomic Force Microscopy. The proposed analysis allows improving the control of the concentration of NP deposited on surfaces systems with low coverage by impedance monitoring.

Free-standing Ag nanoparticle-decorated MoS2 microflowers grown on carbon cloth for photocatalytic oxidation of Rhodamine B

MoS2 microflowers were grown on the surface of a carbon cloth (CC) via a one-step hydrothermal method. Sodium borohydride was used to chemically reduce Ag nanoparticles on the surface of the as-grown MoS2 microflowers. The Ag nanoparticle-decorated MoS2 microflowers grown on the CC (Ag@MoS2/CC) were used for the photocatalytic degradation of rhodamine B (RB) via visible light absorption. The Ag nanoparticles significantly affected the reactivity of the photocatalyst by generating a large number of oxidative radical species. The catalytic reaction followed first-order kinetics and the rate of degradation improved by about 3.3 times upon the deposition of Ag nanoparticles on the surface. Scavenger experiments showed that the hydroxyl radicals generated by the photogenerated electrons were the main contributing species in the degradation of RB. The catalytic mechanism involved efficient electron transfer from the conduction band of MoS2 to Ag through a space charge region, making the surface of the photocatalyst highly electron populated. The fabricated catalyst was highly stable for multiple experiments.

Bandgap Modulation of Glancing Angle Deposition Aided Ag Nanoparticles Covered TiO₂ Thin Film by High Temperature Annealing.

Glancing Angle Deposition (GLAD) technique has been used to fabricate the Ag nanoparticles (NPs) over TiO₂ thin film (TF) on the n-Si substrate. The deposited Ag NPs are in the size of 3-5 nm. Open-air annealing has been done at 500 °C and 600 °C for the n-Si/TiO₂ TF/Ag NP samples. High Resolution X-ray Diffraction (HRXRD) peaks were identified to calculate the crystalline size of the NPs and rutile phase of the annealed sample were exhibited. Morphological analysis has been done for the sample using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS) and Atomic Force Microscopy (AFM). The enhancement of plasmonic absorption and modulation in the bandgap for the annealed Ag NPs surrounded TiO₂ TF has been verified by UV-Vis Spectroscopy and the bandgap has been calculated using Tauc plot. An overall 2.5 fold and 3 fold enhancement has been observed in the UV region and visible region for n-Si/TiO₂ TF/Ag NP annealed at 500 °C and 600 °C samples as compared to the n-Si/TiO₂ TF/Ag NP as-deposited samples. The modulation of bandgap due to the sub-band transition and Localized Surface Plasmon Resonance (LSPR) effect of Ag NPs and relevant sub-band transition due to change in annealing temperature has been reported.

Depositing Ag nanoparticles on g-C3N4 by facile silver mirror reaction for enhanced photocatalytic hydrogen production

In this study, Ag-g-C3N4 composite photocatalysts were prepared by a facile polymerization and silver mirror reaction way. The phase, morphology, chemical structure, electronic and optical properties of the as-prepared photocatalysts were characterized systematically. The photocatalytic performance of Ag-g-C3N4 photocatalysts were evaluated by photocatalytic hydrogen production and the 5% Ag-g-C3N4 exhibited the best hydrogen production rate of 568.9 μmol·g−1·h−1, which is 39 times higher than that of bulk g-C3N4. Subsequently, the photocatalytic mechanism is tentatively proposed. The enhanced photocatalytic activity of Ag-g-C3N4 photocatalysts are ascribed to the efficient utilization of visible light, separation and transportation of the photogenerated charge carriers result from the SPR effect of Ag nanoparticles and Schottky barrier at the interface of Ag and g-C3N4.

Self-assembled deposition of Ag nano-particles on PPy@PEDOT:PSS films to detect melamine molecules

We studied a Surface-enhanced Raman scattering (SERs) film by self-assembled deposition of Ag nanoparticles on the surface of PPy@PEDOT:PSS films to detect melamine molecules. The PPy@PEDOT:PSS film was prepared using an electrochemical polymerization method in a mixture solution of PPy and PEDOT:PSS. Then, Ag nanoparticles were directly deposited on the surface of PPy@PEDOT:PSS films by a chemical self-assembly method as an active SERs substrate to detect melamine molecules. The results showed that the density of Ag nanoparticles on the surface of PPy@PEDOT:PSS film was gradually increased due to the increase of depositional time of Ag nanoparticles. Accordingly, The SERs effect was also substantially enhanced. The signal of melamine was increased up to 440 times. The melamine molecules at 6.4 ng/ml concentration could be clearly identified. This preparing method of SERs film and detecting method of melamine molecules provide a new strategy for the design and application of chemical sensors and bio-sensors.

Study on Glucose Sensing Materials Based on CNT/Graphene-Ag Composite for Nano-Electrode Sensor

Sensors are already part of everyday life, and they are based on a mechanical and electronic pattern such as what humans see, hear and do, and they have a wide range of uses and a wide variety of types. The material that forms a sensor and its structure are very important to perform the sensing role. Electrochemical method is a kind of technology that has been promoted in modern environmental pollutant detection technology. It attracts the attention and interests of many researchers with various advantages. There are many kinds of pollution, and the persistent organic pollutants are especially harmful. Therefore, there is an urgent need to be able to quickly and accurately detect environmental pollution in the in situ method. With the development of nanotechnology, great potential has been created for the design of low-energy consumption, low-cost, high-sensitivity sensors. Due to the properties of carbon nano tube (CNT) and graphene, the combination between C-C and C-C is hexagonal in the nanostructures, which has a great reactivity and are also very stable in high temperature, high pressure, and acid conditions.Carbon Nano Tube (CNT) as nanomaterials have excellent electrical conductivity, high specific surface area and hollow structure, so it can be ideal sensor materials. Based on the excellent properties of the CNT, if the composite material is constructed, this type of material has many new properties at the same time. If such a composite material is used as an electrode, an oxidation-reduction reaction occurs between the contaminant and the electrode, which achieves the purpose of an electrochemical sensor.Synergy effect is achieved by making Metal Nano Composite based on CNT/graphene nanomaterials.These composites have both the characteristics of CNT / graphene and metal, and to make composite with these properties, uniformly plated process and surface treatment technology are required. To manufacture these composite materials, we fabricate Ag-CNT/graphene, optimized the Ag electroless plating (ELP) method for uniform aggregation on CNT/graphene, and optimize the process for the plating solution using the Raman in-situ method. The technique of analyzing the reaction process has been attracting attention from the past. It is very difficult to analyze the process in a chemical reaction because the chemical reaction causes a real-time change in molecular vibration due to a change in binding force. Therefore, there is an urgent need to be able to quickly and accurately detect a chemical reaction in in-situ method. Many electrodes can be formed by electro-less plating (ELP) technique in the sensor process, which enables low-cost and high-efficiency processing. In particular, the greatest advantage of the ELP process is that it can form layers on the nanoscale. In order to uniformly deposit Ag nanoparticles with antimicrobial activity on the surfaces of commercially available nanofilters, it is necessary to process the deposition process in real time and analyze easily.This work mainly studies the application of Multi walled CNT (MWCNT) and MWCNT composite modified electrode in the electrochemical sensor. We aimed to maximize the sensitivity of the sensor by proceeding with silver electroless plating for MWCNT and MWCNT composite. Oxidation of MWCNT showed a stronger plating effect and the pretreatmented MWCNT has a better effect.

Ultrasensitive and reusable SERS probe for the detection of synthetic dyes in food industry through hybrid flower-shaped ZnO@Ag nanostructures

A reliable and accurate sensing of synthetic dyes in foodstuffs is highly significant to prevent health risks. Recently, various heterogeneous structures are used predominantly to explore the distinguished enhancement action of surface-enhanced Raman scattering (SERS) for ultrasensitive detection of multiple food colorants. Herein, we construct a semiconductor/noble-metal heterostructure by deposition of Ag nanoparticles (NPs) on flower-like ZnO microcrystals using a facile photoreduction method. The synergistic effect of flower-like ZnO@Ag nanostructures offers high SERS activity for detection of rhodamine 6G (R6G), sunset yellow (SY), and tartrazine (TZ) with an ultra-low detection limit of 10−12 M, 10−10 M, and 10−11 M, respectively. The flower-like ZnO@Ag nanostructures possess an excellent analytical enhancement factor, sensitivity, and uniformity, towards sensing multiple food colorants. Moreover, the self-reviving ability of the proposed flower-like ZnO@Ag nanostructures is demonstrated by UV-irradiation process and shows its excellent reusability on a single substrate for multiple SERS detection. This work demonstrates the promising use of semiconductor/noble-metal heterostructure with excellent reusability in real-time applications and food safety monitoring.

Gas aggregated Ag nanoparticles as the inorganic matrix for laser desorption/ionization mass spectrometry

We report here on a nanoparticle-assisted laser desorption/ionization time-of-flight mass spectrometry (NP-LDI-TOF MS) for the detection of small molecules. This technique is based on the overcoating of a dried analyte by an array of silver nanoparticles produced by gas aggregation source. This allows for the spatially homogeneous distribution of nanoparticles over the analyte that may fully substitute a conventional organic matrix routinely used for the matrix-assisted laser desorption/ionization mass spectrometry and thus limit the possible interference of matrix with the low-mass molecules. Furthermore, it is shown that the intensity of the detected signal strongly correlates with the number of deposited Ag nanoparticles. At its optimum, that was found to correspond to the nanoparticle surface density of 3x103 NPs.µm−2, the detection limit was 3x10-8 g.L-1 for riboflavin. Such a high detection limit, together with good reproducibility, excellent signal stability, and imaging capability, makes this technique a valuable alternative to other laser desorption/ionization-based detection methods.