Synthesis of monodispersed palladium nanoparticles using tannic acid and its optical non-linearity

Tannic acid modified microscale zero valent iron (TA-mZVI) with enhanced anti-passivation capability for Cr(VI) removal

The removal of Cr(VI) from aqueous solutions using microscale zerovalent iron (mZVI) shows promising potential. However, the surface passivation of mZVI particles hinders its widespread application. In this study, we prepared tannic acid (TA) modified mZVI composite (TA-mZVI) by a simple sonication method. The introduction of TA allowing TA-mZVI composite to adsorb Cr(VI) rapidly under electrostatic forces attraction, guarantying TA-mZVI exhibited remarkable Cr(VI) removal capacity with a maximum adsorption capacity of 106.1 mg⋅g-1. At an initial pH of 3, it achieved a rapid removal efficiency of 96.2% within just 5 min, which was 7.7 times higher than that of mZVI. Various characterizations, including XPS and CV analysis, indicated that the formation of TA-Fe complexes accelerates electron transfer. In addition, TA endows functional groups to TA-mZVI, raising the dispersion and stability and serves as a protective layer hindering passivation. Further mechanistic analysis revealed that Cr(VI) removal by TA-mZVI followed an adsorption-reduction-precipitation mechanism, with TA mitigating the surface passivation of mZVI and facilitating the reduction of most Cr(VI) to Cr(III). Batch cyclic experiments revealed that TA-mZVI exhibited satisfactory performance, maintaining over 85% Cr(VI) removal even after five cycles and minimally affected by various coexisting ions. With notable advantages in cost-effectiveness, ease-synthesis and recovery, this work provides a great promise for developing efficient reactive adsorbent for addressing Cr(VI) contamination in aqueous solutions.

High-loading Cu single-atom nanozymes supported by carbon nitride with peroxidase-like activity for the colorimetric detection of tannic acid

The design of nanozymes with high metal atom loading is of great significance to improve enzyme activity and is also the key to furthering the construction of highly sensitive colorimetric sensors. In this work, a colorimetric sensor for the quantitative analysis of tannic acid (TA) was developed based on two-dimensional carbon nanosheet carbon nitride (CN)-supported Cu single-atom nanozymes (Cu/CN). Cu/CN was synthesized by supramolecular preorganization and calcination, with an ultrathin nanosheet structure and a high density of Cu active sites, with a Cu loading of up to 14.3 wt%. Benefiting from the above characteristics, Cu/CN exhibits peroxidase-mimicking activity and excellent catalytic performance. Therefore, a colorimetric sensor was constructed for the fast and sensitive quantitative analysis of TA with good linearity in the range of 0.09-3.2 μM and a low detection limit of 30 nM. Furthermore, the sensor was successfully applied to the analysis of TA in tea samples of different varieties. This work sheds new light on the design of nanozymes with a high density of active sites and the analysis of TA in real environments.

Synthesis methods and applications of palladium nanoparticles: A review

Palladium (Pd) is a key component of many catalysts. Nanoparticles (NPs) offer a larger surface area than bulk materials, and with Pd cost increasing 5-fold in the last 10 years, Pd NPs are in increasing demand. Due to novel or enhanced physicochemical properties that Pd NPs exhibit at the nanoscale, Pd NPs have a wide range of applications not only in chemical catalysis, but also for example in hydrogen sensing and storage, and in medicine in photothermal, antibacterial, and anticancer therapies. Pd NPs, on the industrial scale, are currently synthesized using various chemical and physical methods. The physical methods require energy-intensive processes that include maintaining high temperatures and/or pressure. The chemical methods usually involve harmful solvents, hazardous reducing or stabilizing agents, or produce toxic pollutants and by-products. Lately, more environmentally friendly approaches for the synthesis of Pd NPs have emerged. These new approaches are based on the use of the reducing ability of phytochemicals and other biomolecules to chemically reduce Pd ions and form NPs. In this review, we describe the common physical and chemical methods used for the synthesis of Pd NPs and compare them to the plant- and bacteria-mediated biogenic synthesis methods. As size and shape determine many of the unique properties of Pd NPs on the nanoscale, special emphasis is given to the control of these parameters, clarifying how they impact current and future applications of this exciting nanomaterial.

Reductive immobilization of Cr(VI) in contaminated water by tannic acid

The rapid reductive immobilization of Cr(VI) from the aqueous solution was achieved by reduction to Cr(III) using tannic acid (TA), and subsequent pH-triggering precipitation of the organo-Cr(III) complexes formed in the redox reaction. The effects of TA concentration, temperature, and solution pH on the reduction of Cr(VI) were examined by batch experiments, and the rapid redox reduction followed a second-order kinetics with respect to Cr(VI) concentration in the pH range of 2.0-3.0. UV-visible spectra, FTIR, and XPS confirmed the complete detoxification of Cr(VI) concomitant with carboxylation of partial phenolic hydroxyls in TA. Synchronously, the reduced Cr(III) coordinated with carboxyl groups in oxidized TA (OTA) to form complexes, which exhibited remarkable pH-dependent size distribution characteristics as illustrated by SEM images and sequential filtration/ultrafiltration. The resulted Cr(III) complexes could aggregate into colloids with larger size and precipitate out at pH range of 6.0-8.0 via cross-linking, thereby leading to 93% Cr and 89% TOC immobilization. An eco-friendly and cost-effective method for Cr(VI) elimination and immobilization is provided because polyphenols are natural polymers derived from plants.

Sono-Biosynthesis and Characterization of AuNPs from Danube Delta Nymphaea alba Root Extracts and Their Biological Properties

Root extracts from Danube Delta Nymphaea alba were used to prepare gold nanoparticles (AuNPRn) by reducing HAuCl4 at different pHs (6.4-8.4) using ultrasonic irradiation: an easy, cheap, eco-friendly and green approach. Their antibacterial and anticancer activities were evaluated against Staphylococcus aureus and Escherichia coli, and A2780 ovarian cancer cells, respectively. The AuNPRn were characterized concerning their phytoconstituents (polyphenols, flavonoids and condensed tannins) and gold content. All of the nanoparticles were negatively charged. AuNPRn exhibited a hydrodynamic size distribution ranging from 32 nm to 280 nm, with the larger nanoparticles being obtained with an Au/root extract ratio of 0.56, pH 7 and 10 min of sonication (AuNPR1), whereas the smallest were obtained with an Au/root extract ratio of 0.24, pH 7.8 and 40 min of sonication (AuNPR4). The TEM/SEM images showed that the AuNPRn had different shapes. The ATR-FTIR indicated that AuNPRn interact mainly with hydroxyl groups present in the polyphenol compounds, which also confirm their high antioxidant capacity, except for AuNPR2 obtained at pH 6.4. Among the AuNPRn, the smallest ones exhibited enhanced antimicrobial and anticancer activities.

Applications of tannic acid in membrane technologies: A review

Today, membrane technologies play a big role in chemical industry, especially in separation engineering. Tannic acid, one of the most famous polyphenols, has attracted widespread interest in membrane society. In the past several years, researches on the applications of tannic acid in membrane technologies have grown rapidly. However, there has been lack of a comprehensive review for now. Here, we summarize the recent developments in this field for the first time. We comb the history of tannic acid and introduce the properties of tannic acid firstly, and then we turn our focus onto the applications of membrane surface modification, interlayers and selective layers construction and mixed matrix membrane development. In those previous works, tannic acid has been demonstrated to be capable of making a great contribution to the membrane science and technology. Especially in membrane surface/interface engineering (such as the construction of superhydrophilic and antifouling surfaces and polymer/nanoparticle interfaces with high compatibility) and development of thin film composite membranes with high permselectivity (such as developing thin film composite membranes with ultrahigh flux and high rejection), tannic acid can play a positive and great role. Despite this, there are still many critical challenges lying ahead. We believe that more exciting progress will be made in addressing these challenges in the future.

Photochemically Enhanced Selective Adsorption of Gold Ions on Tannin-Coated Porous Polymer Microspheres

Metal recovery from electronic waste and industrial wastewater has attracted increasing attention to recycle precious metals and inhibit the emission of hazardous heavy metals. However, the selective recovery of precious metals with a large quantity is still very challenging because wastewater contains a variety of different cations while precious metal ions are relatively scarce. Here, we introduce a simple method to selectively increase the adsorption of gold ions using tannin-coated porous polymer microspheres through photochemical reduction. Mesoporous poly(ethylene glycol dimethacrylate- co-acrylonitrile) microspheres with an average pore diameter of 13.8 nm were synthesized and used as an adsorbent matrix. Tannic acid (TA) was deposited onto the internal pores of the polymer matrix by simple immersion in an aqueous milieu. TA coatings increased the maximum number of adsorbed gold ions by 1.3 times because of the well-known metal ion chelation of TA. Under light illumination, the maximum number of adsorbed gold ions dramatically increased by 6.1 times. We examined two distinct mechanisms presumably involved in the enhanced adsorption: the photooxidation of TA and plasmon-induced hot electrons. Moreover, TA-coated microspheres exhibited remarkable selectivity for gold ions among competing metal ions commonly found in waste resources. This work suggests that the photochemically activated TA can serve as an excellent adsorbent for the selective and efficient recovery of gold ions from wastewater.

Bio-synthesis of palladium nanocubes and their electrocatalytic properties

The bio-synthesis of palladium nanocubes (PdNCs) was realised using pine needle extract as the reducing agent and cetyl trimethyl ammonium bromide as the capping agent. As an eco-friendly and readily available biomass, pine needle extract avoided the use of highly polluting chemical reducing agents. The growth process of PdNCs was analysed using ultraviolet-vis and Fourier transform infrared spectroscopy. Flavonoids, esters, terpenoids and polyhydric alcohols, which contain reductive groups, were mainly responsible for the transition of Pd2+ ions to PdNCs. The morphology and structure of PdNCs were characterised using transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction and X-ray diffraction. It was indicated that the as-prepared PdNCs displayed a relatively high purity and good crystallinity with a face-centred cubic structure and exhibited sizes ranging from 6.11 to 29.51 nm with an average particle size of 11.18 nm. In the methanol electro-oxidation reaction, the PdNCs enclosed by {100} facets exhibited superior electro-catalytic activity to commercial Pd/C, which was rarely reported in other bio-synthesis processes for Pd catalysts. Meanwhile, the PdNCs showed excellent anti-poisoning ability and long-term stability. This study reveals the possibility of preparing shape-controlled PdNCs with a specific structure and excellent electro-catalytic activity.

Morphology dependent catalysis and surface enhanced Raman scattering (SERS) studies using Pd nanostructures in DNA, CTAB and PVA scaffolds

Palladium nanoparticles (Pd NPs) of three different morphologies viz., nanocubes with cetyltrimethylammonium bromide (CTAB), nanowires with polyvinyl alcohol (PVA) and Pd NPs with deoxyribonucleic acid (DNA) scaffolds were synthesized by UV-irradiation. Catalysis and surface enhanced Raman scattering (SERS) studies were done with the synthesized morphologically distinct Pd nanostructures for the very first time. The catalytic rate was extremely high with Pd nanowires templated with PVA and the order of the catalytic rate was Pd nanowires in PVA > Pd nanocubes in CTAB > DNA-Pd wire-like assemblies. The highest catalytic rate was observed for PVA capped Pd nanowires which is a few hundred fold higher than other metal NP catalysts. Methylene blue (MB) was used as a Raman analyte for the SERS study and the largest EF of 1.9 × 10⁵ at a peak position of 1391 cm^-1 was observed with Pd nanowires in the DNA scaffold as a SERS substrate. The order of the SERS EF values was DNA-Pd wire-like assemblies > Pd nanocubes in CTAB > Pd nanowires in PVA. Beyond everything, the present synthesis route is easy, faster, candid, highly reproducible and cost-effective. In the near future, the same protocol could be applied to synthesize other materials for various applications.

Silver and gold nanoparticles from tannic acid: synthesis, characterization and evaluation of antileishmanial and cytotoxic activities

Gold (Au0) and silver (Ag0) nanoparticles were synthesized using tannic acid (TA) as both reducing and stabilizer. Nanoparticles formation, stability, and interaction with TA were compared to citrate-coated nanoparticles and monitored by UV-Vis, zeta potential, and transmission electron microscopy. TA coating resulted in a red-shift and broadening of bands compared to citrate-coated nanoparticles (NPs-Cit). AgNPs-TA and AuNPs-TA are negatively charged with mean surface charge of -29.4 mV and -29.6 mV, respectively. TEM images showed polydispersety of AuNPs-TA (6-42 nm) and aggregation of AgNPs-TA (12-71 nm). In vitro assays of Leishmania amazonensis promastigotes showed an increment of antileishmanial activity for AgNPs-TA in relation to AgNPs-Cit, while AuNPs-TA and AuNPs-Cit did not affect the protozoas at tested concentrations. CC50 value for AgNPs-TA suggested that TA attenuates nanosilver toxicity comparatively to its precursor (Ag+). This investigation can contribute to the development of new, green, and fast produced drugs aiming at leishmaniasis treatment.

Toxicity studies of nanofabricated palladium against filariasis and malaria vectors

The present study was carried out to establish the biofabrication of palladium nanoparticles (PdNPs) using the plant leaf extract of Tinospora cordifolia Miers and its toxicity studies on the larvae of filariasis vector, Culex quinquefasciatus Say and malaria vector, Anopheles subpictus Grassi. The biofabricated PdNPs were characterized by using UV-visible spectrum, FTIR, XRD, FESEM, EDX and HRTEM. HRTEM confirmed the PdNPs were slightly agglomerated and spherical in shape and the average size was 16 nm. Gas chromatography and mass spectrometry analysis result revealed that the major constituent present in the T. cordifolia leaf extract is 2,4-di-tert-butylphenol (31.79%) whereas the minor compounds are 1-hexadecanol (7.97%), 1-octadecanol (7.70%), 1-eicosanol (6.85%), behenic alcohol (5.36%), 1-tetradecene (6.22%), cyclotetradecane (6.23%), 1-hexadecene (7.97%), 1-octadecene (7.70%), 1-eicosene (6.85%), and 1-docosene (5.36%). T. cordifolia leaf extract exhibited the larvicidal activity against the fourth instar larvae of C. quinquefasciatus and A. subpictus with the values of LC₅₀ = 59.857 and 54.536 mg/L; LC₉₀ = 113.445 and 108.940 mg/L, respectively. The highest toxicity was observed in the biofabricated PdNPs against the fourth instar larvae of C. quinquefasciatus and A. subpictus with the values of LC₅₀ = 6.090 and 6.454 mg/L; LC₉₀ = 13.689 and 13.849 mg/L, respectively. Concerning non-target effects, Poecilia reticulata were exposed to PdNPs for 24 h and did not exhibit any noticeable toxicity. Overall, our findings strongly suggest that PdNPs is a perfect ecological and inexpensive approach for the control of filariasis and malaria vectors.

Sapium sebiferum leaf extract mediated synthesis of palladium nanoparticles and in vitro investigation of their bacterial and photocatalytic activities

There is a growing need to introduce eco-friendly and sustainable procedures for the synthesis of metal nanoparticles that include a mild reaction conditions, simple reaction setup, use of nontoxic medium such as water and plant extract, cost effectiveness as well as greater efficiency for biomedical and catalytic applications. For this purpose, small and highly dispersed palladium nanoparticles (PdNPs) were prepared by eco-friendly and cost effective green method using water soluble leaf extract of Sapium sebiferum as a reducing and capping agent. The formation of PdNPs was optimized at various temperatures i.e. (30°C, 60°C and 90°C) and different leaves extract (5mL and 10mL) in order to control their size and shape. The results indicated that PdNPs synthesized at 10mL leaf extract concentration and 60°C temperature have small sized (5nm) and spherical shape. The nanoparticles formation, their dispersion, size and shape were confirmed by various characterization techniques i.e. UV-Vis spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), thermo gravimetric analysis (TGA) and Dynamic light scattering technique (DLS) analysis. The biologically synthesized PdNPs were tested for size dependent photo degradation of methylene blue and inactivation of bacteria. The PdNPs synthesized at optimized condition (10mL extract concentration and 60°C) have strong photo catalytic activity and reduced 90% methylene blue in 70min. The optimized PdNPs also showed strong bacterial inhibition against Staphylococcus aureus 29(±0.8mm), Bacillus subtilis 19(±0.6mm) and pseudomonas aeruginosa 11(±0.6mm). The results of this examination demonstrate effective applications of extremely active PdNPs.

Nature-Inspired One-Step Green Procedure for Enhancing the Antibacterial and Antioxidant Behavior of a Chitin Film: Controlled Interfacial Assembly of Tannic Acid onto a Chitin Film

The final goal of this study was to develop antimicrobial food-contact materials based on a natural phenolic compound (tannic acid) and chitin, which is the second most abundant polysaccharide on earth, using an interfacial assembly approach. Chitin film has poor antibacterial and antioxidant ability, which limits its application in industrial fields such as active packaging. Therefore, in this study, a novel one-step green procedure was applied to introduce antibacterial and antioxidant properties into a chitin film simultaneously by incorporation of tannic acid into the chitin film through interfacial assembly. The antibacterial and antioxidant behavior of chitin film has been greatly enhanced. Hydrogen bonds and hydrophobic interaction were found to be the main driving forces for interfacial assembly. Therefore, controlled interfacial assembly of tannic acid onto a chitin film demonstrated a good way to develop functional materials that can be potentially applied in industry.

Coordination-driven multilayer of phosvitin-polyphenol functional nanofibrous membranes: antioxidant and biomineralization applications for tissue engineering

The layer-by-layer (LBL) deposition technique has been widely used to decorate the nanofibers formed from polymer pairs with complementary functional groups.

Biodirected synthesis of palladium nanoparticles using Phoenix dactylifera leaves extract and their size dependent biomedical and catalytic applications

Graphical representation of green synthesis of PdNPs and their biological and catalytic applications.

Antiplasmodial activity of eco-friendly synthesized palladium nanoparticles using Eclipta prostrata extract against Plasmodium berghei in Swiss albino mice

Malaria is an infectious disease caused by the Plasmodium parasite that continues to be a health issue for humans. It is one of the most common pathogenic factors of morbidity and mortality. Palladium nanoparticles (Pd NPs) have been used as target antimicrobial compounds, as a catalyst to manufacture pharmaceuticals, degrade harmful environmental pollutants, and as sensors for the detection of various analyses. The aim of this study was to investigate the antiplasmodial activity of synthesized Pd NPs by using leaf aqueous extract of Eclipta prostrata against Plasmodium berghei in Swiss albino mice. The synthesized Pd NPs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Scanning electron microscopy (SEM) with Energy dispersive X-ray spectroscopy (EDX), and High-resolution transmission electron microscope (HRTEM) with the Selected area (electron) diffraction (SAED). The XRD peaks appeared at 35.61°, 44.27°, 56.40°, and 74.51°, which correspond to (111), (200), (220), and (311) planes for palladium, respectively. The FTIR spectra that were carried out to identify the potential biomolecule of synthesized Pd NPs showed the peaks at 3361, 1540, 1399, 1257, 1049, and 659 in the region of 4000-500 cm(-1). The SEM images showed aggregation of NPs with an average size of 63 ± 1.4. The HRTEM images of the precipitated solid phase obtained after termination of the reaction of E. prostrata aqueous leaf extract were in the range from 18 to 64 nm with an average size of 27 ± 1.3 nm. The in vivo antiplasmodial assay was carried out as per Peters' 4-day suppressive test, and the synthesized Pd NP-treated mice group showed reduction of parasitemia by 78.13% with an inhibitory concentration (IC)50 value of 16.44 mg/kg/body weight. The growth inhibition of E. prostrata aqueous leaf extract, palladium acetate, and synthesized Pd NPs showed the IC20, IC50, and IC90 values of 1.90, 10.29, and 64.11; 4.49, 9.84, and 23.04; and 4.34, 8.70, and 18.49 mg/kg/body weight, respectively against NK65 strain of P. berghei. In vitro cytotoxicity of the aqueous leaf extract of E. prostrata, palladium acetate, and Pd NPs that was evaluated against Hep-G2 cell lines showed the cellular toxicity of 7.5, 12, 22, 32, and 39%; 8.2, 18, 32, 55, and 66.2 %; and 8.5, 24, 48, 65, and 76.5% at 1, 10, 100, 250, and 500 μg/mL, respectively. This green chemistry approach toward the synthesis of Pd NPs has many advantages such as, ease with which the process can be scaled up, and economic viability.

In situ synthesis of gold nanoparticles on LBL coated nanofibers by tannic acid for catalytic application

Electrospinning nanofibrous mats are extensively studied as efficient two-dimensional nanomaterials and applied in the fields of filtration, catalysis, and biosensors due to their flexibility and porosity.

Very fast catalytic reduction of 4-nitrophenol, methylene blue and eosin Y in natural waters using green chemistry: p(tannic acid)–Cu ionic liquid composites

Using tannic acid (TA) as a biopolymer, poly(tannic Acid) (p(TA)) microgels were obtained by cross-linking TA with trimethylolpropane triglycidyl ether (TMPGDE) as cross-linker in a water-in-oil micro emulsion system.

Reviewing the Tannic Acid Mediated Synthesis of Metal Nanoparticles

Metal nanoparticles harbour numerous exceptional physiochemical properties absolutely different from those of bulk metal as a function of their extremely small size and large superficial area to volume. Naked metal nanoparticles are synthesized by various physical and chemical methods. Chemical methods involving metal salt reduction in solution enjoy an extra edge over other protocols owing to their relative facileness and capability of controlling particle size along with the attribute of surface tailoring. Although chemical methods are the easiest, they are marred by the use of hazardous chemicals such as borohydrides. This has led to inclination of scientific community towards eco-friendly agents for the reduction of metal salts to form nanoparticles. Tannic acid, a plant derived polyphenolic compound, is one such agent which embodies characteristics of being harmless and environmentally friendly combined with being a good reducing and stabilizing agent. In this review, first various methods used to prepare metal nanoparticles are highlighted and further tannic acid mediated synthesis of metal nanoparticles is emphasized. This review brings forth the most recent findings on this issue.

Vacuum-assisted layer-by-layer electrospun membranes: antibacterial and antioxidative applications

Layer-by-layer assembled films have been exploited for functional materials.