Colloidal Substrates Research Articles

A primordial DNA store and compute engine.

Any modern information system is expected to feature a set of primordial features and functions: a substrate stably carrying data; the ability to repeatedly write, read, erase, reload and compute on specific data from that substrate; and the overall ability to execute such functions in a seamless and programmable manner. For nascent molecular information technologies, proof-of-principle realization of this set of primordial capabilities would advance the vision for their continued development. Here we present a DNA-based store and compute engine that captures these primordial capabilities. This system comprises multiple image files encoded into DNA and adsorbed onto ~50-μm-diameter, highly porous, hierarchically branched, colloidal substrate particles comprised of naturally abundant cellulose acetate. Their surface areas are over 200 cm2 mg-1 with binding capacities of over 1012 DNA oligos mg-1, 10 TB mg-1 or 104 TB cm-3. This 'dendricolloid' stably holds DNA files better than bare DNA with an extrapolated ability to be repeatedly lyophilized and rehydrated over 170 times compared with 60 times, respectively. Accelerated ageing studies project half-lives of ~6,000 and 2 million years at 4 °C and -18 °C, respectively. The data can also be erased and replaced, and non-destructive file access is achieved through transcribing from distinct synthetic promoters. The resultant RNA molecules can be directly read via nanopore sequencing and can also be enzymatically computed to solve simplified 3 × 3 chess and sudoku problems. Our study establishes a feasible route for utilizing the high information density and parallel computational advantages of nucleic acids.

Recyclable Homogeneous Catalysis Enabled by Dynamic Coordination on Rhodium(II) Axial Sites of Metal-Organic Polyhedra.

The activity of catalytic nanoparticles is strongly dependent on their surface chemistry, which controls colloidal stability and substrate diffusion toward catalytic sites. In this work, we studied how the outer surface chemistry of nanostructured Rh(II)-based metal-organic cages or polyhedra (Rh-MOPs) impacts their performance in homogeneous catalysis. Specifically, through post-synthetic coordination of aliphatic imidazole ligands onto the exohedral Rh(II) axial sites of Rh-MOPs, we solubilized a cuboctahedral Rh-MOP in dichloromethane, thereby enabling its use as a homogeneous catalyst. We demonstrated that the presence of the coordinating ligand on the surface of the Rh-MOP does not hinder its catalytic activity in styrene aziridination and cyclopropanation reactions, thanks to the dynamic Rh-imidazole coordination bond. Finally, we used similar ligand exchange post-synthetic reactions to develop a ligand-mediated approach for precipitating the Rh-MOP catalyst, facilitating the recovery and reuse of Rh-MOPs as homogeneous catalysts.

Portable point-of-care surface enhanced Raman scattering spectroscopy for the quantification of glutathione in whole blood microsamples

Glutathione (GSH) is a non-protein tripeptide thiol that plays a prominent role in oxidative stress defense. GSH concentration is particularly critical in the neonatal period, especially for premature newborns that face increased susceptibility to oxidative stress. Monitoring GSH levels provides valuable insights into newborn health, helping to tailor care to their specific needs. The aim of this study was the development of a sensor specifically targeted for its use in neonatology, enabling GSH determination in only 2 μL of whole blood. The newly developed sensing system simplifies sample processing, addressing a critical need in clinical applications. Unlike current methods that demand fast pre-processing of relatively large sample volumes, expensive equipment, and skilled personnel, the developed approach streamlines the analytical process. By using 2 μL of whole blood, a single syringe filter for sample treatment, a deuterated internal standard (IS) for signal normalization, and Surface Enhanced Raman Scattering (SERS) spectroscopy with a silver colloid substrate for GSH detection, the set-up's characteristics are compatible with point-of-care applications. The analytical procedure was validated and applied to diverse populations including healthy adults (N = 63) and newborns (N = 35), yielding GSH concentration values ranging from 0.6 to 1.8 and 0.8–2.1 mM, respectively. This new optical sensor offers a quick and cost-effective solution to support the assessment of GSH levels in newborns that can greatly benefit not only neonatal care, but also the study of adult populations for health monitoring.

Exploring Colloidal Phase Transitions of Imogolite Nanotubes by Evaporation Induced Self‐Assembly in Levitation

AbstractEvaporation‐induced self‐assembly (EISA) is a versatile method for generating organized superstructures from colloidal particles, offering diverse design possibilities through the manipulation of colloid size, shape, substrate nature, and environmental conditions. While some work highlighted the potential of EISA to investigate phase transitions of inorganic liquid crystals, the influence of sample environment to determine their phase diagrams is often overlooked. In this work, the self‐assembly of lyotropic liquid crystals is compared by EISA on substrates, and by acoustic levitation (absence of substrate). The focus is on imogolite nanotubes, a model colloidal system of 1D charged objects, due to their tunable morphology and rich liquid‐crystalline phase behavior. It demonstrates the feasibility to obtain phase transitions in levitating droplets and on soft hydrophobic substrates, whereas self‐assembly is limited on rigid hydrophilic supports. Moreover, the aspect ratio of the nanotubes proves to be a pivotal factor, influencing both transitions and the resulting materials shape and surface. Besides material shaping, acoustic levitation emerges as a promising method for studying phase transitions by EISA, toward the rapid establishment of phase diagrams from diluted to highly concentrated states using a limited volume of sample.

Colloidal carbon soot templated TiO2/Ag surface functionalized 3D printed metal brushes as new generation surface enhanced Raman scattering substrates

This present work demonstrated the functional transformation of 3D printed metal substrates into a new family of Surface-enhanced Raman Scattering substrates, a promising approach in developing SERS-based Point-of-care (PoC) analytical platforms. l-Powder Bed Fusion (l-PBF, Additive manufacturing or 3D printing technique) printed metal substrates have rough surfaces, and exhibit high thermal stability and intrinsic chemical inertness, necessitating a suitable surface functionalization approach. This present work demonstrated a unique multi-stage approach to transform l-PBF printed metal structures as recyclable SERS substrates by colloidal carbon templating, chemical vapor deposition, and electroless plating methods sequentially. The surface of the printed metal structures was functionalized using the colloidal carbon soot particles, that were formed by the eucalyptus oil flame deposition method. These carbon particles were shown to interact with the metals present in the printed structures by forming metal carbides and function as an adlayer on the surface. Subsequent deposition of TiO2 onto these templates led to strong grafting of TiO2 and retaining the fractal structure of the soot template onto the metal surface. Electroless deposition of silver nanoparticles resulted in the formation of fractally structured TiO2/Ag nanostructures and these functionalized printed metal structures were shown as excellent SERS substrates in enhancing the vibrational spectral features of Rhodamine B (RhB). The presence of TiO2 photocatalyst on the surface was shown to remove the RhB analyte from the surface under photochemical conditions, which enables the regeneration of SERS activity, and the substrate can be recycled. The migration of metals from the printed metal structures into the fractally ordered TiO2/Ag nanostructures was found to enhance the photocatalytic activity and increase the recyclability of these substrates. This study demonstrates the potential of 3D-printed Inconel metal substrates as next-generation recyclable SERS platforms, offering a substantial advancement over traditional colloidal, thin-film, flexible, and hard SERS substrates.

Fermented milk product “Narineh” with Lactobacillus acidophilus in sequential and classical therapy for Helicobacter pylori-associated peptic ulcers

Background: In recent years, there has been a growing dissatisfaction with the classical schemes of the eradication of Helicobacter pylori in ulcerative disease among physicians due to frequent failures in eradication therapy, mostly due to antibiotic resistance. It is a known fact that the Lactobacillus acidophilus inhibits the growth of Helicobacter pylori. Objective: Our main goal was to investigate the ability of the fermented milk product "Narineh,” as a functional food, containing Lactobacillus acidophilus to evaluate the efficiency and incidence of adverse effects in addition to the standard triple scheme of eradication therapy with colloidal bismuth substrate. Methods: The patients with peptic ulcer were divided into 2 groups: control (42 patients) received traditional treatment regimens, including 7 days proton pump inhibitor (PPI) + amoxicillin (A) and clarithromycin (C) in the standard doses and subsequent 14 day De-nol (colloidal bismuth subcitrate); experimental (44 patients) received in addition to this standard conventional scheme "Narineh" - 200g, containing 2x109 Lactobacillus acidophilus one time a day starting from the 8-th day for 4 weeks. The results of the eradication in patients were evaluated after 4 -5 weeks, 6 months, and 12 months after completion of treatment using the C13 respiratory urea test (RUT). Repeated endoscopy with histological biopsies was carried out together with RUT in 4-5 weeks after the completion of treatment, and later (6-12 months) for the identification of recurrent ulcer. Results: The treatment with “Narineh” added to the standard regimen significantly reduces the percentage of reinfection and relapse of the disease with a statistical difference (P<0,05). The combination of fermentation milk product “Narineh”, containing Lactobacillus acidophilus with bismuth subcitrate, doesn’t cause a violation of biocenosis of the large intestine, in contrast to the PPI and antibiotics with a statistical difference (P<0,05). In addition, it provides the normalization of gut biocenosis and reduces the frequency of antibiotic-associated diarrhea and other side effects. Conclusion: The treatment with “Narineh” added to the standard scheme is more effective for eradication of Helicobacter pylori infection and significantly reduces the percentage of reinfection and relapse of the disease and lessens the side effects of medications. Keywords: peptic ulcer, eradication Helicobacter pylori, side effects reinfection, fermented milk product “Narineh”, Lactobacillus acidophilus, functional foods

Advancements in mercury detection using surface-enhanced Raman spectroscopy (SERS) and ion-imprinted polymers (IIPs): a review.

Mercury (Hg) contamination remains a major environmental concern primarily due to its presence at trace levels, making monitoring the concentration of Hg challenging. Sensitivity and selectivity are significant challenges in the development of mercury sensors. Surface-enhanced Raman spectroscopy (SERS) and ion-imprinted polymers (IIPs) are two distinct analytical methods developed and employed for mercury detection. In this review, we provide an overview of the key aspects of SERS and IIP methodologies, focusing on the recent advances in sensitivity and selectivity for mercury detection. By examining the critical parameters and challenges commonly encountered in this area of research, as reported in the literature, we present a set of recommendations. These recommendations cover solid and colloidal SERS substrates, appropriate Raman reporter/probe molecules, and customization of IIPs for mercury sensing and removal. Furthermore, we provide a perspective on the potential integration of SERS with IIPs to achieve enhanced sensitivity and selectivity in mercury detection. Our aim is to foster the establishment of a SERS-IIP hybrid method as a robust analytical tool for mercury detection across diverse fields.

Au-Coated ZnO Surface-Enhanced Raman Scattering (SERS) Substrates: Synthesis, Characterization, and Applications in Exosome Detection.

Developing a biomolecular detection method that minimizes photodamage while preserving an environment suitable for biological constituents to maintain their physiological state is expected to drive new diagnostic and mechanistic breakthroughs. In addition, ultra-sensitive diagnostic platforms are needed for rapid and point-of-care technologies for various diseases. Considering this, surface-enhanced Raman scattering (SERS) is proposed as a non-destructive and sensitive approach to address the limitations of fluorescence, electrochemical, and other optical detection techniques. However, to advance the applications of SERS, novel approaches that can enhance the signal of substrate materials are needed to improve reproducibility and costs associated with manufacture and scale-up. Due to their physical properties and synthesis, semiconductor-based nanostructures have gained increasing recognition as SERS substrates; however, low signal enhancements have offset their widespread adoption. To address this limitation and assess the potential for use in biological applications, zinc oxide (ZnO) was coated with different concentrations (0.01-0.1 M) of gold (Au) precursor. When crystal violet (CV) was used as a model target with the synthesized substrates, the highest enhancement was obtained with ZnO coated with 0.05 M Au precursor. This substrate was subsequently applied to differentiate exosomes derived from three cell types to provide insight into their molecular diversity. We anticipate this work will serve as a platform for colloidal hybrid SERS substrates in future bio-sensing applications.

Templated Droplet Evaporation‐Based Supraparticles in Environmental Applications

AbstractDesigning of innovative technologies for the development of functional materials remain crucial for achieving sustainable technological advancements. In this regard, nanoparticles (NPs) possessing enormous potential properties can be obtained using various facile methods for several applications. Adopting NPs as primitive building blocks can initiate the formation of complex entities named supraparticle (SP) to create several advanced functional materials. Additionally, SPs enable entirely new material characteristics to the system, owing to their individual entities, intrinsic properties such as coupling, spatial arrangement, and co‐localization. Indeed, methods such as template‐induced evaporation‐based assembly of NPs direct the shape, size, and morphology of SPs from their respective colloidal dispersions on a solvent‐repellant solid surface. Therefore, it is important to comprehend the formation of SPs and their structure‐property relationship with respect to practical application. This review presents a brief overview of SPs assembly by outlining the templated‐assisted evaporation‐based methodologies for synthesizing SPs. Further, the effect of various factors on the interaction between colloidal entities, solvent, and substrate, leading to the genesis of SPs is elaborated. Conclusively, specific properties are described and applications of SPs for energy storage, generation, and environmental remediation are reported, which collectively brings many interdisciplinary research fields to the same podium.

Novel dipole-enhancement mechanism and detection of high-sensitivity trace environmental hormone bisphenol A with LiCl as co-adsorbates using simple metal-nanoparticle-free solid SERS substrates

Some halogen ions (X = Cl-,Br-,I-) dissociated from alkali-metal-salt analyte (NaX(aq), KX(aq)) were used to enhance SERS signals in colloid substrates. The currently proposed mechanisms of halogen ions enhanced colloid SERS signals is the halogen ions as an aggregating agent to enhance analyte molecules on the hotspots. No effect of solid-state halogen salt on the solid SERS substrates is reported and remaining unclear. Here, a novel dipole-enhancement mechanism of new LiCl(s) salt addition to bisphenol A (BPA) of environmental hormone as co-adsorbates on solid SERS substrates is proposed, which exhibits the strong dipoles interaction of the solid state LiCl(s) with phenol and the better affinity of LiCl-BPA than BPA on the surface of substrate. The dipoles of solid-state LiCl(s) can attract the OH- bonds and benzene rings of BPA molecules, leading to specific amplification of those closer bonds. Also, LiCl interrupts the H-bonds of solution, resulting in better affinity and hydrophilicity, which enables nonspecific amplification of SERS spectra. A low concentration of 1 ppb BPA was detected by adding 1 wt% LiCl and a good coefficient of determination (R2 =0.9955) of BPA was achieved. Testing commercial plastic spoons and zipper bags with Bisphenol about 7.3 and 20.1 ppb were practically demonstrated.

Activated carbon@silver nanoparticles conjugates as SERS substrate for capturing malathion analyte molecules for SERS detection

AbstractMalathion is one of the commonly used organophosphate pesticides known to attack the central nervous system, posing a risk to humans and other animals upon exposure. The surface enhanced Raman spectroscopy (SERS) has been identified as an indispensable tool for chemical and biomolecular sensing. In this work, the facile fabrication of activated carbon (AC)‐based colloidal SERS active substrate dubbed AC@AgNPs was designed by trapping AgNPs on the surface of AC for detection of varying concentrations of malathion. Apart from the higher concentrations of malathion, the rest of the normal Raman spectra of malathion standard solutions exhibited weak Raman signals. The intensity of peaks for 0.47 mg L−1 were nearly non‐existent which is an indication that the malathion pesticide could only be detected up to 0.95 mg L−1 when using silica wafer. On the contrary, all the SERS spectra of malathion in wheat extracts adsorbed on AC@AgNPs substrate exhibited strong Raman signals. Quantitative analysis of malathion was performed by regression models developed using PLSR built with the raw spectra (no pretreatment), SNV‐PLSR, and SNV‐CARS‐PLSR. The model with the most remarkable performance was established by using SNV‐PLSR with r = 0.9869 and RPD = 4.61. This research shows that the proposed method can rapidly detect malathion residues in wheat, suggesting that it could be adopted for production process monitoring of other related food products to guarantee their safety for human and animal consumption.

SERS determination of sodium saccharin content on the tipping paper of cigarettes using AgNP substrates prepared with a USB-power supply device.

A novel magnetic agitating heater powered by a USB port has been developed and applied to synthesize silver colloid substrate for surface-enhanced Raman scattering (SERS) detection of sodium saccharin content on the tipping paper of cigarettes. The heater device allows the convenient synthesis of the Ag colloid, and the reaction can be completed on-site in 15 min under mild conditions. The on-site synthesis of SERS substrate effectively avoided the need for storage and concerns regarding the poor stability and short lifespan of colloid substrates. The results demonstrated that the substrate obtained with the device could achieve SERS detection of Rhodamine 6G (R6G) at as low as 10-9 mol L-1 while maintaining a stable intensity with a relative standard deviation (RSD) of 5.52% (n = 5). Using the prepared substrate at the optimal conditions, the limit of detection of sodium saccharin (SS) was 1 mg L-1. By introducing an internal standard KSCN, a linear relationship was observed between the relative intensity at 708 cm-1 and the concentration of the SS in a range of 20-100 mg L-1 (R2 = 0.98). With the developed method, SS was directly extracted from the cigarette paper by immersing it in water, and the extracted solution was subsequently detected. The quantitative spike-recoveries were in the range of 95.5-116.7%, with RSD between 2.3-12.6%. The whole detection procedure including the on-site substrate preparation, took only about 30 min. This work opens new avenues for colloidal synthesis, and the detection method of SS on the cigarette paper also holds great promise in food safety applications.

Contactless and robust dielectric microspheres-assisted surface-enhanced Raman scattering sensitivity improvement for anthrax biomarker detection.

This report presents a contactless and robust dielectric microspheres (DMs)-assisted surface enhanced Raman scattering (SERS) enhancement method to improve SERS detection sensitivity detection sensitivity. DMs that could focus and collect light were embedded within the polydimethylsiloxane (PDMS) film to avoid direct contact with the analytical solution and improve detection reliability. The as prepared DMs embedded PDMS DMs PD MS film was integrated with a microfluidic technique to enhance the SERS signal of a liquid substrate. Detection in microfluidic systems can reduce reagent consumption, shorten assay time, and avoid evaporation of the colloid substrate solution. The robustness and potential influencing factors of DMs PDMS film assisted SERS enhancement (DERS) were evaluated using 4-aminothiophenol (4-ATP) as the Raman probe. The sensing performance of the proposed method toward dipicolinic acid (DPA) was evaluated, and an evident signal intensification was obtained. Remarkably, the DMs PDMS film can also be implemented on solid substrates. A proof-of-concept experiment was performed by covering the DMs PDMS film directly over an AgNPs@Si solid substrate wherein a 5.7-fold sensitivity improvement was achieved.

Electrostatic layer-by-layer deposition of diamond nanoparticles onto substrate surfaces

Diamond nanoparticles (DNPs) are expected as splendid coating materials to give, e.g. corrosion resistance, anti-bacterial properties, and antireflection function. In this paper, we demonstrate a technique of electrostatic layer-by-layer deposition of DNPs onto substrate surfaces using DNP colloidal suspensions with different signs of zeta potentials alternately. The formed DNP layers are investigated in terms of film thickness, surface roughness, and homogeneity. Plus, those morphologies of DNP layers are theoretically correlated with the colloidal properties of DNP suspensions based on the electrostatic interaction potential energy between colloidal DNPs and substrate surfaces. Consequently, it turns out that the demonstrated technique enables formation of DNP thin layers with desired thickness, particle density, and surface roughness on substrate surfaces by controlling the ionic strength of colloidal DNPs.

Identification, cloning, and characterization of a novel chitinase from leaf-cutting ant Atta sexdens: An enzyme with antifungal and insecticidal activity

Chitinases are enzymes that degrade chitin, a polysaccharide found in the exoskeleton of insects, fungi, yeast, and internal structures of other vertebrates. Although chitinases isolated from bacteria, fungi and plants have been reported to have antifungal or insecticide activities, chitinases from insects with these activities have been seldomly reported. In this study, a leaf-cutting ant Atta sexdens DNA fragment containing 1623 base pairs was amplified and cloned into a vector to express the protein (AsChtII-C4B1) in Pichia pastoris. AsChtII-C4B1, which contains one catalytic domain and one carbohydrate-binding module (CBM), was secreted to the extracellular medium and purified by ammonium sulfate precipitation followed by nickel column chromatography. AsChtII-C4B1 showed maximum activity at pH 5.0 and 55 °C when tested against colloidal chitin substrate and maintained >60% of its maximal activity in different temperatures during 48 h. AsChtII-C4B1 decreased the survival of Spodoptera frugiperda larvae fed with an artificial diet that contained AsChtII-C4B1. Our results have indicated that AsChtII-C4B1 has a higher effect on larva-pupa than larva-larva molts. AsChtII-C4B1 activity targets more specifically the growth of filamentous fungus than yeast. This work describes, for the first time, the obtaining a recombinant chitinase from ants and the characterization of its insecticidal and antifungal activities.

Determination of thiram in tobacco by surface-enhanced differential Raman spectroscopy

This study had developed a rapid, simple, accurate, and efficient method for the qualitative and quantitative determination of thiram residues tobacco and tobacco products based on surface-enhanced Raman spectroscopy and differential Raman spectroscopy. Acetonitrile was used as the extractant and PSA and GCB as the scavengers to effectively reduce the matrix effect. At the same time, sodium chloride and hydrochloric acid were used to induce the agglomeration of the target molecule and the nano particles of enhanced colloid substrates. With this approach to improve the sensitivity of analysis, our results showed that the fine linear equations of thiram with the correlation coefficients equaled 0.9986. The detection of limits was 0.0084 mg/L and the recovery was within 85–117% and the RSD was less than 10%. The detection method of thiram had a good accuracy and precision, which was potentially suitable for other dithoicarbamate pesticide residues in tobacco and tobacco products.

Determination of thiram in tobacco by surface-enhanced differential Raman spectroscopy

This study had developed a rapid, simple, accurate, and efficient method for the qualitative and quantitative determination of thiram residues tobacco and tobacco products based on surface-enhanced Raman spectroscopy and differential Raman spectroscopy. Acetonitrile was used as the extractant and PSA and GCB as the scavengers to effectively reduce the matrix effect. At the same time, sodium chloride and hydrochloric acid were used to induce the agglomeration of the target molecule and the nano particles of enhanced colloid substrates. With this approach to improve the sensitivity of analysis, our results showed that the fine linear equations of thiram with the correlation coefficients equaled 0.9986. The detection of limits was 0.0084 mg/L and the recovery was within 85–117% and the RSD was less than 10%. The detection method of thiram had a good accuracy and precision, which was potentially suitable for other dithoicarbamate pesticide residues in tobacco and tobacco products.

Application of slow-releasing green denaturing colloidal substrates to contain and bioremediate hexavalent-chromium plume

Chromium (Cr) is a major heavy metal pollutant that has been found in many groundwater-polluted sites. The effectiveness of hexavalent chromium [Cr(VI)] plume containment and remediation via the bioreduction and adsorption mechanisms were evaluated in this study using the developed green slow-releasing denaturing-colloidal substrates (G-SDS). The major components of G-SDS were gelatin, agar, and cane molasses (optional), and weight ratios for gelatin and agar were 3 and 0.5%, respectively. Gelatin was used for slow carbon release and Cr(VI) adsorption, cane molasses was applied for rapid carbon release, and agar was used as the solidifying agent to form G-SDS. Environmental scanning electron microscope analyses indicate that the G-SDS had a rigid and stable 3-D structure with irregular and rippled surface and staged sheets, which created significant surface areas for Cr(VI) adsorption. Results from the column study show that more than 98% of Cr(VI) was removed with increased Cr(III) concentrations in column effluents. The G-SDS could form a permeable and reticulated fiber biobarrier after its injection for Cr(VI) adsorption. The released carbon substrate from G-SDS could subsequently enhance Cr(VI) bioreduction mechanisms. The released amine from gelatin could react with water and produce ammonia, which could neutralize the acidified water due to the produced organic acids from G-SDS fermentation. The microbial communities in column soils were characterized by the next-generation sequencing technology. G-SDS supplement caused the variations in microbial diversities and predominant bacteria. The released carbon from G-SDS resulted in the formation of anaerobic conditions , and thus, the growth of the Cr(VI) reducer was enhanced. G-SDS could serve as a source of primary substrate for Cr(VI) bioreduction. The dominant groups of bacterial communities include Acinetobacter, Bacillus sp., Clostridium , Desulfovibrio, and Geobacter . Both G-SDS and column soils contained significant amounts of Cr(III) after the column experiment indicating that the adsorbed Cr(VI) within G-SDS was bioreduced to Cr(III). Moreover, Cr(OH) 3 was formed and precipitated in soils after Cr(VI) bioreduction. Results indicate that the passive biobarrier system containing G-SDS can be used as an economically and practically acceptable remedial system to contain the Cr(VI) plume and reduce the environmental risks caused by Cr(VI). G-SDS can enhance Cr(VI) removal via the development of bioreduction, adsorption, and precipitation mechanisms. • The developed G-SDS can remove Cr(VI) via the bioreduction and adsorption. • G-SDS forms semi-solidified colloid for slow and long-term carbon release. • Cr(OH) 3 is formed and precipitated after Cr(VI) bioreduction. • Dominant CRB include Acinetobacter, Bacillus , Clostridium, Desulfovibrio and Geobacter. • Released amine from G-SDS can produce ammonia, which has the buffering capacity.

SERS detection of anthraquinone dyes: Using solvothermal silver colloid as the substrate

Anthraquinone dyes have been widely used to color textile fibers since antiquity. Identification of the dyes can help us understand the dyeing processes and when and where the textiles were produced. Herein, we present a strategy based on surface-enhanced Raman scattering (SERS) with a novel silver colloid substrate for the detection of anthraquinone dyes. Quasi-spherical silver particles with different sizes were prepared by the solvothermal method and then characterized by transmission electron microscopy (TEM). The silver colloid substrates exhibited high-density hot spots with good reproducibility (RSDs of 3 ∼ 16 %) and high sensitivity. Among them, Ag-C2 (the molar ratio of AgNO3 to PVP is 0.367, reacted for 2 h) was used to detect anthraquinone dyes in reference silk fibers as well as ancient textile samples due to the highest sensitivity and the low RSD (5.37 %) in this study. More importantly, Ag-C2 can be utilized to distinguish three madder species (Rubia tinctorum, Rubia cordifolia, and Rubia argyi) depending on the SERS intensity of alizarin and purpurin.

Bioremediation of hexavalent-chromium contaminated groundwater: Microcosm, column, and microbial diversity studies

Sulfate reducing bacteria (SRB) have the capability of bioreducing hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)] under sulfate-reducing conditions for toxicity reduction. However, a high amount of sulfate addition would cause elevated sulfide production, which could inhibit the growth of SRB and result in reduced Cr(VI) bioreduction efficiency. A slow release reagent, viscous carbon and sulfate-releasing colloidal substrates (VCSRCS), was prepared for a long-lasting carbon and sulfate supplement. In the column study, VCSRCS was injected into the column system to form a VCSRCS biobarrier for Cr(VI) containment and bioreduction. A complete Cr(VI) removal was observed via the adsorption and bioreduction mechanisms in the column with VCSRCS addition. Results from X-ray diffractometer analyses indicate that Cr(OH)3(s) and Cr2O3(s) were detected in precipitates, indicating the occurrence of Cr(VI) reduction followed by Cr(III) precipitation. Results from the Fourier-transform infrared spectroscopy analyses show that cell deposits carried functional groups, which could adsorb Cr. Addition of VCSRCS caused increased populations of total bacteria and dsrA, which also enhanced Cr(VI) reduction. Microbial diversity results indicate that VCSRCS addition resulted in the growth of Cr(VI)-reducing bacteria including Exiguobacterium, Citrobacter, Aerococcus, and SRB. Results of this study will be helpful in developing an effective and green VCSRCS biobarrier for the bioremediation of Cr(VI)-polluted groundwater.