Surface Plasmon Absorption Band Research Articles

Effect of various concentrated copper and plant extract concentrations on the antibacterial activity.

Copper nanoparticles (Cu NPs) were created using two methods, one with reducing and stabilizing agents and the other with green tea extract. The formation of Cu NPs has been described by spectra of UV-Vis absorption, which showed the surface plasmon resonance (SPR) at 620 and 630 nanometers, respectively. The position and shape of the surface plasmon resonance and plasmon absorption bands strongly depend on the reaction conditions. The crystalline morphology and size of the nanoparticles were determined by XRD, FESEM, and TEM studies. In both ways, the average particle size of Cu nanoparticles was found to be in the range of 28 nm and 142 nm for the chemical and green methods, respectively. The effectiveness of the materials prepared by both methods was high, and the antibacterial activity of the products prepared by both ways was against E. coli and S. aureus pathogens represented by inhibition zones ranging from 14–20 mm, 30–38 mm, and 11–18 mm, 20–24 mm, respectively.

Synthesis and Characterization of the Nanogold-Bound Ternary Copper(II) Complex of Phenanthroline and Cysteine as Potential Anticancer Agents.

The aim of this study was to synthesize and characterize a nanogold–{[(Cu)(phen)(cys)(H2O)]NO3}n conjugate and to evaluate its antiproliferative property against the breast cancer cell line (MCF7) and normal cell line (MCF10A). Nanogold solution was prepared using the Turkevich method. In one approach, a ternary copper(II) complex of 1,10-phenanthroline with l-cysteine, [(Cu)(phen)(cys)(H2O)]NO3, was first prepared and then tethered with the gold nanoparticles. In another approach, gold nanoparticles were reacted with l-cysteine, copper(II) nitrate, and 1,10-phenanthroline subsequently. The synthesized [(Cu)(phen)(cys)(H2O)]NO3 complex was characterized by Fourier transform infrared (FTIR) and electrospray ionization mass spectrometry techniques, which showed that l-cysteine was bound to the copper through carboxylic and amino groups, with the thiol moiety remaining free. The free thiol group was bound to the nanogold surface to form the nanogold–{[(Cu)(phen)(cys)(H2O)]NO3}n conjugate, as evidenced by the increase in the surface plasmon absorption band in ultraviolet–visible and the absence of a thiol peak in FTIR of the nanogold–copper complex conjugate. The anticancer activity of the nanogold–copper complex conjugate and the free copper complex against a breast cancer cell line (MCF7) and their toxicity on a normal cell line (MCF10A) were examined using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy phenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. Results suggested that the nanogold–{[(Cu)(phen)(cys)(H2O)]NO3}n conjugate demonstrates a selective antiproliferative and proapoptotic effect on the breast cancer cells, confirming the potential of the nanogold–copper complex conjugate as an anticancer agent.

Electrochemistry as a Complementary Technique for Revealing the Influence of Reducing Agent Concentration on AgNPs.

The synthesis process of AgNPs has been attracting a lot of attention in the fields of biosensors/sensors, diagnostics, and therapeutic applications. An attempt to understand the effect of different concentrations of reducing agents on the synthetic design process has been made. In this paper, we gather information on voltammetry studies and relate it with UV–vis and scanning electron microscopy (SEM) analyses. Given the kinetics, localized surface plasmon absorption (LSPR) band, and narrow size distribution of these methods, it was possible to compare the obtained measurements and clearly distinguish sizes and aggregation. AgNPs measured by SEM showed a statistically significant reduction of the nanoparticle sizes from 65 to 37.5 nm as the reducing agent increased. Well-matched d-spacing data calculated from selected area electron diffraction (SAED) patterns and X-ray diffraction (XRD) were obtained for all of the samples. The UV–vis studies showed that the SPR bands shift toward the blue region as the reducing agent concentration is increased, indicating a decrease in particle sizes. It is worth emphasizing that cyclic voltammetry (CV) and differential pulse voltammetry (DPV) coincide well with SEM on the aggregation of AgNPs at higher concentrations. A 10 mM reducing agent concentration resulted in uniform outcomes for producing AgNPs with the smallest size in terms of full width at half-maximum (FWHM) in all of the methods used in this study, while UV–vis band gaps increase with increasing reducing agent concentration. In agreement with all of the methods investigated, the results suggested that the best concentration of the reducing agents is 10 mM for a target application. These findings suggest the usefulness of voltammetry as a complementary method that can be used as a qualitative guide to identify the size and aggregation of NPs.

Plasmon Resonant Two-Photon Luminescence Inducing Photosensitization and Nonlinear Optical Microscopy In Vivo by Near-Infrared Excitation of Au Nanopeanuts

Photodynamic therapy (PDT) provides a potential therapeutic approach for killing malignant cell/solid tumors, but currently approved photosensitizers (PSs) are generally excited by visible light, limiting the penetration depth in tissues. It is necessary to develop a near-infrared (NIR) responsive photodynamic platform, providing maximum tissue penetration. Here, we present a gold nanopeanut platform exhibiting dual functions of NIR PDT and two-photon luminescence imaging. The nanopeanut with a size less than 100 nm exhibits two distinct NIR surface plasmon absorption bands at approximately 1110 and 1300 nm. To perform PDT, we conjugated commercial toluidine blue O (TBO) PS on the surface of the nanopeanuts. With spectral overlap, the 1230-nm femtosecond Cr: forsterite laser can excite the surface plasmons of nanopeanuts, transfer energy to TBO, and generate singlet oxygen to kill cells. Moreover, the plasmon resonance-enhanced two-photon luminescence of nanopeanuts can be used to map their delivery in vivo. These results demonstrate that the PS-conjugated gold nanopeanut is an effective theranostic system for NIR PDT.

Silver Nanoparticle-Based Sensor for the Selective Detection of Nickel Ions.

Silver nanoparticles (AgNPs) can be used as a surface plasmon resonance (SPR) colorimetric sensor; the correlation between the SPR phenomenon and the aggregation state of nanoparticle allows the real-time detection of a target molecule. Surface functionalization of NPs with proper molecular baits is often performed to establish the selectivity of the sensor. This work reports on the synthesis of AgNPs under reducing conditions and on the functionalization thereof with mercaptoundecanoic acid (11-MUA). UV-VIS Spectroscopy confirmed the formation of AgNPs, eliciting a surface plasmon absorption band (SPAB) at 393 nm that shifted to 417 nm upon surface coating. Dynamic light scattering was used to investigate the surface coatings; moreover, pelleted AgNPs@11MUA nanoparticles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analyzers (EDX), and infrared spectroscopy to corroborate the presence of 11MUA on the surface. Most interestingly, the resulting AgNPs@11MUA selectively detected micromolar levels of Ni2+, also in the presence of other cations such as Mn2+, Co2+, Cd2+, Cu2+, Zn2+, Fe2+, Hg2+, Pb2+, and Cr3+.

A Gold Nanoparticle-Based Colorimetric Probe for Detection of Gibberellic Acid Exuded by Ralstonia solanacearum Pathogen in Tomato (Solanum lycopersicum L.)

We reported a simple colorimetric probe based on gold nanoparticles (AuNPs) for detecting Ralstonia solanacearum. The AuNPs were synthesized through reduction with citrate ion and characterized by ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The freshly synthesized AuNPs were brick red due to an intense surface plasmon absorption band at 520 nm. Upon interaction with synthetic gibberellic acid (GA3), a bathochromic shift occurred in the surface plasmon resonance (SPR) peak of AuNPs to higher wavelengths. The 'eye-ball' limit of detection was 0.2 ppm. This shift was accompanied by a change in the color of the AuNPs from brick red to purple. Soil samples were collected from the rhizosphere of tomato plants, exhibiting bacterial wilt symptoms and pure cultures of Ralstonia solanacearum isolated using a modified Kelman’s TZC medium. Gibberellins (GA) were extracted from the culture of R. solanacearum using ethyl acetate and characterized using fourier transform infrared spectroscopy (FT-IR). AuNP solution aggregation was induced by GA-mediated R. solanacearum. A color change from brick red to purple was also observed. The results illustrated the use of both SPR wavelength-shift sensing and visual color change to detect molecules of biological relevance.

Nanoporous gold nanoleaf as tunable metamaterial

We have studied optical properties of single-layer and multi-fold nanoporous gold leaf (NPGL) metamaterials and observed highly unusual transmission spectra composed of two well-resolved peaks. We explain this phenomenon in terms of a surface plasmon absorption band positioned on the top of a broader transmission band, the latter being characteristic of both homogeneous “solid” and inhomogeneous “diluted” Au films. The transmission spectra of NPGL metamaterials were shown to be controlled by external dielectric environments, e.g. water and applied voltage in an electrochemical cell. This paves the road to numerous functionalities of the studied tunable and active metamaterials, including control of spontaneous emission, energy transfer and many others.

Charge Transfer in 4-Mercaptobenzoic Acid-Stabilized Au Nanorod@Cu2O Nanostructures: Implications for Photocatalysis and Photoelectric Devices

Nanoscale materials have an irreplaceable advantage in solar energy utilization because of their perfect match with visible light wavelength on the length scale. Charge transfer (CT) between a metal nanoparticle and contacted nanoscale semiconductor plays a significant role in photoinduced energy transfer. Here, we fabricated a new complex, a gold nanorod-4-mercaptobenzoic acid@Cu2O (Au NR-MBA@Cu2O) core–shell nanostructure, and used surface-enhanced Raman scattering (SERS) spectroscopy of the interlayer MBA molecules to investigate the CT process occurring between the Au NRs and Cu2O. In our system, different surface plasmon absorption bands were adjusted by tuning the thicknesses of the Cu2O shells on the Au NR core to explore the influence of plasmon absorption at different incident Raman laser lines. By analyzing the SERS spectra, the degree of CT was calculated, and the consequences can be fully explained by photoexcitation across interface electron transfer and plasmon-induced interfacial charge transfer transition at laser excitation wavelengths of 633 and 785 nm. This experiment introduced a simple, effective, and intuitive approach to observe the CT process in metal semiconductors by SERS. The results of our study will improve in photocatalytic efficiency and photoelectric devices.

Colorimetric Sensor Based on β-Cyclodextrin-Functionalized Silver Nanoparticles for Zidovudine Sensitive Determination.

Zidovudine (ZDV) is an antiviral drug against HIV that was approved by the FDA on March, 1987. It is a reverse transcriptase inhibitor. This type of drug stops the reproduction of DNA and decreases the amount of the virus in the patients' blood. Due to the ability of forming various molecular bonds, silver nanoparticles (AgNPs) are widely used for the detection of large range of agents, including drugs. In this study, we synthesized AgNP-modified β-cyclodextrin (β-CD) using green synthesis for the sensitive and selective zidovudine (ZDV) determination. Characterization of nanoparticles was done using different methods including infrared (IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), and also, X-ray diffraction (XRD) patterns. The AgNP λ-max peak was at approximately 405 nm. In the presence of ZDV, yellow solution was turned to red color, and surface plasmon absorption band was dramatically centered at 560 nm. ZDV was determined in the range of 50–500 μM, and the detection limit value was obtained as 42 μM. The sensor was used to determine ZDV in tablets with good recovery.

One-step nitrogen plasma process for bimetallic impregnation to obtain N-TiO2−X/Au/Ag composite

The main motivation of this work is to deposit two different metals (gold and silver) on titanium oxide nanoparticles surface in a one-step simple and fast physical process by applying a nitrogen plasma as the main source of nitrogen atoms to obtain nanostructured N-TiO2 − X/Au/Ag materials. The obtained nanomaterials were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. Based on the characterization results, we found that gold and silver nanoparticles were uniformly loaded on the titanium oxide nanocomposite surface, showing a surface plasmon absorption band due to the loading of the metal nanoparticles over titania samples. The results of this work have shown that nitrogen plasma technique is a more feasible and simple alternative to obtain the N-TiO2 − X/Au/Ag nanocomposite. Moreover, this plasma technique could be used to impregnate with other kind of metals over the surface of diverse nanomaterials.

Insight into the Interaction between Selected Antitumor Gold(III) Complexes and Citrate Stabilized Gold Nanoparticles

This paper presents the study of the interaction between gold nanoparticles (AuNPs) and antitumor gold complexes, [Au(OH)2(bipy)][PF6], [Au(CH3COO)2(pydmb-H)], and [Au(bipydmb-H)(OH)][PF6], in order to estimate the possibility for metal complex tracking in cells using nanospectroscopy approach. Decrease of intensity of the surface plasmon absorption band at 524 nm and the appearance of a new broad band at ∼640 nm, followed by their red shift were observed in the presence of the complexes. TEM images showed that the average size and shape of AuNPs did not change after the addition of gold complexes. DLS and zeta potential measurements pointed out to the metal complex adsorption on the surface of AuNPs followed by flocculation process. In addition, kinetic studies indicated strong bond formation between these complexes and AuNPs. Accordingly, AuNPs/complex conjugates have the potential to be applied for the tracking of these metal complexes in the cells using nanospectroscopy approach.

Electrical Energy Storage Capability of Flake-Like/Spherical Structured CuO–Ag Nanocomposite Synthesized by Green Plasmonic Approach

Nanotechnology now offers great ability for storage of electrical energy. The energy storage capability of copper oxide/silver (CuO–Ag) nanocomposite has been investigated using supercapacitor studies. The observation of a peak at 309 nm confirmed the surface plasmon absorption bands in the ultraviolet region. The functional molecules present in the prepared sample were clearly classified by Fourier-transform infrared studies. The crystalline structure of the fabricated nanomaterials followed the monoclinic system. Field-emission scanning electron microscopy evidenced CuO nanomaterial with flake-like structure (∼ 380 nm in size) and Ag nanomaterial with spherical structure (∼ 200 nm in size). Energy-dispersive spectroscopy studies confirmed the purity of the sample by the absence of impurities. The CuO–Ag nanocomposite synthesized using a green method provided remarkable specific capacitance (594 F/g) and stable efficiency during continuous cycles. Electrochemical impedance studies revealed a remarkable improvement in the conductivity (Ret for CuO = 738 Ω, Ret for CuO–Ag = 721 Ω) of the prepared materials.

Helminthicidal and Larvicidal Potentials of Biogenic Silver Nanoparticles Synthesized from Medicinal Plant Momordica charantia.

The drug formulations used to control mosquito vectors and helminth infections have resulted in the development of resistance, and negative impact on non-target organisms and environment. Plant-mediated synthesis of silver nanoparticles (P-AgNPs) using aqueous fruit peel extract of M. charantia, applications of P-AgNPs for helminthicidal activity against Indian earthworms (P. posthuma) and larvicidal activity against larvae of mosquito A. albopictus and A. aegypti. Aqueous fruit peel extract of Momordica charantia was used to reduce silver ions to silver nanoparticles (P-AgNPs). UV-Visible (UV-Vis) Spectroscopy, X-ray diffraction, Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy characterize synthesized P-AgNPs. The motility and survival rate of the worms were recorded for the helminthicidal activity. Percent mortality of larvae of A. albopictus and A. aegypti was recorded for larvicidal activity. The UV-Vis absorption spectrum of P-AgNPs showed a strong surface plasmon absorption band in the visible region with a maximum absorption at 445 nm indicating the synthesis of silver nanoparticles by the addition of aqueous fruit peel extract. The XRD spectrum of P-AgNPs showed Bragg's reflection peaks 2θ value characteristics for the Face-Centered Cubic (FCC) structure of silver. The sharp absorption peak in FTIR at 1659 cm-1 assigned to C=O stretching vibration in carbonyl compounds represents terpenoids, flavonoids and polyphenols in the corona of PAgNPs; a 2 mg/mL of P-AgNPs. The concentration aqueous extract and P-AgNPs showed complete death of worms (the morphological alteration/coiling of body). A 20 ppm concentration of PAgNPs showed 85% mortality in larvae of Ae. albopictus and Ae. aegypti. P-AgNPs were nontoxic at low concentrations. The aqueous extracts played a dual role as reducing and capping agent during the biosynthesis of AgNPs as per FTIR and XRD results. The surface reactivity facilitated by biomolecule corona attached to silver nanoparticles can further help to functionalize AgNPs in various pharmaceuticals, biomedicals, and environmental applications.

Simple and rapid colorimetric sensing of Ni(II) ions in tap water based on aggregation of citrate-stabilized silver nanoparticles

The presence of nickel in our water sources presents a danger to human health and aquatic organisms alike. Therefore, there is a need to detect and monitor nickel concentration in these sources. Current detection methods use instruments that are costly, resource intensive and require skilled personnel. Alternative methods that are simple and fast are needed. This study reports for the first time the development of a simple colorimetric assay for the detection of Ni2+ in aqueous solution using citrate-stabilized silver nanoparticles. Chemical synthesis method was employed using sodium borohydride and trisodium citrate as reducing and stabilizing agents, respectively. The characterization techniques used for obtaining spectral and morphological properties were ultraviolet-visible spectroscopy and transmission electron microscopy. The resultant silver nanoparticle solution was yellow in color and exhibited an absorbance peak at 392 nm. The full width at half maximum value was 57.8 ± 1.3 nm indicating particle monodispersity. For the morphology, the nanoparticles were spherical in shape with an average size of 10.4 ± 4.5 nm. Furthermore, the colorimetric properties of the silver nanoparticles for Ni2+ detection was investigated. Ni2+ was visually detected through a fast solution color change from yellow to orange. Monitoring of the absorbance showed a decrease in the original 392 nm peak and broadening of the surface plasmon absorption band. These changes are attributed to the aggregation of the nanoparticles due to Ni2+ addition which was confirmed by the transmission electron microscopy imaging. The absorption ratio (A510/A392) was plotted against varying Ni2+ concentration and it exhibited a good linear correlation from 0.7 to 1.6 mM with an R2 of 0.9958. The limits of detection and quantification were 0.75 and 1.52 mM, respectively. Additionally, the assay was tested against other common ions and showed excellent selectivity for Ni2+. Finally, the assay was successfully tested to detect Ni2+ in tap water samples with an average difference of 16% from prepared concentrations. Overall, the study showed the potential of using citrate-stabilized silver nanoparticles as a colorimetric reagent for detecting Ni2+ in aqueous solution.

Isaria fumosorosea-based zero-valent iron nanoparticles affect the growth and survival of sweet potato whitefly, Bemisia tabaci (Gennadius).

Nanoparticles can be used for effective pest management as a combined formulation of metal and some other material that has proven efficacy against a given pest. This study reports the synthesis, characterization and efficacy of Isaria fumosorosea-based zero-valent iron (ZVI) nanoparticles against sweet potato whitefly Bemisia tabaci (Gennadius). The I. fumosorosea-ZVI nanoparticles showed a characteristic surface plasmon absorption band at 470 nm during UV-visible spectroscopy. The scanning electron micrographs of nanoparticles showed spherical shaped nanoparticles with sizes ranging between 1.71 and 3.0µm. The EDX analysis showed the characteristic peak of iron at 0.6 and 6.8KeV. The XRD analysis showed characteristic peaks at 44.72°, 65.070°, 82.339° and 82.65°. The bioassay results indicated that the percentage of larval mortality of B. tabaci challenged with I. fumosorosea ZVI nanoparticles was both concentration and age dependent. Isaria fumosorosea ZVI nanoparticles showed high pathogenicity against second and third instar nymphs, and pupae with LC50 values of 19.17, 26.10 and 37.71 ppm, respectively. The LT50 was lowest for second instar nymphs (3.15 days) and highest for pupae (4.22 days) when inoculated with a concentration of 50 ppm. Isaria fumosorosea ZVI nanoparticles can be an eco-friendly tool for effective B. tabaci management. © 2019 Society of Chemical Industry.

Effect of surface Ag metallization on the photocatalytic properties of BaTiO3: Surface plasmon effect and variation in the Schottky barrier height

Surface Ag metallized BaTiO3 samples were prepared by varying Ag concentration in the range of 0.2% to 0.8% by photoreduction method and the performance of these catalysts were tested for the degradation of Rhodamine B dye under the illumination of UV/solar light. The values of lattice parameter, cell volume and lattice strain has increased with increase in the Ag concentration, while the crystallite size decreased with increase in the deposited Ag concentration. The surface plasmon absorption bands of Ag deposited BTO samples showed a red-shift and the absorption bands broadened with increase in the Ag content. The presence of surface metallic silver in the Ag0 state was confirmed by the XPS analysis. The enhanced activity of Ag deposited photocatalyst under UV light is majorly due to the formation of Schottky barrier, creation of metal induced gap states, polarization effects, reduced crystallite size and increased surface area of the photocatalyst. Under solar light it is due to synergistic effects between Surface Plasmon Resonance (SPR) effect and formation of Schottky barriers. The photocurrent measurements substantiates the effective charge transfer migrations. The energy states/term symbols of the metallic Ag under the illumination of UV light is 2S1/2 and it is 2P1/2 under the illumination of solar light.

Anti inflammatory activity of Silver nanoparticles synthesised using Cumin oil

Aim: To evaluate the anti inflammatory activity of silver nanoparticles synthesised using Cumin oil. Introduction: Silver nanoparticles are today a standout amongst the most generally utilised Nanoparticles both in key therapeutic sciences and clinical practice. Silver particles are connected to modified cell demise, and expanded cytotoxicity in specific conditions. Materials and method: Preparation of denaturation particles using Cumin oil and evaluating the anti inflammatory activity by using albumin denaturation assay technique. Results: The characteristic surface plasmon absorption band were observed at 440nm. It is observed that with the increase in concentration, the anti-inflammatory activity of silver nanoparticles increases. Conclusion: Silver nanoparticles synthesized using cumin oil exhibit potent anti inflammatory activity and hence can be used along with anti inflammatory drugs, which would potentiate the effect of the drugs.

Effects of Rare-Gas Matrices on the Optical Response of Silver Nanoclusters

The optical response of silver clusters, Agn with n = 8, 20, 35, 58, and 92, embedded in a rare-gas matrix are calculated in the framework of the time-dependent density functional theory (TDDFT). We present a methodology able to reproduce with unprecedented accuracy the experimental spectra measured on metal clusters embedded in neon, argon, krypton, and xenon solid matrices. In our approach, the metal cluster is surrounded by explicit rare-gas atoms and embedded in a polarizable continuum medium. Interactions with the surrounding medium affect both the position and the width of the surface plasmon absorption band of metal clusters. The size-dependent shift of the surface plasmon band is evaluated in the case of a neon matrix. While the band shifts to lower energies (red shift) for large clusters, it shifts to higher energies (blue shift) for very small clusters.

Gold nanoparticles crosslinking by peptides and amino acids: A tool for the colorimetric identification of amino acids.

Gold nanoparticles are known to aggregate in the presence of proper multifunctional compounds. For those larger than 3 nm, the process can be followed with the naked eye because the surface plasmon absorption band of the particles shifts to longer wavelengths and the solution color changes from red to blue. To exploit this property, we have used amino acids and peptides as crosslinking agents in ethanol at low µM concentrations. In the case of amino acids, we report a straightforward protocol for their colorimetric identification. We also report that the presence of precise secondary structure and conformational constraints in oligopeptides, directly influence their crosslinking ability. A discussion on the nature of the interactions that induce these phenomena is also reported.

Naked Eye Detection of Cr3+ and Ni2+ Ions by Gold Nanoparticles Modified with Ribavirin

This paper reports the synthesis of ribavirin-modified gold nanoparticles (ribavirin-AuNPs) in aqueous media, characterized by FTIR spectroscopy, ultraviolet–visible spectroscopy (UV–vis), and transmission electron microscopy (TEM). Ribavirin-AuNPs were employed as colorimetric probes to detect Cr3+ and Ni2+ in the pH range of 3–8 and 25 ∘C in aqueous solutions by the color change of the system. In the solution, ribavirin-AuNPs were red in color and the surface plasmon absorption band was centered at 530 nm. In the presence of Cr3+ and Ni2+, ribavirin-AuNPs induced the aggregation of nanoparticles, and the surface plasmon absorption changed to 540 nm. Upon aggregation, the surface plasmon absorption band red-shifted and, thus, the nanoparticle solution appeared blue. The sensitivity of ribavirin-AuNPs toward other metal ions, i.e. Mg2+, Mn2+, Cr6+, Na+, Ni2+, Ag+, Al3+, Ca2+, Cd2+, K+, Cd2+, Cu2+, Fe2+, Fe3+, Hg2+, Co3+, Ni2+, Pb2+, and Zn2+, was negligible. This highly selective sensor allowed for the direct quantitative assay of Ni2+ and Cr3+. The limits of detections were found to be 25.2 and 30.5 nM for Ni2+ and Cr3+ on the basis of the signal-to-noise ratio of 3:1 and correlation coefficients (R2) of 0.9813 and 0.99489 for Ni2+ and Cr3+, respectively.