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Semiconductor nanocrystals (NCs), particularly cadmium selenide (CdSe) quantum dots (QDs), are nanoscale particles that exhibit unique size-dependent optical and electronic properties, which make them valuable for applications in optoelectronics, bioimaging, and catalysis. The stabilization and synthesis of QDs are critically influenced by surfactants, which control the size, shape, and surface properties of the QDs. In this study, we investigated the effects of benzoic acid (BA), benzoate (BZ), and eight para-substituted derivatives on the properties of CdSe nanoclusters using density functional theory (DFT). The binding energies and electronic properties of the surfactant-nanocluster complexes were analyzed, demonstrating significant variations based on the nature of the substituent. Electron-donating groups (EDGs) generally enhance binding strength and electronic properties more effectively than electron-withdrawing groups (EWGs). Notably, benzoate derivatives exhibited stronger binding and more substantial modifications to the electronic properties of CdSe nanoclusters than benzoic acid derivatives. These computational insights provide a detailed understanding of the binding interactions, potentially guiding the rational design of surfactants for specific nanocrystal applications. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) have attracted significant interest because of their tunable bandgaps, which enable numerous applications in fields such as photovoltaics, biomedicine, and materials science. This study explores various core electron treatments in the density functional theory (DFT) analysis of II-VI semiconductor quantum dots and their bulk counterparts. We compared All-electron (AE), Effective Core Potential (ECP), All-Electron Relativistic (AER), and DFT-Semicore pseudopotential (DSPP) treatments. Our findings indicate that the AE treatment aligns closely with the experimental results for smaller QDs, whereas the accuracy of DSPP increases with larger QDs. DSPP provides an optimal balance between computational efficiency and accuracy, making it suitable for studying II-VI QDs. Notably, the bandgap behavior varies, being direct for zinc and cadmium chalcogenides, whereas mercury chalcogenides are zero-gap semiconductors (semimetals). The inner bonds of the QDs exhibit an ionic character, whereas the terminal bonds display a covalent character. This study enhances our understanding of the structural and electronic properties of II-VI quantum QDs, aiding their application in various technologies. [ABSTRACT FROM AUTHOR]

The structural, electronic, and quantum confinement effects observed in II–VI quantum dots have been described using density functional theory. Various properties like binding energy, Fermi energy, charge distribution, and band gap of various clusters have been determined as a function of cluster size in order to find out the most stable of all the clusters considered. The binding energies are found to be a function of the cluster size but converge to a maximum. Cadmium is observed to possess a larger tendency to form clusters with higher coordination numbers compared to zinc and mercury. In mercury sulfide (HgS)n, the clusters with n = 6 and 13 get dissociated into two graphene-like parallel layers. The adsorptions of single gas molecules on the (CdSe)13 quantum dots are exothermic, indicating that most of the gas molecules adsorb spontaneously on the CdSe quantum dots. Among the various gases, O2 and NO2 are the gas molecules that get most strongly chemisorbed. The CdSe quantum dot acts as an electron donor when it interacts with the oxidizing gases, O2, CO, NO2, and SO2 gases. The vibrational analysis of the combined systems indicates that the intensities of the peaks due to CdSe reduce after adsorption. Extra peaks appear at higher frequencies due to the adsorbed gas molecules. The present work shows insights into the gas sensing properties of the quantum dots under study. [ABSTRACT FROM AUTHOR]

The growing use of pesticides is a cause of major concern because it poses harm not only to the environment but to human health as well. Chloropicrin (PS) is a volatile organic compound (VOC) used as a fumigant and is hence harmful to the atmosphere and needs to be removed before it can cause any harm. Graphene-based materials have been widely used as decontaminants because of their unique structure and properties. Here we have explored the interaction of not only pristine graphene (PG) but also some of its modified forms using periodic density functional (DF) calculations with dispersion corrections (DFT-D). Several possible modes of adsorption have been explored in each case. The pesticide is only physisorbed on pristine graphene. Doping with boron leads to a further decrease in the adsorption energy, but doping with nitrogen has the opposite effect, leading to a substantial increase in the adsorption energy, but it is still physisorption with no formation of bonds. Doping with BN also leads to negligible adsorption energy. Doping with a stronger n-type dopant, Fe, was also considered, and in this case, there is chemisorption, one C-Cl bond dissociating and the Cl getting attached to the Fe atom. Finally, decoration with a small Fe4 cluster led to the strongest chemisorption, the pesticide getting completely dissociated. We also considered the effect of decreasing number of halogen atoms and change in the halogen on the adsorption on Fe4-decorated graphene. [ABSTRACT FROM AUTHOR]

The various tautomers and conformers of SLC-0111, a well-known biologically potent compound, have been investigated using density functional theory (DFT) calculations in the gas phase and aqueous solution. The amide form is found to be the only stable tautomeric form in both the phases, with the trans-cis conformer as the most stable structure in the gas phase and the trans-trans conformer in aqueous solution. The deprotonation of the sulfonamide nitrogen leading to the formation of the SLC-0111 anion occurs at pH > 10. The various intramolecular interactions and reactivity of the molecule have been characterized using natural bond orbital (NBO) analysis and calculation of global reactivity parameters. The effect of the solvent polarity on the energies and nature of the frontier molecular orbitals has been investigated for both the neutral and anionic forms. Further, the electronic spectra and vibrational spectra of both the states have also been computed and the effect of changing solvents on the electronic spectra has been investigated. The calculated nonlinear optical (NLO) properties of the molecule show that the molecule has potential to be featured as an NLO material. [ABSTRACT FROM AUTHOR]

In the present work, the adsorption of carbaryl (CBL) on the modified graphene substrates has been studied by density functional theory (DFT) for the purpose of water remediation. Carbaryl is a carbamate pesticide used worldwide and has been reported as a potential carcinogen. It has been found that CBL adsorption on pristine graphene is endothermic and highly unfavorable. Further results show that the introduction of vacancy defects and Pt clusters significantly improves the reactivity of the graphene substrates towards the carbaryl molecule. The electron density difference plots give overview of the adsorption behavior of CBL and partial density of states (PDOS) give insights into the magnetic character exhibited by substrates after decorating with the cluster. This study reveals the suitability of Pt-decorated graphene substrates as adsorbents for the removal of CBL pesticide. [ABSTRACT FROM AUTHOR]

Echinatin (Ech), a characteristic retrochalcone isolated from liquorice, a widely used herbal medicine, has been investigated in detail in terms of its conformational and electronic properties in different dielectric media using density functional calculations. Natural bond orbital (NBO) analysis suggests an extended conjugation in the molecule, including a keto-ethylenic group (–CO–CH=CH–) connecting both the rings. The aromaticity of Ech has been studied using the nucleus-independent chemical shift (NICS) method. The acidity constants (pKa) have been simulated for both the hydroxyl groups in the molecule. Molecular electrostatic potentials (MEPs) have been computed to predict the reactivity of Ech toward both electrophiles and nucleophiles. Further, the electronic spectra of the neutral and deprotonated states have been computed in different solvents using an implicit solvation model, SMD. The vibrational spectra of both the neutral and anionic forms have also been simulated. Besides these, 1H-NMR and 13C-NMR spectra have been computed and compared with the experimental values. In addition, the frontier molecular orbital (FMO) energies, a number of global reactivity descriptors, viz., chemical hardness (η), chemical potential (μ), global softness (S), global electrophilicity (ω), and nucleophilicity (N) indices and various thermodynamic parameters have also been calculated in order to get a better insight into the molecular properties. [ABSTRACT FROM AUTHOR]

Adsorption of a toxic gas, methyl isocyanate (MIC), has been studied on different metal (Fe, Ni, and Cu) cluster-decorated graphene and vacancy graphene. The binding of M4 clusters on vacancy graphene surfaces is higher than on pristine graphene. The magnetic properties of all surfaces have also been studied. MIC is weakly adsorbed on graphene and vacancy graphene, but chemisorbed when graphene surfaces are decorated with metal clusters, with high adsorption energy and large Hirshfeld charge transfer. To further investigate the adsorption, electron density difference, density of states (DOS), and partial density of states (PDOS) before and after adsorption were plotted. The band gap of all the surfaces before and after adsorption of methyl isocyanate has also been calculated. [ABSTRACT FROM AUTHOR]

4-Thiazolidinone compounds have been reported to display good antioxidant activity. In the present work, the five-membered ring has been studied extensively at the DFT-B3LYP/6-311(++)G(d,p) level of theory. The geometrical features of the ring have been explored in the gas and solvent phase. Various molecular descriptor characteristics of the antioxidant compound have been calculated and compared with the reference antioxidant, trolox. Three probable antioxidant mechanisms, hydrogen atom transfer (HAT), single electron transfer (SET), and sequential proton loss electron transfer (SPLET), have been explored, both in the gas and solvent phase. It has been found that the ring exerts its antioxidant activity predominantly following the HAT pathway, both in the gas and solvent phase. In order to determine the feasibility of the overall redox reaction, the standard redox potentials have been calculated for the ring and free radicals. Furthermore, the effect of substitution on the antioxidant parameters of the ring has been explored. Results indicate that substitution at the C2 position is advantageous over that at C5 in improving such parameters. Along with this, the effect of substitution at the C2 position on the proton affinity of the C5 position has also been investigated in detail. [ABSTRACT FROM AUTHOR]

Mesoporous magnesium oxide–graphene oxide composite (MGC) has been synthesized using a facile post-immobilization method by mixing pre-synthesized magnesium oxide (MgO) with graphene oxide (GO). MgO used for fabrication of the composite has been synthesized using an environment-friendly method involving gelatin as a template. XRD, Raman and EDX analyses have confirmed the presence of MgO and GO in the composite. FTIR and SEM analyses of synthesized MGC have further elucidated the surface functionalities and morphology, respectively. Using N2 adsorption–desorption isotherm, BET surface area of MGC has been calculated to be 55.9 m2 g−1 and BJH analysis confirmed the mesoporous nature of MGC. The application of synthesized MGC as a selective adsorbent for various toxic anionic dyes has been explored. Batch adsorption studies have been carried out to investigate the influence of different adsorption parameters on the adsorption of two anionic dyes: indigo carmine (IC) and orange G (OG). The maximum adsorption capacities exhibited by MGC for IC and OG are 252.4 and 24.5 mg g−1, respectively. Plausible mechanism of dye adsorption has been explained in detail using FTIR analysis. In a mixture of cationic and anionic dyes, MGC selectively adsorbs anionic dyes with high separation factors, while in binary mixtures of anionic dyes, both dyes are adsorbed efficiently. Thus, MGC has been shown to be a potential adsorbent for the selective removal of anionic dyes from wastewater. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) studies have been performed on the unprecedented adsorption of glyphosate pesticide on modified pyridine-like nitrogen-doped graphene (PNG) for the purpose of water remediation. The interaction of glyphosate on the PNG sheet, as well as on Pt-Cu decorated PNG substrates, is investigated. The Pt4-nCun (n = 0–4) clusters, such as Pt4, Pt3Cu1, Pt2Cu2, Pt1Cu3, and Cu4, have been decorated on the PNG surface to increase the reactivity of the adsorbent toward glyphosate. The adsorption of glyphosate on the PNG surface is physisorption, indicated by the low adsorption energy and negligible charge transfer. The mixed metal (Pt-Cu) clusters play a significant role in enhancing the interactions between the adsorbate and adsorbent, leading to better results for the adsorption of glyphosate. Exothermic chemisorption is shown by all Pt4-nCun clusters decorated PNG substrates, and chemical bond formation takes place between the adsorbate and adsorbent. Various electronic properties, like electron density difference plots, give information about the adsorption behavior of glyphosate, and density of states (DOS) plots reveal that on decorating with the cluster, the substrates start exhibiting magnetic character. [ABSTRACT FROM AUTHOR]

Certain DNA minor groove binders, especially bis-benzimdazole containing compounds, such as Hoechst 33258 and its derivatives, act as potent topoisomerase I inhibitors. The mechanism of action of these drugs is complex and involves hindering the breakage/reunion reaction of topoisomerase I. In the present work, molecular modeling studies have been performed to develop a pharmacophore and 3D-quantitative structure–activity relationship (QSAR) model based on bis- and ter-benzimidazoles, in an attempt to recognize the features that must be present in a molecule for it to behave as a topoisomerase I inhibitor. A data set comprising thirty bis-benzimidazoles and ter-benzimidazoles, known for their cytotoxicity against the RPMI-8402 lymphoblastoma cell line, has been chosen for this study. A five-point common pharmacophore hypothesis (CPH), with two acceptors, one donor and two aromatic features, has been derived for pharmacophore-based alignment of the molecules. The QSAR model, hence generated, shows a reasonable predictive Q2 value of 0.465. The CPH and contour map analyses display features that render antiproliferative properties to molecules against tumor cell lines, thereby ceasing cell growth. Further, the pharmacophore model has been utilized to develop lead molecules that can provide stability to the DNA–topoisomerase I cleavable complex, in turn inhibiting the activity of the enzyme. Virtual screening, followed by docking of obtained hits into the minor groove of B-DNA, gave three potent drugs, which are already approved drugs. The drug having the best fitness and binding score was further docked into the DNA–topoisomerase I cleavable complex. The present study opens up a new dimension in development of drugs for topoisomerase I inhibition. [ABSTRACT FROM AUTHOR]

The present work explores the probable parameters responsible for the potent anticancer activity of tin-based organometallic compounds. The characteristic structural, electronic, and reactivity features of some recently synthesized triorganotin(IV) carboxylates are identified by employing the density functional theory (DFT). The influence of solvent on these parameters is analyzed. In general, the stability of the complex is found to be governed by the donor ligand, alkyl/aryl group at the tin center, and the dielectric of the medium. Gallic acid, best known for its antioxidant and apoptosis inducing ability, forms the most stable complexes with tetrahedral geometry. The NBO analysis, frontier orbitals, and various reactivity indices of the complexes are discussed in detail. The most reactive sites on the organotin complexes are also predicted. [ABSTRACT FROM AUTHOR]

The factors responsible for the potent antioxidant activity of gallic acid (GA) are explored by employing density functional theory (DFT). It is found that the intrinsic characteristic features of the molecule play a significant role in its overall effectiveness as an antioxidant. The arrangement of the three hydroxyl groups with respect to each other imparts efficient antioxidant and antiradical property to GA. The external factors, such as polarity and pH of the reaction medium, also have a significant role to play. The polarity of the medium substantially affects the electron donating ability of GA, whereas the hydrogen atom donating ability is only marginally influenced. GA is a poor electron donor, but it can efficiently donate the hydrogen atom from its para hydroxyl group and effectively quench free radicals. It proves to be a better antiradical agent at the physiological pH, wherein it exists in the monoanionic form. Further, a comparison with other phenolic acids substantiates the importance of the carboxyl and hydroxyl groups in the antiradical activity of GA. [ABSTRACT FROM AUTHOR]

Dihydrofolate reductase (DHFR) is an important enzyme for de novo synthesis of nucleotides in Plasmodium falciparum and it is essential for cell proliferation. DHFR is a well known antimalarial target for drugs like cycloguanil and pyrimethamine which target its inhibition for their pharmacological actions. However, the clinical efficacies of these antimalarial drugs have been compromising due to multiple mutations occurring in DHFR that lead to drug resistance. In this background, we have designed 22 s -triazine compounds using the best five parameters based 3D-QSAR model built by using genetic function approximation. In-silico designed compounds were further filtered to 6 compounds based upon their ADME properties, docking studies and predicted minimum inhibitory concentrations (MIC). Out of 6 compounds, 3 compounds were synthesized in good yield over 95% and characterized using IR, HNMR, CNMR and mass spectroscopic techniques. Parasitemia inhibition assay was used to evaluate the antimalarial activity of s -triazine compounds against 3D7 strain of P. falciparum. All the three compounds ( 7, 13 and 18) showed 30 times higher potency than cycloguanil (standard drug). It was observed that compound 18 was the most active while the compound 13 was the least active. On the closer inspection of physicochemical properties and SAR, it was observed that the presence of electron donating groups, number of hydrogen bond formation, lipophilicity of ligands and coulson charge of nitrogen atom present in the triazine ring enhances the DHFR inhibition significantly. This study will contribute to further endeavours of more potent DHFR inhibitors. [ABSTRACT FROM AUTHOR]

Gallic acid, one of the naturally occurring antioxidants, has been characterized in terms of its structural and chemical properties using the density functional approach. The intramolecular interactions have been identified using natural bond orbital (NBO) analysis. The gallic acid anion and dianion have also been studied for determining the first two pK values. Further, an investigation of the molecular orbitals reveals a dependence of the frontier molecular orbitals on external factors, viz. pH and dielectric of the medium. Consequently, the electronic spectra have been simulated in a range of solvents using steered molecular dynamics. Furthermore, the IR and NMR spectra of the neutral and the deprotonated state have been simulated. Additionally, the spectra have been experimentally recorded to validate the methodology followed. The present work also examines the variation in global and local reactivities of gallic acid under the influence of external factors. Each atom has been quantitatively assessed for its susceptibility towards nucleophilic, electrophilic, and radical attack. [ABSTRACT FROM AUTHOR]

The Schmidt reaction is the acid-catalyzed analogue of the Curtius reaction and is extensively used in organic synthesis. In this work, the mechanism of this reaction has been explored using DFT calculations at the B3LYP/6-311+G(d,p) level. Protonated formyl azide may undergo rearrangement to the product, protonated isocyanic acid, with simultaneous extrusion of molecular nitrogen (concerted mechanism), or undergo rearrangement to the anti conformer, followed by removal of nitrogen to form the nitrenium ion, which then rearranges to the final product, protonated isocyanic acid (step-wise mechanism). Like the Curtius reaction, it is found that the concerted pathway is definitely preferred. The key role of acidification in decreasing the overall energy barrier is more highlighted in case of phenyl substitution, with negligible effect on the lower homologues. For methoxy and amine substituents, there is very little difference in the activation energies of the concerted and step-wise reactions, with the former being still slightly preferred. Unlike the parent compound, the rearrangement of substituted nitrenium ion in some cases involves side reactions like C-H insertion and cyclization. [ABSTRACT FROM AUTHOR]

1,4-Dihydropyridines are well-known calcium channel blockers, but variations in the substituents attached to the ring have resulted in their role reversal making them calcium channel activators in some cases. We describe the microwave-assisted eco-friendly approach for the synthesis of pyranopyrazole-1,4-dihydropyridines, a new class of 1,4-DHPs, under solvent-free conditions in good yield, and screen them for various in silico, in vitro and in vivo activities. The in vivo experimentation results show that the compounds possess positive inotropic effect, and the docking results validate their good binding with calcium channels. Compounds 7c, 7g and 7i appear to be the most effective positive inotropes, even at low doses, and bind with the calcium channels even more strongly than Bay K 8644, a well-known calcium channel activator. The chronotropic effect for the new compounds was also studied. The target and off-target affinity profiling supported the in vivo results and revealed that the hybridized pyranopyrazole dihydropyridine scaffold has delivered new moderate hits, to be optimized, for the cytochrome P450 3A4 enzymes, opening avenues for combined pharmacological activity through standard structural modification. Graphical Abstract : [ABSTRACT FROM AUTHOR]

In this work, tri-octyl phosphine/tri-octyl phosphine oxide (TOPO)-capped cadmium selenide (CdSe) quantum dots (QDs) of varied sizes (5–9 nm), prepared by varying the input Cd:Se precursor ratio using chemical route, were dispersed in conducting polymer matrices viz. poly[2-methoxy, 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT). By using a binary solvent mixture (pyridine–chloroform), homogeneous dispersion of CdSe nanocrystals in polymers (MEH-PPV, P3HT) could be realized. The properties of the resulting dispersions could be tailored by the composition and concentration of QDs in polymer. The emission and structural properties of polymer–CdSe nanocomposites are found to be dependent on the crystallite size and morphology of CdSe nanocrystallites. An effective quenching of photoluminescence emission in the polymer nanocomposite was observed for smaller CdSe quantum dots (size ∼6 nm) as compared to larger CdSe quantum dots (size ∼9 nm), thus ensuring efficient charge transfer process across the polymer–CdSe interface in the former case. The incomplete quenching, particularly for MEH-PPV:CdSe nanocomposites, could be as a result of insufficient coverage of polymers on the surface of CdSe nanocrystallites, mainly due to phase segregation for TOPO-stripped CdSe nanocrystallites. The superior morphology and optical properties of polymer nanocomposite (P3HT:CdSe QDs) could play a pivotal role for the realization of effective charge separation and transport in hybrid solar cells. [ABSTRACT FROM AUTHOR]

In this work, polysorbate surfactants with same functional groups but with varying molecular masses (Tween-80, Tween-40 and Tween-20) in different concentrations (0.1% to 20% w/w) were used to study the effect of the length of the surfactant chain on the luminescence of the entrapped TOPO-capped CdSe nanocrystals. Various phospholipids with different functional headgroups such as ethylene glycol (-PEG) and amine (-NH2) were used to improve biocompatibility and provide sites for bioconjugation respectively. It is understood that that the hydrophobic ends of the surfactant binds with the water repelling groups of the cap layer, thus modifying the CdSe cap layer and making it soluble in aqueous media. It was observed that the PL emission intensity of CdSe increases with increase in concentration of Tween-series surfactant unlike in the case of thiol-coated CdSe nanoparticles. However, higher PL intensity was obtained in the case of stoichiometric CdSe with Tween-40 corresponding to 20% w/w. The efficient PL sustainability of water-soluble CdSe QD’s can be attributed to the simpler chain structure of Tween-40 surfactant resulting in better passivation of the micelle. [ABSTRACT FROM AUTHOR]

Semiempirical SCF-MO studies of tautomerism in alloxan preclude the possibility of direct proton transfer in the gas phase due to the strain in the four-centred transition state, in which the proton being transferred is forced to come close to the positively charged carbon atom at the opposite corner of the four-membered ring. However, in aqueous solution, the activation barrier reduces appreciably, not only due to reduction in strain, but also due to charge separation in the transition state, which is stabilized due to ionic resonance. The N-H bond is almost broken, while the O-H bond is only partially formed in the transition state. The other stabilizing effect in aqueous solution is due to bulk solvent dielectric effects, which stabilize the transition state to a greater extent due to its higher dipole moment. Although the transition states for proton transfer to the neighbouring oxygen atoms on either side have comparable energies, as the mechanisms of proton transfer leading to the formation of the 2-hydroxy and 4-hydroxy tautomers are similar, bulk solvent effects are larger in the latter due to the higher dipole moment of the transition state. The reason is the almost complete separation of the two entities, i.e. the alloxan anion and the hydronium ion in the latter case, indicating that in this case a dissociative mechanism of the kind encountered in acid-base equilibria is operating. [ABSTRACT FROM AUTHOR]

The electronic structure of barbituric acid has been investigated, keeping in mind the possibility of tautomerism. It has been found that the triketo form is the most stable, followed by the 4-hydroxy tautomer. The difference in their stabilities decreases on substitution at C. Substituents that allow a greater degree of delocalization with the ring system (nitro, bromo, thiol) stabilize the 4-hydroxy tautomer to a greater extent since it is planar. The AM1 method is found to be the best suited for studying the electronic structure of barbituric acid, as it gives the best agreement with the experimental geometries. Of the other two methods investigated, MNDO gives erroneous results for relative energies, while PM3 gives unsatisfactory geometries. The stabilities of the charged species resulting from deprotonation, and the radicals resulting from the removal of a hydrogen atom by heat treatment or irradiation with gamma rays, have also been investigated. Their electronic structures are also discussed. [ABSTRACT FROM AUTHOR]

The current study reports a detailed investigation of the adsorption behavior of Mo4, Mo3Co, Mo2Co2, and MoCo3 clusters on graphene by studying their binding energy, charge transfer, band gap, electron density difference plots, and density of states (DOS) plots. The magnetic properties of these surfaces have also been reported. Owing to the strong adsorption power of small metal cluster-decorated graphene surfaces, we have further utilized the Mo4-decorated graphene for the adsorption of SO2F2 and SOF2 gases, which are two gases that are released from the decomposition of SF6, a gas used as an insulating medium in gas-insulated switchgear. The use of Mo4-decorated graphene surface resulted in the dissociative adsorption of these gases with high adsorption energy and large charge transfer. In contrast, only physisorption occurred on pristine graphene. Further details of the adsorption were investigated by studying the DOS and partial DOS (PDOS) plots before and after adsorption. The band gap and electron density difference plots have also been reported. Graphical abstract [ABSTRACT FROM AUTHOR]

A computational study on the structural and electronic properties of a special class of artificial atoms, known as quantum dots, has been carried out. These are semiconductors with unique optical and electronic properties and have been widely used in various applications, such as bio-sensing, bio-imaging, and so on. We have considered quantum dots belonging to II-VI types of semiconductors, due to their wide band gap, possession of large exciton binding energies and unique optical and electronic properties. We have studied their applications as chemical ion sensors by beginning with the study of the ion sensing ability of (CdSe)n (n = 3, 6, 9 which are in the size range of ~ 0.24, 0.49, 0.74 nm, respectively) quantum dots for cations of the zinc triad, namely Zn2+, Cd2+, Hg2+, and various anions of biological and environmental importance, and studied the effect of increasing number of rings on their ion sensing ability. The various structural, electronic, and optical properties, their interaction energies, and charge transfer on interaction with metal ions and anions have been calculated and reported. Our studies indicate that the CdSe quantum dots can be employed as sensors for both divalent cations and anions, but they can sense cations better than anions. [ABSTRACT FROM AUTHOR]