Amorphous Carbon Nanoparticles Research Articles

Amorphous Cobalt-Impregnated Nitrogen-Doped Carbon Encapsulation Nanochain Enhances Long-Lasting Electrochemical Water Splitting.

Electrochemical water splitting (EWS) is a promising way to attain H2, which has been deemed an ideal substitution for fossil fuels because of renewable and eco-friendly benefits. Developing an amorphous-based simple and structurally flexible non-noble catalyst to offer high performance for commercial applications has become a current interest. Amorphous cobalt-anchored nitrogen-doped carbon nanoparticles (Co@NC-NPs) were designed to have a low overpotential and Tafel as a bifunctional electrocatalyst (HER - 142 mV/80 mV dec-1 and OER - 250 mV/72 mV dec-1) to achieve 10 mA cm-2 in 1.0 KOH. FE-SEM and HR-TEM described the interconnected nanochain morphology and purity of Co@NC-NPs electrocatalyst, which were confirmed by EDX and elemental mapping. In a full cell water electrolyzer, Co@NC-NPs(+,-) may act as an anode and cathode electrode material to achieve 1.60 V @ 10 mA cm-2 in a wide pH. The efficient Co@NC-NPs are stable for 100 h without obvious recession. In solar cell applications, Co@NC-NPs(+,-) catalyst was employed as both positive and negative terminals and evolved enormous bubbles of O2 and H2. As previously mentioned, we covered the amorphization strategy with the optimistic role of structural flexibility and defects to enrich the active sites to improve the electrocatalytic stability. As a promising opinion, the amorphous electrocatalyst provides ultraefficiency for forthcoming developments in EWS.

Synthesis and Characterization of Vanadium Nitride/Carbon Nanocomposites.

The present work focuses on the synthesis of a vanadium nitride (VN)/carbon nanocomposite material via the thermal decomposition of vanadyl phthalocyanine (VOPC). The morphology and chemical structure of the synthesized compounds were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoemission spectroscopy (XPS). The successful syntheses of the VOPC and non-metalated phthalocyanine (H2PC) precursors were confirmed using FTIR and XRD. The VN particles present a needle-like morphology in the VN synthesized by the sol-gel method. The morphology of the VN/C composite material exhibited small clusters of VN particles. The XRD analysis of the thermally decomposed VOPC indicated a mixture of amorphous carbon and VN nanoparticles (VN(TD)) with a cubic structure in the space group FM-3M consistent with that of VN. The XPS results confirmed the presence of V(III)-N bonds in the resultant material, indicating the formation of a VN/C nanocomposite. The VN/C nanocomposite synthesized through thermal decomposition exhibited a high carbon content and a cluster-like distribution of VN particles. The VN/C nanocomposite was used as an anode material in LIBs, which delivered a specific capacity of 307 mAh g-1 after 100 cycles and an excellent Coulombic efficiency of 99.8 at the 100th cycle.

Acoustic shock wave processing on amorphous carbon quantum dots – correlation between spectroscopic-morphological–magnetic and electrical conductivity properties

In this context, we report the acoustic shock wave processing on amorphous Carbon quantum dots (a-CQD) such that its degree of graphitization and magnetic properties are analyzed. Analytical techniques such as the Raman spectrometer, high resonation–transmission electron microscopy (HR-TEM) and vibrating sample magnetometer (VSM) are utilized to understand the structural, morphological and magnetic properties changes under shocked conditions. The Raman spectroscopic data reveal that the ID/IG ratio is slightly reduced under shocked conditions and the observed values are 0.78, 0.77 and 0.75 for the respective 0, 150 and 300 shocked conditions. The formation of ultra-short-range graphitic nanostructures is confirmed by HR-TEM results at the 300-shocked condition. The most convincing and supporting results for the enhancement of the degree of graphitization are found by the outcome of the magnetic properties such that the saturation magnetization (Ms) is found to be linearly reduced with respect to the number of shock pulses and the observed values are 0.869, 0.757 and 0.710 emu/g for the 0, 150 and 300 shocked conditions, respectively. The electrical resistance of the a-CQD is found to be linearly reduced with respect to the number of shock pulses due to the reduction of sp3 carbon networks. The formation of crystalline graphitic nanostructures in amorphous CQD is explained on the basis of the hot-spot nucleation mechanism. Based on the obtained Raman, HR-TEM and VSM results, during the shocked conditions, slight enhancement of the graphitization is observed; however, from the structural stability point of view, the Carbon dots have high shock resistance than that of the amorphous carbon nanoparticles, multi-wall carbon nanotubes, and reduced graphene oxide nanoparticles. Hence, the title quantum dots can be strongly considered for the applications of device fabrication.

Preparation of a highly specific and sensitive monoclonal antibody against tilmicosin and its application in lateral flow immunoassay

To reduce the false positive results caused by cross reactivity of the antibodies with other structural analogues, it is crucial to prepare a high specificity and sensitivity antibody against target for developing an accurate immunoassay. In this study, tilmicosin (TM) was selected as a model molecule. Firstly, two-dimensional similarity, electrostatic potential energy, mulliken atomic charges and overlapping of different haptens with TM were calculated using Gaussian 09W and Discovery studio, and the newly designed TM-HS was selected as the optimal hapten. Furthermore, a monoclonal antibody (mAb 12C8) was produced with the half maximal inhibitory concentration (IC50) of 0.36 ng/mL, and negligible cross-reactivity (CR) with other antibiotics. Finally, a lateral flow immunoassay (LFA) for the detection of TM based on amorphous carbon nanoparticles (ACNPs) labeled mAb 12C8 was developed by the reflectance value under natural light. The recoveries of TM ranged from 83.18% to 103.25% with a coefficient of variation (CV) < 12.47%. The results showed that the cut-off value of TM in milk samples was 1 ng/mL, and the limits of detection (LODs) for chicken muscle, bovine muscle, porcine muscle and porcine liver samples were 5.23, 5.98, 6.85 and 7.31 μg/kg, respectively. In addition, 40 real samples were tested by the LFA, and the detection results were consisted with that of high-performance liquid chromatography-UV detector (HPLC–UV). Those results indicated that the developed LFA is an accurate and useful tool for on-site screening of TM in milk and animal tissues.

Production of monoclonal antibody against tylosin and tilmicosin with homogeneous cross-reactivity and its application in lateral flow immunoassay.

To avoid false negative results due to the low cross-reactivity rate (CR) in rapid immunoassay, a group-specific antibody with homogeneous CR toward target compounds is needed for accuracy. In this study, tylosin (TYL) and tilmicosin (TM) were selected as model molecules. Firstly, two-dimensional similarity, electrostatic potential energy, spatial conformation and charge distribution of the haptens TYL-CMO, TYL-6-ACA, TYL-4-APA, TYL-CHO and DES-CMO and target compounds of TYL and TM were obtained using Gaussian 09W and Discovery Studio. The optimal hapten was DES-CMO because it is the most similar to TYL and TM. Subsequently, the mAb 14D5 cell line was obtained with IC50 values of 1.59 and 1.72ng/mL for TYL and TM, respectively, and a CR of 92.44%. Finally, amorphous carbon nanoparticles (ACNPs) were conjugated with mAb 14D5 to develop an accurate lateral flow immunoassay (LFA) for detection of TYL and TM by the reflectance value under natural light. The recoveries of TYL and TM ranged from 77.18 to 112.04% with coefficient of variation < 13.43%. The cut-off value in milk samples was 8ng/mL, and the limits of detection were 11.44, 15.96, 22.29 and 25.53μg/kg for chicken muscle, bovine muscle, porcine muscle and porcine liver samples, respectively, and the results being consistent with HPLC-UV. The results suggest that the developed LFA is accurate and potentially useful for on-site screening of TYL and TM in milk and animal tissue samples.

Acoustic shock wave-induced short-range ordered graphitic domains in amorphous carbon nanoparticles and correlation between magnetic response and local atomic structures

Over the years, a wide range of spectral research has been carried out on various carbon forms to explore deeply their structure-property relationship. The structural stability of carbon allotropies remains to be a challenging endeavor yet to be achieved under extreme conditions, especially under acoustical shocked conditions. From the experimental findings, we report the acoustic shock wave response of the amorphous carbon nanoparticles and the resultant degree of crystalline nature, morphological characteristics and magnetic response. Moreover, analytical techniques such as X-ray diffractometry (XRD), Raman spectrometer, High resolution transmission electron microscopy (HR-TEM) and vibrational sample magnetometer (VSM) have been employed to arrive at the relationships of structure – morphology – magnetic properties under shocked conditions. Interestingly, under shocked conditions (0, 250, 500 and 750 shocks), compelling evidence has been found for the short-range amorphous pockets which turn into spatially short-range ordered graphitic domains within the sphere-shaped amorphous nanoparticles whereby the obtained values of the ratio ID/IG of the samples are 0.94, 0.93, 0.95 and 1.01 for 0, 250, 500 and 750 shocked conditions, respectively. Moreover, the saturation magnetization is found to have reduced in the base of the local atomic ordering and the obtained values are found to be 1, 0.64, 0.41, 0.725 emu/g for 0, 250, 500 and 750 shocked conditions, respectively. The structure-property relationship is to be elaborated in the upcoming sections.

Effects of carbon nanomaterials on interfacial structure and mechanical properties of high temperature Ti matrix composites

TiC is widely used as an ideal reinforcement to strengthen titanium matrix composites (TMCs). The morphology, size and distribution of TiC and the interfacial structure of TiC-Ti are crucial to obtain good mechanical properties of titanium matrix composites. These are keys to achieve superior strength and good ductility in titanium matrix composites. Hence, we investigated the effects of TiC generated in situ from different carbon sources (i.e., amorphous carbon nanoparticles, reduced graphene oxide and graphene nanoparticles) on the interfacial structure and mechanical properties of Ti60 alloy. Amorphous carbon nanoparticles (ACNS), reduced graphene oxide (rGO) and graphene nanoparticles (GNPs) reinforced Ti60 composites were prepared using spark plasma sintering (SPS). Among the three carbon nanomaterials, ACNs and rGO reacted with Ti60 matrix to form TiC, facilitating interfacial bonding. GNPs were not completely reacted with Ti60 matrix and residual on the interface owing to its poor dispersion effect, resulting in interfacial structure defects. The mechanical properties of the ACNs/Ti60 and rGO/Ti60 composites are high than GNPs/Ti60 composites. The ultimate tensile strengths of ACNs/Ti60 composites were 1173.49 MPa, 702.96 MPa and 653.13 MPa at room temperature, 600 °C and 650 °C, respectively, improving by 17.63%, 14.13% and 16.21% over Ti60, respectively. The superior mechanical properties are attributed to the fact that ACNs and rGO are more easily dispersed in the Ti60 matrix. The reaction activity of ACNs and rGO are higher than GNPs, and more TiC phase content was formed after sintering. TiC formed a semi-coherent interface with the Ti60 matrix, promoting the interfacial bonding strength. It also played a role in grain refinement and load transfer effect. This work helps to further elucidate the reinforcement effect of TiC formed by different carbon nanomaterials on TMC.

A neural network approach to kinetic Mie polarimetry for particle size diagnostics in nanodusty plasmas

The analysis of the size of nanoparticles is an essential task in plasma technology and dusty plasmas. Light scattering techniques, based on Mie theory, can be used as a non-invasive and in-situ diagnostic tool for this purpose. However, the standard back-calculation methods require expertise from the user. To address this, we introduce a neural network that performs the same task. We discuss how we set up and trained the network to analyze the size of plasma-grown amorphous carbon nanoparticles (a:C–H) with a refractive index n in the range of real(n) = and imag(n) = and a radius of up to several hundred nanometers, depending on the used wavelength. The diagnostic approach is kinetic, which means that the particles need to change in size due to growth or etching. An uncertainty analysis as well as a test with experimental data are presented. Our neural network achieves results that agree with those of prior fitting algorithms while offering higher methodical stability. The model also holds a major advantage in terms of computing speed and automation.

A highly sensitive lateral flow immunoassay based on a group-specific monoclonal antibody and amorphous carbon nanoparticles for detection of sulfonamides in milk.

To meet high-throughput screening of the residues of sulfonamides (SAs) with high sensitivity toward sulfamethazine (SM2) in milk samples, a new highly sensitive lateral flow immunoassay (LFA) based on amorphous carbon nanoparticles (ACNs) was developed. First, a group-specific monoclonal antibody 10H7 (mAb 10H7) that could recognize 25 SAs with high sensitivity toward SM2 (IC50 value of 0.18ng/mL) was prepared based on H1 as an immune hapten and H4 as a heterologous coating hapten. Then, mAb 10H7 was conjugated to ACNs as an immune probe for LFA development. Under the optimized conditions, the LFA could detect 25 SAs with the cut-off value toward SM2 of 2ng/mL, which could meet the requirement for detection of SAs. In addition, the LFA developed was also used for screening SAs' residues in real milk samples, withresults beingconsistent with HPLC-MS/MS. Thus, this LFA can be used as a high-throughput screening tool for detection of SAs.

Synthesis and analysis of nanostructured graphene oxide

Work has been carried out to improve the method for obtaining and further oxidizing Graphene Oxide (GO) to obtain functionalized layers with a large number of active centres. We have determined that with an increase in the amount of H2O2 in the synthesis, it significantly increases the efficiency of the oxidation process and increases the number of functional groups, while the amount of NaNO3 and KMnO4 remains unchanged. Fourier-Transform Infrared Spectroscopy (FTIR), X-ray analysis, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) analyses were carried out. Based on the FTIR result, all putative functional groups for a given material (GO) were determined, such as carbonyl, hydroxyl, ketone and epoxy groups which chemically bonded with graphene. SEM and TEM drawings were analysed, which gave a broad understanding of the morphology of GO nanostructures and, based on these drawings, it is fashionable to say that the material is semi-crystalline with the presence of such byproducts as amorphous carbon nanoparticles. Based on the EDX analysis, it was proved that this nano-structured material does not have third-party products.

Low-temperature organic solvent-based synthesis of amorphous porous carbon nanoparticles with high specific surface area at ambient atmosphere

The conventional synthesis of porous carbon materials is primarily relied on the activation and template process. This work successfully develops a one-step method for preparing amorphous porous carbon nanoparticles (APCNs) with a high specific surface area (SSA) in organic solvents under ambient atmosphere. The APCNs are formed mainly by the reaction of ferrocene with ammonium chloride at only 180 °C for 1 h in different solvents. Several ferrocene derivatives and KOH activation are also utilized to improve the textural properties of the APCNs. It is found that the high solubility of (C 5 H 5 ) 2 Fe and FeCl 3 ·6H 2 O in a solvent is the most essential factor associated with the decrease of carbon nanoparticle size. The smaller the nanoparticle size, the larger the SSA of APCNs. The APCNs prepared in phenoxyethanol have a median size of 32.74 nm, exhibiting an SSA of 689 m 2 /g. The high solubility of NH 4 Cl can also contribute to reducing the nanoparticle size. The binary solvent consisting of phenoxyethanol and glycol has an excellent solubility for (C 5 H 5 ) 2 Fe, FeCl 3 ·6H 2 O, and NH 4 Cl, in which the prepared APCNs have a median size 11.48 nm and a higher SSA of 936 m 2 /g. Besides, the benzoyl substituted group on the cyclopentadiene can facilitate formation of small mesopores. The oxygen and nitrogen are in situ doped in the APCNs. Activation is also effective, and the SSA of APCNs reaches a maximum value of 1575 m 2 /g at a KOH ratio of 2:1. The solvent-based synthesis is unique and competitive in terms of high efficiency and energy conservation. • A novel liquid-phase method for preparing amorphous porous carbon nanoparticles is developed based on an oxidation mechanism. • The synthesis is carried out at ambient atmosphere at 180 °C. • The specific surface area and pore volume are 936.11 m 2 /g and 1.45 cm 3 /g, respectively.

Facile synthesis of yolk-shell Si@void@C nanoparticles with 3D conducting networks as free-standing anodes in lithium-ion batteries

The low cost and high performance via a simple way of fabrication are considerable challenges for Si-based anode in the application of lithium-ion batteries. In this study, we synthesize a novel free-standing Si/C anode, consisting of yolk (Si)-shell (amorphous carbon) nanoparticles and carbon nanofibers (denoted as Si@void@C/CNFs), via a facile route of template removal and electrospun. The designed yolk-shell structure help buffer the volume expansion of silicon during the discharge/charge cycles, and the intertwined CNFs are conducive to electron fast transmission and guarantee structural integrity. As expected, with a low Si content (∼23 wt%), the self-supporting electrode of Si@void@C/CNFs exhibits a high specific capacity of ∼627.5 mAh g−1 as well as 69.3% capacity retention at 0.1 A g−1 after 100 cycles, better than Si@C/CNFs (20%) and Si/CNFs (9.5%) electrodes. The superior performance of Si@void@C/CNFs indicates that it is an attractive anode material for the practical application of Lithium-ion batteries.

A Study of the Biocompatibility of a Nanostructured Coating Based on Amorphous Carbon and Gold Nanoparticles in an Experimental In Vivo Model

A Study of the Biocompatibility of a Nanostructured Coating Based on Amorphous Carbon and Gold Nanoparticles in an Experimental In Vivo Model

Phase-Controlled Synthesis of Nickel-Iron Nitride Nanocrystals Armored with Amorphous N-Doped Carbon Nanoparticles Nanocubes for Enhanced Overall Water Splitting.

Transition metal nitrides (TMNs) nanostructures possess distinctive electronic, optical, and catalytic properties, showing great promise to apply in clean energy, optoelectronics, and catalysis fields. Nonetheless, phase-regulation of NiFe-bimetallic nitrides nanocrystals or nanohybrid architectures confronts challenges and their electrocatalytic overall water splitting (OWS) performances are underexplored. Herein, novel pure-phase Ni2+ x Fe2- x N nanocrystals armored with amorphous N-doped carbon (NC) nanoparticles nanocubes (NPNCs) are obtained by controllable nitridation of NiFe-Prussian-blue analogues derived oxides/NC NPNCs under Ar/NH3 atmosphere. Such Ni2+ x Fe2- x N/NC NPNCs possess mesoporous structures and show enhanced electrocatalytic activity in 1m KOH electrolyte with the overpotential of 101 and 270mV to attain 10 and 50mAcm-2 current toward hydrogen and oxygen evolution reactions, outperforming their counterparts (mixed-phase NiFe2 O4 /Ni3 FeN/NC and NiFe oxides/NC NPNCs). Remarkably, utilizing them as bifunctional catalysts, the assembled Ni2+ x Fe2- x N/NC||Ni2+ x Fe2- x N/NC electrolyzer only needs 1.51V cell voltage for driving OWS to approach 10mAcm-2 water-splitting current, exceeding their counterparts and the-state-of-art reported bifunctional catalysts-based devices, and Pt/C||IrO2 couples. Additionally, the Ni2+ x Fe2- x N/NC||Ni2+ x Fe2- x N/NC manifests excellent durability for OWS. The findings presented here may spur the development of advanced TMNs nanostructures by combining phase, structure engineering, and hybridization strategies and stimulate their applications toward OWS or other clean energy fields.

Development of a sensitive monoclonal antibody-based immunochromatographic strip for neomycin detection in milk

ABSTRACT To improve the detection sensitivity of neomycin (NEO) in milk, we produced a sensitive monoclonal antibody (mAb) against NEO and developed a lateral flow immunoassay based on amorphous carbon nanoparticles (ACNPs-LFA). First, we conjugated NEO to carrier protein to prepare mAbs. We obtained six mAbs: mAb 1C6, mAb 1D3, mAb 2D3, mAb 4D5, mAb 5D1, and mAb 5H1. We characterised the mAbs by indirect competitive enzyme-linked immunosorbent assay and selected the most sensitive mAb based on the half-maximal inhibitory concentration (IC50). We selected mAb 4D5 (IC50 = 0.15 ng/mL) for the development of LFA. MAb 4D5 was labelled with ACNPs (ACNPs-mAb 4D5) by electrostatic absorption. Under optimised conditions, 5.4 μg mAb 4D5 coupling with 1 mL ACNPs, NEO-OVA at concentration of 80 μg/mL, 3 μL ACNPs-mAb 4D5 were used to develop LFA. The cut-off value was 8 ng/mL. Therefore, our developed ACNPs-LFA is suitable for on-site detection of NEO residues.

A comparative study of “turn-off” mode and “turn-on” mode lateral flow immunoassay for T-2 toxin detection

The “turn-off” mode lateral flow immunoassay (LFA) based on the conventional competitive format and “turn-on” mode LFA mainly determined by inner filter effect (IFE-LFA) were objectively compared using T-2 toxin as a model molecule and T-2-BSA and anti-T-2 monoclonal antibody as immunocomplex pairs to improve the sensitivity of the LFA. First, Au nanoparticles (Au NPs), amorphous carbon nanoparticles (ACNPs), quantum dots nanospheres (QDs), and time-resolved fluorescent microspheres (TRFMs) were selected as labels for developing the “turn-off” mode LFAs (Au NPs-LFA, ACNPs-LFA, QDs-LFA, and TRFMs-LFA, respectively). Thereafter, Au NPs and ACNPs were used as absorbers, and QDs and TRFMs were selected as fluorescers, for preparing the “turn-on” mode IFE-LFAs (IFE-LFA based on Au NPs as absorbers and QDs as fluorescers [Au NPs-mAb-QDs-BSA], IFE-LFA based on Au NPs as absorbers and TRFMs as fluorescers [Au NPs-mAb-TRFMs-BSA], IFE-LFA based on ACNPs as absorbers and QDs as fluorescers [ACNPs-mAb-QDs-BSA], and IFE-LFA based on ACNPs as absorbers and TRFMs as fluorescers [ACNPs-mAb-TRFMs-BSA]). Under optimized conditions, the naked-eye observation cut-off values for the aforementioned eight LFAs were 4, 2, 2, 2, 3, 2, 1.5, and 1 ng/mL, with quantitative limit of detection values of 0.50, 0.23, 0.24, 0.23, 0.47, 0.45, 0.27, and 0.22 ng/mL, respectively. Among all LFAs, ACNPs-mAb-TRFMs-BSA showed the highest sensitivity. The results of this study provide a perspective for improving the sensitivity of the LFAs to meet the requirements of on-site screening for trace substances.

Growth and treatment of hydrogenated amorphous carbon nanoparticles in a low‐pressure plasma

AbstractA parallel‐plate, low‐pressure plasma for fundamental nanodusty plasma research is used to grow hydrogenated amorphous carbon nanoparticles using an argon‐acetylene gas mixture. The particles stay confined in the volume of the argon plasma after turning off the gas flow and the effects of prolonged treatment with noble gas (Ar) and reactive gas mixtures (Ar/, Ar/, or Ar/) are investigated using in situ infrared absorption spectroscopy. Additionally, ex situ scanning electron microscopy imaging of extracted nanoparticles is used to analyze their size and surface morphology. In 45 min of argon treatment, a size increase of about 50% is seen together with a decrease in bonds and an increase in C═O bonds, indicating incorporation of oxygen from gas impurities into the particle material. All reactive gas mixtures lead to the expected etching of the nanoparticle material without any exchange reactions between gas‐phase deuterium and surface‐bonded hydrogen atoms. These results are important for in situ studies of nanoparticle clouds such as dust density wave diagnostics, but they also provide fundamental information about plasma interaction with a‐C:H material.

Amorphous carbon based nanofluids for direct radiative absorption in solar thermal concentrators – Experimental and computational study

Directly solar radiation absorbing nanofluids have the potential to absorb a wide spectrum of solar radiation and displace selectively coated metallic receivers in solar thermal collectors. Parameters including nanoparticle concentration, synthesis and storage conditions, can influence their long-term usage. In this study, 60 min was found to be optimal sonication duration to synthesise a uniform suspension of nanofluid containing amorphous-carbon nanoparticles and ethylene glycol as base fluid. Nanoparticle concentration can be used to tune extinction coefficient of nanofluid in the range of 75–400 m−1 for wavelength range of 320–1000 nm. Long-term stability and high temperature studies showed a time and temperature dependent increase in transmittance of nanofluid which is restored by 5 min of stirring. Computational modelling highlighted the role of incident intensity, nanoparticle concentration as well as inlet flow rate on receiver exit temperature. A ray-optics model employing weather data for Delhi (India) can predict the optical efficiency of an Asymmetric Compound Parabolic Concentrator solar collector. This combined approach can enable to predict the flow rate required to achieve a desired supply temperature at target locations. This rational framework combining experimental and computational approaches can be used to identify design parameters relevant for application of nanofluids in thermal collectors.

Evolution of UV/VIS Photoluminescence of Aged Zn(acac)2 Solutions in Correlation with Carbon Precipitation

Photoluminescent carbon nanodots (CDs), a new class of inorganic nanocarbon materials, have become a significant segments of luminescent nanomaterials in last decade. However mechanism of light emission and detailed identification of the light emitting centers is still debated. A huge number of synthesis methods were suggested, however few of them allow to monitor formation of the CDs on the early stage and development in progress. Recently we have found that zinc acetylacetonat (Zn(acac)2) in ethanol solutions tends to be hydrolysed under room temperature laboratory conditions resulting in gradual conversion of colorless and non luminescent solution to yellowish liquid accompanied by cedimentation of nonluminescent amorphous ZnO:OH. The yellow component of the solution has been identified as dispersion of carbon precipitates. The most important is that the process of hydrolysis in very slow with changing color and PL development within several months. Such a slow process allows following the details of PL development and evolution in time correlation with carbon precipitation.Ethanol solutions of Zn(acac)2 with concentrations in range of 0.1-4.0 % were prepared and their photoluminescence was monitored for time period of several months. It has been found that early stage of carbon precipitation is resulted in development of relatively narrow PL band with maximum at about 400 nm and corresponding excitation band at 360 nm. The spectrum of the emission band is excitation independent as well as excitation band is not dependent on emission wavelength. In the course of further aging and carbon precipitation the PL band is broaden and shifted to visible range with maximum intensity in range of 420-500 nm depending on excitation wavelength. Detailed emission/excitation study revealed that the visible emission band is composed of at list two components centered at about 420-450 nm and 500 nm, with the corresponding excitation bands at 365 nm and 420 nm. Time-resolved photoluminescence spectroscopy showed that the decay of low energy emission band follows the classical mono-exponential low with the characteristic time of several nanoseconds, while the behavior of high energy component can be described by the stretched exponential low with the average decay time of several nanoseconds. PL data is summarized and discussed in the terms of subnanometer molecular-like carbon emitters and core/shell structural model of amorphous carbon nanoparticles.

Adulteration of cow’s milk with buffalo’s milk detected by an on-site carbon nanoparticles-based lateral flow immunoassay

A competitive lateral flow immunoassay using amorphous carbon nanoparticles (CNPs) and non-immunoglobulin antigen has been developed for the rapid detection of adulteration of cow’s milk with buffalo’s milk. Purified polyclonal antibodies against a specific buffalo's milk protein fraction were conjugated to CNPs and sprayed on a conjugate pad. The test line consisted of buffalo's skimmed milk proteins (1.6 μg/cm), while the control line contained anti-rabbit antibodies raised in goat (0.5 μg/cm). In the test procedure milk sample is mixed with 100 mM borate buffer (pH 8.8 containing 1% BSA and 0.05% Tween 20) and pipetted onto the sample-cum-conjugate pad. A black/grey test line can be observed if the sample is free from buffalo's milk. The sensitivity of the test i.e. no visible test line is 5% adulteration of cow's milk with buffalo's milk. The test has applicability at the milk receiving stations and can be applied to heated milk samples.