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In this paper, ultra-low level selective detection of bovine serum albumin (BSA) has been demonstrated, based on chemically derived graphene i.e., reduced graphene oxide (RGO) nanosheets. The working principle of the sensor is based upon change in conductance of the RGO nanosheets with different concentration of BSA. The change in conductance is based on the charge transfer between BSA and functional groups of RGO. The morphological and structural characterizations of RGO nanosheets were carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Raman spectroscopy is performed to further validate the interaction between RGO sensing layer and BSA molecules. Electrical impedance spectroscopy is performed to observe the impedance variation when BSA interacts with RGO. The sensor device exhibits sensitivity of 10 nA/pM. The lower limit of detection (LOD) of the sensor is found to be 1 pM and response time around 35 s, confirming very high sensitivity for BSA. All electrical (current-voltage) measurements were carried out at 2 V bias for low power operation. The sensor exhibits highest sensitivity at 30 °C and for RGO thickness ~4 nm. The RGO based sensor device is selective towards BSA when compared to proteins like L-Histidine, HSA, BHB and Biotin. Our results suggest that RGO based devices are promising for low-cost, portable and real time detection of BSA at room temperature.

Functionalized carbon nanotubes are recommended as potential drug-delivery tools due to their reduced toxicity and increased solubility or wettability. However, their applications are still restricted because of their dose- and time-dependent toxicity. The conflicting reports regarding toxicity assays of pristine and functionalized multiwalled carbon nanotubes (MWCNTs) in different in vivo and in vitro models inspired us to design a safe drug-releasing device and investigate its applicability in a widely used human-analogous in vivo model. We thereby propose a biocompatible drug-delivery vector that is nontoxic even at higher doses in the Caenorhabditis elegans nematode model. We further carried out a comparative analysis of the various biocompatibility assays of MWCNTs functionalized with inorganic and organic molecules. Synthetic single-stranded DNA (ssDNA) oligonucleotide (5′-GGG-GGG-GGG-G-3′)-functionalized MWCNTs were found to be the most biocompatible and nontoxic even at higher doses (320 µg/mL) of MWCNTs. In contrast, pristine and NH2-functionalized MWCNT were proven to be toxic at lower doses (20–160 µg/mL) of MWCNTs based on survival, locomotion, reproductive potential, and oxidative-stress-related endpoints. Thus, the order of cytotoxicity in animals was observed to be as follows: pristine MWCNTs > NH2-functionalized MWCNTs > ssDNA-functionalized MWCNT.

Single-Walled Carbon Nanotubes (SWCNTs) are widely used as potential carriers in drug delivery systems. The objective of this work was to observe the effects of pristine, and single-stranded DNA oligonucleotide functionalized SWCNT over the locomotion pattern in the nematode model, Caenorhabditis elegans. The implication of ssDNA in the as-modified SWCNT has been understood in terms of lowering the toxic effects of the pristine SWCNT and thereby normalizing the altered navigation pattern of the worms. Chemotaxis assay displayed an increased migration of the worms towards pristine and ssDNA functionalized SWCNT in comparison to ultrapure water as control. Additionally, paralytic movement was observed with SWCNT exposure in contrast to ssDNA-functionalized SWCNT-exposed animals. High doses of pristine SWCNT further displayed an increased expression of specific proteins obtained from the total protein extracts of the animals. Thus, the alteration in the navigation pattern of the worms, treated with pristine SWCNT, might be ascribed as a result of differentially expressed muscle proteins. Moreover, it is interesting to note that the modified SWCNT was effective in alleviating the atypical form of the inherent movements of the worm. Future investigation will further reveal the protein targets responsible for the altered navigation pattern of the worms.

Humidity sensors are of utmost importance in certain areas of life, in processing industries, in fabrication laboratories and in agriculture. Precise evaluation of humidity percentage in air is the need of various applications. Graphene and its composites have shown great potential in performing as humidity sensors owing to enormous surface area, very low electrical noise, high electrical conductivity, mechanical and thermal stability and high room temperature mobility. There is no such extensive review on graphene-based devices for humidity sensing applications. This review extensively discusses graphene-based devices intended towards sensing humidity, starting from the methods of synthesizing graphene, its electronic and mechanical properties favoring sensing behavior and different types of sensing mechanisms. The review also studies the performance and recent trends in humidity sensor based on graphene, graphene quantum dots, graphene oxide, reduced graphene oxide and various composite materials based on graphene such as graphene/polymer, graphene/metal oxide or graphene/metal. Discussions on the limitations and challenges of the graphene-based humidity sensors along with its future trends are made.

Recent advances in nanotechnology and nano biomaterials have attracted considerable attention in the field of cancer therapy. The development of biocompatible nanotherapeutics that selectively target cancer cells is a prime area of interest in current research. In the present study, graphene oxide nanosheets were synthesized using a modified Hummer’s method and characterized by using FTIR spectroscopy, Raman spectroscopy, and X-ray Diffraction analyses, FE-SEM, HR-TEM and AFM. FT-IR spectra revealed the presence of the characteristic wave-numbers of 1585 cm−1, 2841 cm−1, and 3443 cm−1 uncovering the presence of intrinsic functional groups predominantly C=C, C-O, and C=O bonds. The characteristic intrinsic defect proportions in the as-prepared GO sheets exhibited a portion of the ID/IG ratio of ~ 1.05, indicating thereby a lesser proportion of available defect quantity in our synthesized graphene oxide sheets. XRD studies uncovered an interesting characteristic value of (001) and (002) lattice planes at a diffraction angle of 30o, which indicated a crystalline nature of the as-prepared graphene sheets. Thermo Gravimetric analyses of the as-prepared sheets indicated that in the range of 300–900 ℃, the sheet exhibited a tremendous rate of thermal response at different applied temperatures, uncovering the underlying physico-chemical attributes of the sheets. It is observed from the DLS experimentation that GO sheets exhibited a zeta potential ζ-potential of − 9.3 mV, which is expected to be a most stable colloidal form. The lateral thickness of the graphene nanosheets was approximately 6.45 nm, which was corroborated by the TEM and AFM analyses, respectively. The potential biomedical application of graphene nanosheets was evaluated by assessing the cytotoxicity and antioxidant activity. The IC50 of H2O2 scavenging activity by GO sheets was determined to be 61.91 ± 1.14 µg/ml. The DPPH and H2O2 scavenging activity of the GO sheets increases with the increase with the dosage concentrations from 25 to 400 µg/ml, respectively. The in-vitro tests revealed that the GO sheets had a high level of cytotoxicity to the human breast cancer MDA-MB-231 cells that was concentration dependent. In contrast, the cytotoxicity of the GO sheets against the HaCaT normal cell line was marginal, suggesting that the graphene nanosheets could be safely used in cancer therapy.

In this study, electronic properties of Manganese atom doped Graphene are studied using Atomistix Tool Kit-Virtual NanoLab (ATK-VNL), QuantumWise simulation package. All the calculations are done using density functional theory. The doping of Manganese atom creates a small band gap and this gap increases with increasing doping concentrations. Chemical potential measurements exhibit a rise in the values for pristine Graphene is − 10.48 to − 9.91 eV for single doped atom to − 9.87 eV for double doped Manganese atom to − 9.57 eV for triple atom doped Manganese. Total energy calculated for pristine, one, two and three Manganese atom doped Graphenes are as − 4506.6, − 4599.5, − 4691.97 and − 4789.31 eV, respectively. Optical spectrum plots also support the aforementioned characteristics deviation in the pristine Graphene. Transmission spectrum is also varied for pristine Graphene in comparison to one, two and three Manganese atom doped nanosheets. Density of states calculations also illustrates the rise in the values for the number of states occupied by electrons for pristine Graphene, one to three Manganese atom doped nanosheet, respectively. The flow of current reduces with increasing number of impure atoms. Understanding the effect of Manganese as dopant at different lattice sites of 2D-Graphene helps in designing conductivity tunable Graphene based electro-mechanical devices and sensors for myriad nanoelectronic applications.

Two different morphological forms of graphene nanosheets: improved reduced graphene oxide (IRGO) and modified reduced GO (rGO) (MRGO) have been synthesised by improved and modified methods, respectively. Physical characterisations of these graphene nanosheets were carried out using X‐ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Colloidal stability of these nanosheets toward a selected bacterium (e.g. Staphylococcus aureus) was ascertained by zeta potential. In the present study, the authors for the first time made an attempt to study and compare the potentialities of these two different forms of graphene nanosheets as efficient bactericidal agents. Field‐emission scanning electron microscopy and TEM with energy dispersive X‐ray spectroscopy (EDAX) studies of IRGO and MRGO have been carried out to explore their underlying mechanism of antibacterial responses through physical as well as chemical interactions with the selected bacterial species.

Graphene has been conjugated with Silicene which is a 2D nanosheet of silicon crystal to analyze myriad physico-chemical properties. Upon intercalation of silicene between two graphene nanosheets, there has been a significant shift in the energy of electronic configuration at different isovalues from − 0.12 to + 0.12. Similarly, by analyzing the electronic energy states of silicene–graphene–silicene, a range of isovalues from − 0.08 to + 0.08 were observed. I–V curve exhibited a linear response for graphene–silicene–graphene sandwiched structure and a semiconducting like behavior for silicene–graphene–silicene structure. Band gap measurement in case of graphene–silicene–graphene system is reported to be ~ 0.18 eV, which is a narrow region. While in case of silicene–graphene–silicene, a band gap value of ~ 1.01 eV is calculated that appears to be a pretty broad region. Transmission spectrum also shows intensity in peaks for Gr–Si–Gr case as compared to Si–Gr–Si combinations. Silicon is widely perceived to exhibit outstanding semiconducting behavior and has already been used in devising various electronic devices. In this present work, we try to analyze the outcome of the silicene and graphene at the nanometer scale in various combinations in a bid to understand the potential interaction mechanism between the two nanosheets which would help in the fabrication of the silicene–graphene based optoelectronic devices.

Pristine metallic single-walled carbon nanotubes (6, 0), surface engineered with pyrimidine type DNA nucleobases, thymine and cytosine respectively, are transformed into semimetal forms by band structure engineering of the nanotubes. The hybrid systems are designed using ATK–VNL simulation software. Band structure and zero bias transmission spectra analysis witness a very small overlap between the conduction and valence bands around the Fermi level. IV-characteristic curves also support the semimetallic nature of SWCNT–DNA nucleobase coupling. The altered electronic structure of SWCNT is achieved due to strong chemisorption imparted by hydrogenation of DNA nucleobases which induce partial sp3 hybridization in the nanotube structure. Metal to semimetal conversion results in conductivity modulation in SWCNT and it has several applications in various fields like nano-electronics including NEMS design.

Multi-walled carbon-nanotubes are considered as promising drug-delivery tool for their unique physicochemical properties. The aim of our study is to assess the biological impact of pristine MWCNT in an in vivo model using Caenorhabditis elegans since it shares 60-80% homologous genes with human genome. The toxicity of MWCNT was determined by evaluating survival assay and motility of C. elegans . Gradual increase in the concentration of pristine MWCNT imparted adverse effects on survival potential and motility of C. elegans gradually. Death rate of worms increased from 7%-17% after 24 hours and from14%-23% after 48 hours with increasing concentrations of MWCNT treatment.

Graphene has been realized for its significant physico-chemical properties. The extraordinary surface area and high electronical conductivity of graphene makes it a potential candidate in the field of nanoelectronics and sensors. In this study, graphene has been conjugated with silicon and its different physical and chemical properties were evaluated. The total energy of the composite system came out to be −6111.62 eV. Chemical potential of the composite system exhibits ∼ 5.64 eV. DOS calculations for composite of silicon and graphene came out to be ∼ 17 eV−1 for the applied bias voltage of 40 eV, as when compared to higher values of DOS for monolayer silicon and graphene nanosheets. Silicon is widely known to exhibit semiconducting behavior and has already been used in fabricating various CMOS devices. In this present work, we try to study the outcome of the conjugation of graphene nanosheets with silicon nanosheets in different combinations. Understanding the interactions between two semiconducting materials could shed some light in the underlying physical and chemical interaction which would help in devising novel optoelectronic systems.

Elastic properties of a material dictate how much it will compress under extrinsic stress and determine the net stiffness of a material. In the present study, employing molecular dynamics simulation, calculation of the Young's modulus and its relation with elasticity of the material has been performed at different temperature ranges varying from 4oC (277 K) to 2227oC (2500 K). Metallic SWCNT (5, 5) and semiconductor SWCNT (7, 0) are selected as our experimental material. Gradual increase in temperature reduces rigidity and as well as decreases elasticity of the pristine nanotubes as evident from the gradual decrease in the Young's modulus value. But Stone-Wales defect induced SWCNT retains the rigidity of the nanotubes even at higher temperature as evident from higher Young's modulus value. Understanding the stress-strain relation at different temperature ranges for SWCNT would help us in exploring its mechanical properties and in turn designing devices of ultra-high stiffness at higher temperature, finding its applications from aerospace to medical diagnostics.