Graphene and its derivatives show great potential for biosensing due to their extraordinary optical, electrical and physical properties. In particular, graphene and its derivatives have excellent optical properties such as broadband and tunable absorption, fluorescence bursts, and strong polarization-related effects. Optical biosensors based on graphene and its derivatives make nondestructive detection of biomolecules possible. The focus of this paper is to review the preparation of graphene and its derivatives, as well as recent advances in optical biosensors based on graphene and its derivatives. The working principle of face plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS), fluorescence resonance energy transfer (FRET) and colorimetric sensors are summarized, and the advantages and disadvantages of graphene and its derivatives applicable to various types of sensors are analyzed, and the methods of surface functionalization of graphene and its derivatives are introduced; these optical biosensors can be used for the detection of a range of biomolecules such as single cells, cellular secretions, proteins, nucleic acids, and antigen-antibodies; these new high-performance optical sensors are capable of detecting changes in surface structure and biomolecular interactions with the advantages of ultra-fast detection, high sensitivity, label-free, specific recognition, and the ability to respond in real-time. Problems in the current stage of application are discussed, as well as future prospects for graphene and its biosensors. Achieving the applicability, reusability and low cost of novel optical biosensors for a variety of complex environments and achieving scale-up production, which still faces serious challenges. Since the isolation of graphene in 2004, two-dimensional (2D) layered materials have attracted great attention . CompareOptical biosensors offer significant advantages over traditional analytical sensing technologies, enabling direct, real-time and label-free detection of biological and chemical substances. Along with the advances in emerging science and technology, a variety of cross-disciplinary and advanced approaches  are applied to novel optical biosensors. Optical detection is achieved by using the interaction between the optical field and the biometric element. There are two main modes of optical biosensing: label-free mode and label-based mode. In the label-free mode, biosensing is achieved based on signals generated directly from the interaction of the analytic material with the transducer. Label-based mode sensing achieves biosensing by using a label and then generating an optical signal using methods such as colorimetry, fluorimetry, or luminescence. Biomolecular detection is widely used in food safety, environmental monitoring, disease prevention and clinical treatment . In partIn the past decade, biosensing applications based on two-dimensional materials have developed rapidly ,16. In tThe preparation method of 2D materials plays an important role in whether they are suitable for biosensors, biomolecular detection and biomedical therapy. Graphene and its derivatives mainly include four forms, which are graphene itself, GO, rGO and GQDs. In this section, we focus on the synthesis of these 2D nanomaterials.2 hybridized carbon atoms . T. T2 V−1 n plasma b 63]. W. W2 V−1 n plasma c 64]..2 V−1 S−3) and potassium chlorate (KClO3) to form graphite oxide . . 109]. HThe bottom-up approach is to assemble GQDs from molecular precursors, and the diversity of carbon precursors determines the size and performance of the synthesized GQDs. Among the bottom-up methods, cage opening of fullerenes methods, stepwise organic methods and microwave-assisted methods are commonly used.Loh et al. reported an open-cage synthesis of GQDs by metal-catalyzed fullerenes; they used fullerene as the reactant, and through the strong interaction between carbon atoms of fullerene on the ruthenium surface, vacancies appeared on ruthenium surface, which contributed to the embedment of fullerene molecules, carbon clusters occurred at high temperature, and GQDs with different shapes were formed through diffusion and aggregation . Chua etStepwise organic synthesis is the synthesis of GQDs from small carbon precursors by organic reactions, and the structure of the synthesized product can be controlled. Yan et al. prepared GQDs by stepwise organic synthesis, and their quantum dots were composed of 168, 132 and 137 conjugated carbons formed by the oxidation of polystyrene dendritic precursors. The synthesized GQDs are very stable, and the method can control the properties of the synthesized GQDs according to the requirements a 113,11. Tian etHydrothermal synthesis of GQDs is time-consuming and not suitable for large-scale industrial production. The method of microwave-assisted synthesis of GQDs can accelerate the synthesis speed, heat evenly, and the size distribution of precursor is uniform. The main advantage is that GQDs can be synthesized without any passivating agent. Using aspartic acid and ammonium bicarbonate as raw materials, Zhang et al. prepared blue luminescent GQDs by microwave-assisted synthesis at 560 W working power b 116]. . 116]. ZIn this section, we summarize and discuss the common methods for the preparation of graphene and its derivatives and analyze the advantages and disadvantages of each method. We can decide the method to prepare the samples based on the desired target properties and the advantages and disadvantages of various preparation methods, and present them in The methods for functionalizing graphene-based nanomaterials with biomolecules can be divided into two categories, non-covalent modification and covalent functionalization, according to the principle of interaction. Both methods have their advantages and disadvantages. For example, non-covalent crosslinking does not affect the intrinsic properties and structure of nanomaterials, nor does it affect the activity of biomolecules . The preUsually, the simplest and fastest way to prepare biomolecule-functionalized graphene and its derivative complexes is the direct physical adsorption of biomolecules on the surface of graphene and its derivative materials without the aid of external conditions. The electrostatic, π-π stacking, hydrogen bonding and hydrophobic forces between biomolecules and graphene and its derivative materials play an important role in facilitating their interactions. Due to the large two-dimensional aromatic surface, graphene materials can be tightly bound to molecules containing aromatic rings by π-π superposition . TherefoGiven the high stability of covalent bonding, covalent modification methods are of great importance for functionalized graphene nanomaterials of biomolecules. Since the surfaces of GO and rGO contain oxygen-containing functional groups such as carboxyl and hydroxyl groups, they can effectively immobilize biomolecules containing a variety of functional groups . Most biOptical biosensors have high sensitivity and can even detect single molecules. Currently commonly used optical biosensors are mainly based on the following methods, surface plasmon resonance (SPR), surface-enhanced Raman spectroscopy (SERS), fluorescence resonance energy transfer (FRET) and colorimetric  133]. S. S133]. The process when a donor fluorophore in the excited state non-radiatively transfers its own energy to a neighboring acceptor fluorophore so that the acceptor emits fluorescence at its characteristic wavelength is known as FRET. The spectral overlap, distance and relative orientation between the donor and the receptor all affect the efficiency of FRET. The distance and relative orientation between the donor and receptor are particularly important for the construction of highly sensitive FRET biosensors . The FRES. aureus-specific gene sequence detection based on GQDs and gold nanoparticle (AuNPs) pairs  by binding to GO by Zhu et al.  pairs a 145]; ; S. aureu et al. c 147]. . S. aurecreening d 151]. . S. aure13–1015 times . . 3O4 nanAmong optical biosensors, colorimetric biosensors are capable of producing signals visible to the naked eye that can be observed without the use of other tools. Colorimetric sensing is closely related to the materials used to make the sensors. Depending on the sensing material, the sensing mechanism of the colorimetric sensor varies . Colorim−1 [2O2 and cholesterol. The sensor exhibited good sensitivity and selectivity for cholesterol (LOD of 78 pM) and H2O2 (LOD of 6.88 μM) with high stability at different temperatures. The biocompatibility of the composite CuO:GNS is superior to that of CuO  of graphene and its derivatives . We introduce optical biosensors for biomolecule detection: FRET biosensors, SERS biosensors, SPR biosensors, colorimetric biosensors, and summarize the research progress of graphene and its derivatives in the field of sensing. Graphene and its derivatives are two-dimensional layered materials composed of spNovel optical biosensors and other applications using graphene and its derivatives as sensing elements have been developed, which can be used for the detection of a range of biomolecules such as single cells, cellular secretions, proteins, nucleic acids, and antigen-antibodies; these new high-performance optical sensors are capable of detecting changes in surface structure and biomolecular interactions with the advantages of ultra-fast detection, high sensitivity, label-free, specific recognition, and the ability to respond in real-time. However, the application areas of graphene and its derivatives-based biosensors are limited, and many applications are restricted to biomolecule detection, which needs to be extended to other medical fields. In addition, efforts should be made to achieve the applicability, reusability, and low cost of new biosensors to adapt to various complex environments, not limited to the laboratory, and to achieve scale-up production, which still faces serious challenges.(1)Understanding the interaction mechanism between biomolecules and graphene and its derivative materials. The analytical performance of optical biosensors based on graphene and its derivatives is linked to the number and arrangement of biomolecules on the surface of graphene and its derivative materials.(2)The homogeneity of graphene and its derivatives in terms of size, thickness, biocompatibility, and the number of surface functional groups is difficult to ensure; this inhomogeneity has a great impact on the performance evaluation and reproducibility of the constructed optical biosensors. Optimization of production methods and improved control of the size and morphology of the produced particles and standardization of the manufacturing process.(3)The type and functionalization of precursors during the preparation of graphene and its derivatives often introduce different impurities, and further research should be conducted to simplify effective sample preparation methods to avoid the interference of other substrates and to ensure that their biosensing performance as signal nanoprobes is not affected.(4)It is also a serious challenge to develop a biofunctionalization method that maintains high stability without changing the structure and function of biomolecules and graphene and its derivative materials, to develop biosensor devices with high stability and reproducibility, and to expand the practical applications of biosensors based on graphene and its derivative materials.(5)Emphasis should be placed on miniaturization, standardization, and multiple readouts of biosensors to reduce the incidence of false negative/positive results. Further miniaturization, integration with fluidic systems, and integration of multi-chip systems are important challenges for the next generation of graphene and its derivatives optical biosensors.(6)The combination of graphene and its derivative optical biosensors with smartphones, in particular, has great potential to enable low-cost, reliable and versatile biosensing platforms that can be widely used in the field and provide excellent convenience for on-site detection of pathogens in remote areas.


We find that the fullerene’s VDOS smoothly converges to the graphene characteristic line-shape, with the only noticeable discrepancy in the frequency range of the out-of-plane optic (ZO) phonon band. From a comparison of both systems we obtain as main results that: (1) The pentagonal faces in the fullerenes impede the existence of the analog of the high frequency graphene’s ZO phonons, (2) which in the context of phonons could be interpreted as a compression (by 43%) of the ZO phonon band by decreasing its maximum allowed radial-optic vibration frequency. And 3) as a result, the deviation of fullerene’s VDOS relative to graphene may hold important thermodynamical implications, such as larger heat capacities compared to graphene at room-temperature. These results provide insights that can be extrapolated to other nanostructures containing pentagonal rings or pentagonal defects.The study of nanostructures’ vibrational properties is at the core of nanoscience research. They are known to represent a fingerprint of the system as well as to hint the underlying nature of chemical bonds. In this work, we focus on addressing how the vibrational density of states (VDOS) of the carbon fullerene family (C The vibrational properties of fullerenes are incompletely understood, particularly with respect to the effect of molecular size. Here the vibrational density of states of fullerenes is shown by density functional theory to converge smoothly to that of graphene, hindered only by the presence of frequency compressed radial optic vibrations due to the pentagonal faces in the fullerene family. As a consequence of the very interesting properties shown by carbon-based nanomaterials, such as mechanical, electronic, optical, and chemical ones, a great number of fundamental investigations and technological applications have been developed since7. Despite the plethora of research done on carbon nanomaterials like fullerenes, nanotubes, nanoflakes, etc.16, still, some physicochemical properties have not been fully investigated. In particular, insufficient attention has been paid to the vibrational properties of fullerenes, and how they depend on their size evolution and morphology.Since the discovery of the C19. This is not only due to their relevance in the design of nanodevices20 but also because of a notorious development of vibrational spectroscopies, opening the opportunity to directly compare experimental measurements and theoretical calculations21. For example, exploiting the symmetry breaking in supported metal nanoparticles (NPs), Carles’ group developed a technique to directly measure the vibrational density of states (VDOS)23. Such a breakthrough24 lead to the understanding of intricate experimental results using well-established theoretical results29, which link the VDOS as an NP vibrational fingerprint that correlates to the morphology of the system21. Contrasting these results, organic macro-molecules spectroscopy relies only on Raman and IR spectroscopy to experimentally study them. Hence, given the nature of these experimental measurements, we have access to only a selection of vibrational modes and not to their full VDOS.During the last couple of decades, the vibrational properties of metal nanostructures have gained a lot of attention30, the evolution of thermodynamical properties on metallic nanoparticles33, the formation of surface plasmons in sodium nanoclusters34, as well as the convergence of molecular vibrational spectra to a bulk-like phonon density of states in metal NPs35. In the particular case of metal NPs, a smooth transition of the VDOS from the nanoscale to the bulk has been reported, the study that is missing in the case of carbon nanostructures.A fundamental question in nanoscience is how the transition from molecular  properties evolve to bulk behavior as a function of the system size. In this regard, several results have been published such as the birth of the localized surface plasmon resonance in Au nanoclustersIn this work, we present a theoretical investigation of the vibrational properties of fullerenes and their dependence on size (20 → 720 atoms) at the density functional theory (DFT) theory level. In particular, we analyze the evolution of the fullerene VDOS toward the bulk material (graphene) regime. Analysis that leads to an interesting and counterintuitive difference between the vibrational modes in fullerenes and the phonon bands in graphene: a severe restriction on the out-of-plane  optical band (ZO-modes) in fullerenes in the neighborhood of the Γ symmetric point. These results show that the presence of the pentagonal faces in the fullerene family hinders the smooth convergence of their VDOS to the bulk graphene one. Furthermore, these findings hint that pentagonal impurities in graphene can have far more important implications on its vibrational properties than expected.Ih symmetry. As a consequence of the finite size of the fullerenes, the frequency spectrum is discrete, and it has a finite acoustic gapνAG . The vibrational spectrum extends from νAG up to ~1600 cm−1, although in the case of C20, it is notorious a smaller frequency distribution range which goes from ~480 cm−1 to 1340 cm−1. It is well known that the C20 fullerene is a controversial molecule, in which the reported calculated structure strongly depends on the utilized level of theory due to its high electron correlation and multiconfiguration character42. Often, different methodologies differ in the molecular point group of the cage ground state of C20, which is reflected on the values of the interatomic forces and consequently in its vibrational spectrum. In particular, the main differences are located near the lowest frequency region. In previous theoretical work, Saito and Miyamoto36 reported a frequency distribution range that goes from ~115 to ~1435 cm−1 using DFT with the hybrid functional B3PW91. Another study by Schütt et al. recently reported a vibrational spectrum ranging from ~100 to ~1400 cm−1 using a machine learning method based on deep neural networks, SchNet42, trained on DFT(PBE + vdWTS)43 level of theory. Similar results can be obtained with other machine learning approaches46. In these two works, the νAG is lower than in our case because the lower symmetry group considered as a global minimum, Dh3 instead of Ih. In the case of the highest frequency, also known as cut-off frequency νCOF, the lower value displayed in C20 compared to other fullerenes is attributed to the nature of the carbon–carbon bond in C20 coming from the fact that the geometrical structure is only formed by pentagonal faces. The rest of the studied fullerenes are more electronically stable and different levels of theories give consistent results, showing a smoother transition between different sizes.Figure ∞, where the twelve pentagonal faces are completely diluted. From intermediate sizes, such as the C240, we can see that the line shape of the VDOS already has the main features of the biggest fullerene in our study . Furthermore, the fullerenes display the higher intensity (main) peak in the VDOS around 670 cm−1, a characteristic feature that emerges from the 60 atom structure.Based on the fact that fullerenes are single-layer carbon cage structures, it is natural to assume that in the limit of large fullerene diameters, the VDOS should converge to the graphene’s VDOS given its single layer character. To explore this hypothesis, in Fig. 720 fullerene presents most of the features displayed by bulk graphene, with the obvious difference of the finite acoustic gap. However, it is worth highlighting the mismatch located in the range of ~540–910 cm−1, where the graphene peak around ~850 cm−1 is missing in the fullerene family  and optic (ZO) vibrations, and that their respective frequency intervals are  and  cm−149. These two bands are highlighted in Fig. ZA and VDOSZO, respectively  ~ νn with n > 2 at the lower part of the spectrum. Now, in the case of fullerenes, we can see different behavior from Fig. 720’s VDOS recovers most of the features from the graphene case with the difference of a late start of the VDOS due to the acoustic gap and the already discussed compressed ZO band peak around 670 cm−1. An analysis of Fig. 35. To quantify such effects, we analyze the thermodynamics of both systems, C720, and graphene, to elucidate their relative behavior.Before going to our particular case, we should summarize some equivalent results from metallic NPs. It is a well-established result that metal NP has a larger heat capacity compared to their bulk counterpart for a short interval at low temperatures, e.g., ~3–40 K in the case of Au NPg(ν) is the VDOS function, kB is the Boltzmann’s constant, and the weight function f comes from the temperature derivative of the Bose–Einstein distribution function,In general, thermodynamical variables are obtained by a cumulative process of the vibrational properties of the system, meaning that computing such quantities involve a sum or an integral over the vibrational spectrum weighted by a function. As an example, let’s consider the specific heat,Now, by using Eq.  we can qentclass1pt{minimaThese results demonstrate that indeed the excess of vibrational modes created in the ZO band by the pentagonal faces in fullerenes see Fig.  have an 21, in the present case, there will not be a full convergence to the graphene VDOS since the pentagonal facets are required to close the cage structures of fullerenes. In particular, in terms of the phononic bands in graphene, the ZO-equivalent normal mode oscillations are greatly affected by the presence of pentagonal facets, which sets a lower frequency (~750 cm−1) and dynamically different ZO cut-off eigenstate  and the pseudopotential for carbon with 4 valence electrons corresponding to ECP2SDF were used54, as implemented in the TURBOMOLE code55. To guarantee accurate frequencies’ calculation, the structures were optimized with a force tolerance of 10−6 Hartree Bohr−1. The computed harmonic frequencies were validated with reported calculations for carbon dimer’s bond length, binding energy, and vibrational frequency62. In addition, the whole vibrational spectrum of C60 fullerene was calculated and compared with experimental results63 for validation. The VDOS was constructed using a Gaussian broadening with a width of 20 cm−1 of the 3N − 6 frequencies.All computations were done at the density functional theory (DFT) level within the generalized gradient approximation (GGA), using the Perdew-Burke-Ernzerhof (PBE) parameterizationx is a radial vector and {vi} is the set of eigenvectors. Then, the in-plane  contribution is computed via XY-VDOS = VDOS–Z-VDOS.The selection of purely radial vibrational modes in fullerenes and their contribution to the VDOS was estimated by performing a radial projection of the whole vibrational spectrum, Peer Review FileSupplementary Information


For field-like environmentalgas monitoring and noninvasive illnessdiagnostics, effective sensing materials with exceptional sensingcapabilities of sensitive, quick detection of volatile organic compounds(VOCs) are required. Carbon-based nanomaterials (CNMs), like CNTs,graphene, carbon dots (Cdots), and others, have recently drawn a lotof interest for their future application as an elevated-performancesensor for the detection of VOCs. CNMs have a greater potential fordeveloping selective sensors that target VOCs due to their tunablechemical and surface properties. Additionally, the mechanical versatilityof CNMs enables the development of novel gas sensors and places themahead of other sensing materials for wearable applications. An overviewof the latest advancements in the study of CNM-based sensors is givenin this comprehensive organized review. They are presentin a variety of products. Due to higher volatility, mobility, andresistance to degradation, VOCs can travel over large distances inthe atmosphere.2  is one of the most prominent analytical techniques for identifyingVOCs.19 Carbon-basednanomaterials (CNMs) are appealing prospects for the future of automatedsensor technology because of their excellent sensing detectabilityand intriguing transduction capabilities. A majority of atoms in 0–2-dimensionalCNMs are exposed to the outside environment due to their huge specificsurface area and remarkable sensitivity.22 Low-dimensionalCNMs like CNTs, graphene, and MXene have a large specific surfacearea to reach a high detection sensitivity for VOCs; however, themajority of their atoms are discharged into the air.24 We focused on the most recent developments in CNMs for VOC sensingin this comprehensive review.Nowadays, carbon-based nanomaterials are encouraging the scientificcommunity to make powerful sensor devices due to their characteristicstructure, especially graphene and its derivatives such as grapheneoxide (GO), CNTs, reduced graphene oxide (rGO), Cdots, and MXene.Several ways of interacting with VOCs, such as π–πstacking, electrostatic forces, and noncovalent bonding, make themsuitable candidates for adsorbents.226 The CNT, which is a circular tube-like structuredue to its rolled up graphene sheets, can be a single-walled or multi-walledCNT. Hence, it is considered a 1D carbon material; its length canbe extended to some micrometers long, whereas its diameter can befound to be in the nm range.28 Carbon dots (CDs) aregaining much more attention because of their biocompatibility, excellentphysicochemistry, and tunable photoluminescence and are being exploredas biosensors.30 They are a new type of carbonnanostructure of >10 nm size and the most water-soluble carbonmaterial.31 The effective visualizationof their shape andsize can be studied by a TEM image, which has been shown in The carbon nanomaterials can be synthesizedwith controlled shapeand size from 0D to 2D, whereas 3D carbon materials are consideredas graphite, diamond, etc. Except for graphite and diamond, we havefocused on graphene, CNTs, CDs, and other carbon-based nanomaterials.When we talk about nanomaterials, their shapes and sizes are morecritical because of surface catalytic reactions. The reduced graphene(rGO) obtained by heating or using a reducing agent on GO sheets isnot spherical. Its nominal effective diameter can be calculated insteadof the actual size using dynamic light-scattering (DLS) techniques.Through this technique, different scientists measured the averagesizes of rGO sheet combinations of honeycomb structures of a carbonatom, which were found to be 2.93 μm, 0.5–5 μm,etc.35 This degree of oxidationis responsible for the electrical conductivity of modified grapheneand the degree of oxidation depending on various synthetic routes.The carbon atoms of modified oxidized graphene are partially sp3 hybridized and can move above and below the plane.36 Another derivative of graphene-like sheets canbe obtained by reducing graphene oxide through chemical reductionor simple heating methods. Park and Ruoff examined the elemental analysisof carbon and oxygen atoms  for rGOmade by combustion techniques and discovered that rGO is not the sameas pure graphene since it contains a considerable quantity of oxygen.Furthermore, when cooled to lower temperatures, its conductivity reducesby 3 orders of magnitude, causing it to display nonmetallic behavior.37 In this way, a very clear difference can beseen between pristine graphene and graphene derivatives such as GOand rGO. Both pristine graphene and its derivatives are two-dimensionalstructures. Still, pristine graphene is relatively inefficient forthe adsorption of VOC molecules. In contrast, its derivatives havemore adsorption sites due to the presence of different oxygen groupsand hence offer high sensitivity toward VOC molecules of the film.38 On the other hand, the current–voltage(I–V) characteristics forboth GO and rGO exhibit ohmic contact, which is suitable for gas-sensingapplications.39The other derivatives or oxidizedforms of graphene by oxygen functionalgroups such as carboxyl (−C=O), epoxy (−C–O–C−),and hydroxyl (−OH) make graphene oxide suspended in water andother polar media.32-hybridized atomic orbitals, and as a result, reduced grapheneoxide (rGO) became a conductive active material for molecular sensors.The rolling form of the graphene sheet results in π confinement due to σ–π rehybridizationat its circular curvature structure and creates an asymmetric distributionof σ-bonds and π-orbitals on both sides (inside and outside)of the nanotube, forming a high π-electron conjugation outsidethe nanotube.40 Thus, the surface of CNTscan donate or withdraw electrons from any electron-donating or electron-withdrawingentity during molecular interaction, thereby modulating overall electricalresistance.42 Several groups have approachedthe molecular orbital (MO) theory for the electronic structure ofCQDs, which demonstrated that transitions have occurred in n →π* and π → π* as available transition energies.45 According to Larson and Hu, the aromatic sp2-hybridizedcarbons are responsible for their π-states. The presence ofπ-electron conjugation results in high charge transfer in carbon-basedmaterials.46 Generally, the detection ofVOCs is governed by their interaction with carbon-based materialsby diffusion and sensed by the active center of carbon-based materials,50 microgravimetric sensors,55 and resistive sensors.59 When a molecule species interacts with the sidewallsof carbon-based or any semiconductor materials during gas detection,changes in conductance61 (due to charge transfer or mobilitychange) or capacitance62 (from inherentor induced dipole moments) occur.65 The interaction betweenthe VOCs and carbon-based compounds  depends stronglyon the architecture and design of the composites or materials whichmay have a larger contact area, thus allowing greater sensitivity.The CNT has two variables, SWCNT and MWCNT. Depending upon chirality,SWCNTs can be semiconducting or metallic,67 and MWCNTs have only a metallic character and are therefore unsuitablefor fabricating gas transistors.It is very much essential to note the originof electrical conductivityproperties of graphene, CNTs, and Cdots for sensing properties. Itwill help the understanding of surface interaction as a chemisorptionreaction which changes the electrical properties of carbon-based materials.The 2D graphene sheet shows high carrier mobility due to planar sp470 Meanwhile,research into the construction of sophisticated sensors for VOC detectionis expanding rapidly .72 A thorough explanation of the VOC-detecting device’s sensingprocess is initially required to construct a powerful VOC sensor.Recently, point-of-care applications, various diseasediagnoses,atmospheric gas tracking, and other fields have significantly increasedthe demand for accurate VOC gas analysis.75 research toward sensing technologies. These materials have beenshown to be more effective in producing higher VOC sensors.78 Three steps commonly take place in gas sensors manufactured usingCNMs for VOC detection: (i) trapping of VOC gas, (ii) their interactionwith the sensing active site, and (iii) dispersing of the VOC gas.Focusing on the complex interactions between the VOC gas and the activecenter that detects them, CNMs have been used to create a range ofVOC gas sensors, including optical81 and microgravimetric ones.86 Regarding optical sensors, spectrometric or colorimetric variationsin the sensing materials are brought on by the intermolecular interactionsamong VOC samples and the active center81 and resistance-based sensors.90Research on developing gas sensors has primarily focused on nanoparticlesbecause of their superior physicochemical characteristics and highsurface-to-volume ratio. The recent discovery of CNMs has prompted591Due to the considerable electrochemical, mechanical,optical, andthermal properties of CNMs, many research studies have been done inthis area during the last three decades. Fullerenes, carbon nanotubes,graphene, carbon dots, carbon nanohorns, and carbon black are examplesof zero-, one-, two-, and three-dimensional CNMs that have shown suchinherent properties that can be easily modified in the developmentof cutting-edge innovation for sensing applications. Nanomaterialshave opened up new pathways and options for sensing analysts or targetmolecules.93Carbon-based nanostructureshave several benefits over other commonlyused sensor materials, including simple manufacturing procedures,unexpected physiochemical characteristics, greater sensing properties,environmentally friendly materials, improved detection accuracy, highflexibility, sensitivity, and reliability. They also have a largesurface-to-volume ratio, high stability, high electrical conductivity,biocompatibility, reduced size, and an improved surface area. CNMsare being studied as a result of further utilization of efficientsensor technology.94 The many CNM-based sensorsutilized for VOC detection are listed in Carbon nanostructures likeCNTs and graphene can be used to detectextremely small levels of danger and greenhouse gases. Therefore,using the CNM-based sensor to develop susceptible, small energy gassensors is both of significant academic interest and of enormous economicsignificance.62 carbon atoms organized in cylindricaltubes with diameters ranging from 1 to 100 nm. Single-wall carbonnanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) are thetwo types of CNTs used most commonly. MWCNTs, on the other hand, arecomposed of multiple sheets of concentric single-walled graphene cylinderswith an interlayer spacing of 3.4 and are held together by van derWaals forces.111 SWCNTs are the rolledform of the graphene sheet. Hexagonal rings make up CNTs and controltheir size, curvature, and electronic properties. Chirality refersto the configuration of carbon hexagonal rings in nanotubes.112A one-dimensional carbon allotrope known as a carbonnanotube (CNT)is composed of sp113 CVD,114 and laser ablation115 are common techniques for making CNTs. The CVD process and the dischargemethod are more advantageous for the mass production of high-qualityCNTs.114Since 20 years, CNTs have been made ona massive scale for numeroususes. Arc discharge,116 A quick, painless, inexpensive, noninvasivemethod for early disease detection and ongoing physiological monitoringis breathing analysis.118 Analyzing the diaphragmaticmovement when breathing can help detect human disorders like atypicalsleep problems, asthma, heart attack, and lung cancer early on.120 Due to their appealing qualities, such as good biocompatibility,wearing comfort, low cost, as well as sensitivity to breathing activitiesin the aspect of lower frequencies and slight amplitude body motions,triboelectric nanogenerators (TENG) have recently been widely usedfor self-powered respiration monitoring. TENG-based respiration sensorscan accurately and continuously track physiological respiratory behaviorsand exhaled chemical regents for individualized health care.121 Further, the 'Liu' research groupdesigneda respiration-driven triboelectric sensor (RTS) for concurrent biomechanicaland biochemical breath measurement that can directly transform breathflow into electricity.122 The Wang researchgroup also created an integrated triboelectric self-powered respirationsensor (TSRS) to track both human breathing patterns and the amountof NH3 in exhaled gases.123One of the oldest clinicalpractices is breathing analysis usedfor medical purposes. The binding of volatile compounds to a sensorarray, the creation of sensor modifications, which produce distinctivepatterns of signals, and the integration of signal patterns allowingcategorization are the main phases in the breathing analysis workingprinciple, which also is based on the human olfactory system.3 in exhaled gases. 124 Su et al. created an alveolus-inspired membranesensor (AIMS) for self-powered wearable nitrogen dioxide detectionand personal physiological evaluation in 2020. This sensor may beused to detect human breath activities for breath analysis.125'Su' and his research team created a triboelectric self-poweredrespiration sensor (TSRS) in 2019 to monitor human breathing patternsand the amount of NH2S below breathing concentrationlevels in humid airflow (sc-SWCNTs). The repeatable sensor constructionmethod is based on controlled multiplexing dielectrophoretic sc-SWCNTdeposition. The sensing region is developed and produces gold nanoparticlesthat solve detection at room temperature by leveraging the affinityof gold and sulfur atoms in the gas. The estimated limit of detection(LOD) for sensing devices functionalized with optimum nanoparticledispersion is 3 ppb, and their sensitivity is 0.122%/ppb. Our sensorssurpass certain electrochemical sensors that seem to be availableon the market in terms of improved stability and response levels despiteself-validation.126Using a self-validating 64-channel sensor array based on semiconductingsingle-walled carbon nanotubes, the Panes–Ruiz research groupshowed precise detection of Hn-pentane.Except for isopropanol, the SDBS-CNT sensors could detect water, acetone,chloroform, and ethanol but not many biomarkers. N-Pentane, acetone, isoprene, and ethanol were all reactive substancesfor the BnzlkCl-CNT sensors. Although it was shown that pristine CNTsresponded best to the majority of the aromatic VOCs in the collection,CTAB-CNT sensors were just moderately sensitive to most VOCs and lackedsignificant selectivity.127According tothe kind and concentration of various surfactants,Chatterjee et al. investigated how several lung cancer VOCs foundin human breath impacted the selectivity and sensitivity using CNT-basedsensors . The performance of thesensors is found to be affected by both the interaction of the surfactantwith the analyts and the supramolecular assembly with CNTs. Surfactant–CNTsensors were produced using the spray LbL approach. Water and otherpolar VOCs, particularly methanol and other alcohols, have demonstratedgood sensitivity to CNT-DOC sensors. TX405-CNT sensors were sensitiveto three chemicals: benzene, chloroform, and 128 The total sensor system also benefits from this drop injunction potential. 129Moreover,'Sinha' research group used zinc oxide (ZnO) and CNTsto create a composite-based chemiresistive sensor. A mechanism hasbeen linked to the VOC adsorption process’s temperature- andmaterial-dependent switching. Due to their simplicity in low-temperaturesynthesis and the large variety of VOC sensing, stability, or otheradvantageous qualities, ZnO/CNT composites have been selected in thiswork as a crucial material above other metal oxides. Additionally,it is anticipated that a p–n heterojunction will develop atevery point in which CNT and ZnO are in contact. This will also impactthe composite sensor’s ability to sense. A potential is createdas an outcome of the interaction of n-type (ZnO) and p-type (CNT)materials. As a result, if VOCs were adsorbed onto the surface ofa composite sensor, their potential should decrease.For the purpose of detecting volatileVOCs, the Turner researchgroup developed vapor quantum resistive sensors (vQRSs) utilizingrandom networks made of carbon nanotubes (CNTs) that have been functionalizedwith caffeine. Energy-dispersive X-ray spectroscopy (EDS) and a localizedtransmission electron microscopy (TEM) image both demonstrate thatcaffeine has moved to the CNT–CNT junction (CNTj). Furthermore,at the CNT intersection, we conducted localized EDS 5a,b. Acc130Specific VOCs like acetone, toluene,and ethanol have increasedsensitivity and distinct selectivity and a quick response time withcaffeine-enhanced CNT junction (Caf-CNTj) vQRSs. According to moleculardynamics simulations, the sensor’s sensitivity is diffusion-limited,with ethanol actively contributing (MD). The created Caf-CNTj sensorscould be a strong contender for various activities performed by anelectronic nose, including breath analysis and food quality monitoring.131Bohli et al. created a room-temperaturetoluene and benzene sensorin 2019 using MWCNTs functionalized with a long-chain thiol self-assembledmonolayer, 1-hexadecanethiol (HDT), and decorated with Au nanoparticles.The thiol monolayer adhering to the MWCNTs was examined using FT-IRand high-resolution TEM, which were used to describe the gold nanoparticledecorating. The ability of Au-MWCNT and HDT/Au-MWCNT sensors to detectVOCs at levels as low as ppm is evidence that the self-assembled layerenhances the sensing selectivity, sensitivity by a factor of 17, andresponse dynamics. The response of the Au-MWCNT sensor to variousvapor injection amounts for toluene and benzene at room temperatureis shown in 4 microflowers (MFs) were used toembellish MWCNTsin composites for the detection of NH3. The material’sporous nature, the large specific surface area, and the p–nheterojunction formed by the MWNTs and NiWO4 contributeto the better sensing capabilities of this composite. The sensor basedon 10% (MWN10) has the best gas sensitivity, with a sensitivity of13.07 to 50 ppm of NH3 at room temperature and a detectinglower limit of 20 ppm, according to the gas sensitivity of the sensorbased on daisy-like NiWO4/MWCNTs.132NiWO7133 winningthem the Nobel Prize for their contribution to Physics in 2010.134 Pure graphene and graphene oxide (GO) are thefamily members of “graphene”. Graphene is a single layerof graphite formed of predictable hexagonal arrangements of 2D carbonatoms. This arrangement is identical to that of graphite. Grapheneis relatively light, weighing just around 0.77 mg per square meter.135Graphene has garnered a great deal of scientific attention sinceNovoselov and associates used mechanical exfoliation to synthesizeit for the first time in 2004,2 V1 s1), much more significant than carbon nanotubes (CNTs),is made possible by its zero band gap.136 It possesses exceptional mechanical strength, an extremely highsurface-to-volume ratio,138 high capacitance,140 outstanding thermal conductivity,141 exceptionalelectrical conductivity, and the possibility for atomically cleangraphene sheets on the graphene lattice.142 In addition to such amazing properties, graphene also enables sensitiveanalyte detection because of its exceptionally low electrical noise.143 Functionalized reduced graphene oxide (RGO)VOC sensors for detecting the ppm level of VOCs was developed by Tombelet al. . The three VOCs that werethe focus of the detection studies were acetone, toluene, and isoprene.These experiments were conducted at ambient temperatures of 30 °Cand 40% relative humidity.145Smart electronic material 'Graphene'has many unique propertiesand distinguishing characteristics. The structure’s extremelyhigh electron mobility  in various ratios. This nanocompositeis utilized as a sensor to detect NH3, and it performssubstantially superior to pure reduced graphene-oxide-based gas sensors,exhibiting an outstanding response (19.2%) to NH3 at ambienttemperature.147Reduced graphene oxide (rGO)/metalloporphyrin-basedVOC sensorsare simple and affordable to make and can precisely detect VOCs linkedto a number of diseases often present in human breath. They have beendescribed by the Lee research group. Using a drop casting technique,we created an rGO-metalloporphyrin-sensing array and examined it withEDS and scanning electron microscopy (SEM). Next, three disease-relatedbreath VOCs , as well as carbonmonoxide, were introduced to the detecting array.4 cm2/(V s), and low resistivity of4 × 10–1 cm, acetone molecules are more readilyabsorbed on the surface of rGO thin films. As a result of the rGOsensing material used in the QCM gas sensor, rapid reactions are possible.The QCM gas sensors’ quick reaction and recovery periods of20–30 s have been proven using commercially available rGO thinsensing films.148Gupta et al. investigatedthe use of thin coating rGO as a sensingmaterial on a QCM sensor to detect VOC vapors at ambient temperature.To make the rGO suspension, the aqueous suspension of GO paste isfirst reduced with ascorbic acid. The rGO thin films were cast usingthe drop-cast technique and dried at room temperature. For their contaminant-freewrinkled form, multilayered graphene structure, high mobility of 2× 10149It is claimed thatto produce nanostructured detectors GO nanodomainsof p-type were carefully inserted into an n-type 3D ZnO nanoarchitecture.These ultraporous nanoheterojunction networks’ features wereinvestigated using physical and chemical approaches, demonstratinghow GO affects the networks’ ability to sense chemicals andlight. By employing UV light activation of the sensing reactions,these nanocomposite materials were also employed to detect many commonVOCs, including ethyl alcohol, propanone, and ethylbenzene, down toambient temperature. Here, 150The two main forms of sensitizing agents, N-doped graphene quantumdots (N-GQDs-NSs) coupled to nanosheets and N-doped carbon nanoparticles(N-CNPs) 9,have b2 nanoparticle (NPs)/GO heterojunction areused. P-type anatase TiO2 NPs made from sol–gelwere used as the channel materials and were implanted in a few stackedGO channels. To determine the ideal ratio of GO and TiO2 NPs within the hybrid channel, extensive microscopic, spectroscopic,and electrical characterizations were carried out. On a SiO2/Si substrate, a back-gated FET sensor was created and put throughtesting while being exposed to various VOCs. At 100 °C, testswith p-TiO2/GO FET sensors at zero gate voltage (VGS =0) demonstrated ethanol selectivity. The lower detection limit ofethanol was enhanced to 500 ppb by utilizing an appropriate gate voltage, significantly enhancing its sensitivityand p-TiO2–GO hybrid for field-assisted sensitivityamplification. Transient behavior in the presence of reducing vaporethanol, on the other hand, served as evidence for the p-type conductanceof the composites of p-TiO2 NPs and p-GO. The pure GO sensor (S9)could not respond at 100 ppm, but the S1–S8 sensors produceda response within the dynamic range of 25–300 ppm. Every sensordemonstrated a stable baseline with predictable sensing behavior with a p-TiObehavior 10.1513O4/rGO composite.It features a low working temperature and a wide detection range.The hydrothermal Sn3O4/rGO composite exhibitsa large specific surface area and a microstructure like a flower.The sensing features of sensors based on pure Sn3O4 and Sn3O4/rGO composites are thoroughlyanalyzed to learn how the heterostructure influences the sensing performanceof HCHO. According to the observed data, the Sn3O4/rGO composite sensor has a significantly higher sensing responseat a lower working temperature than the pure Sn3O4 sensor. 152A susceptible HCHO sensor is suggested and demonstrated using aheterostructure of the Sn2 can cause asthma and other illnesses in people.153 Researchers are concentrating on creating light,affordable wearable electronics with excellent performance, and adaptabilitydue to the recent rapid advancement of gas sensor research.154 Chen and a colleague created a smartphone-enabled,completely integrated wireless system for real-time NO2 monitoring using a flexible ZnS nanoparticle/nitrogen-doped reducedgraphene oxide (ZnS NP/N-rGO) sensor. The device exhibited a responseof 2.2–10 ppm of NO2, a rapid recovery performanceof 724 s, a power consumption of 0.52 W, and an extremely low theoreticallimit of detection (69 ppb) for graphene-based sensors.155As one of the most frequently harmful irritatinggases, NO8156 For use in acetone gas-sensing applications,the Mishra research group reports producing ZnS quantum dots (QDs)via a hot-injection technique , an emerging nanomaterial of the carbon-based materialsfamily, have attracted significant research interest.echnique 12. The g166An acetone sensor was created using a quartz crystalmicrobalance(QCM), which was modified with graphene quantum dots (GQDs) to sensegases. GQDs were produced via citrate pyrolysis, and their characteristicswere determined by high-resolution TEM (HR-TEM). They looked at thesensor’s gas sensitivity to acetone at low concentrations.With a sensitivity of 16.78 Hz/ppm and a minimal detection limit of2.5 ppm, it demonstrated good linearity at less than 240 ppm acetoneconcentrations. The sensor showed high acetone selectivity in a combinationof acetone, butanol, and isopropanol 13. The s9167 The absorption energy of material to certaingas molecules, as well as the associated charge transfer characteristics,are important factors in predicting sensing qualities based on gassensing. Yu et al. performed the first computational analysis to demonstrateMXenes’ potential as a gas sensor or capturer, employing monolayerTi2CO2 for NH3 detection.168 Because metallic Ti2C(OH)2, Ti2CF2, and Ti2C do not have semiconductingproperties, only Ti2CO2 was studied using first-principlesmodeling. Using the most stable structure, the O-functionalized monolayerof Ti2CO2, gas molecules’ possible absorptionpositions were investigated to compute adsorption energy and chargetransfer. Aside from demonstrating gas absorption and charge transferin MXenes, plane-wave-based DFT computation allows for the tailoringof MXene selectivity via controlled oxygen functionalization. Junkaewet al. investigated gas molecule adsorption behavior on four MXenes and their O-terminated surfaceswith electronic charge characteristics.168 When a gas molecule is absorbed, it retains its molecule form oris dissociated on the surface of the MXenes. Theoretical simulationspredicted varied absorption energies of multiple gaseous species onvarious types of MXene surface conditions and their associated chargetransfer for gas-sensing properties. However, just a few laboratoryexperiments on the sensing properties of different MXenes have beenpublished. We report a novel experimental investigation into the gas-sensingproperties of MXenes. Layered transition metal carbides, nitrides,or MXene are composed of more than 60 different types, including Ti2C, V2C, Nb2C, Ti4N3, TiNbC, Ti3CN, and Mo2TiC2.171 By chemically treating precursors of the Mn+1AXn phase, also known as theMAX phase, where M is an early transition metal, A is typically anelement IIIA or IVA; X is C and/or N; and n = 1,2, and 3 MXenes are produced.172 MXenesare a focus of research because of a number of intriguing characteristicsthat promise to lead the way for future sensor development. A fascinatingclass of two-dimensional materials called MXenes has lately attractedinterest for their possible use in gas sensing.173The gas-sensing properties of MXenemay be predicted using thequantum mechanical approach and basic principles based on densityfunctional theory (DFT). Using the Schrödinger equation, DFT-basedfirst-principles examine the electronic structure of materials.2CTx MXene sensor in detecting VOCs. Ona Si/SiO2 substrate, the suggested sensor is a chemiresistivedevicemade by photolithography. The effectiveness of the sensor is examinedin relation to different MXene manufacturing conditions. DifferentVOC concentrations, including ethanol, toluene, benzene, acetone,and methanol, are examined at room temperature. The effectivenessof several MXene-based gas sensors is compared in 174Here, we show the efficiency of a new Mo3C2Tx and WSe2  upon the surfaces of 2D Ti3C2Tx Mxene sheets. The 1D W18O49 NRs were uniformly distributed throughout the surfaces of a 2D Ti3C2Tx sheet to producethe 1D/2D W18O49/Ti3C2Tx hybrids. Comparing the W18O49/Ti3C2Tx composites to the Ti3C2Tx sheets and W18O49 NRs, itwas discovered that they markedly increased the ability to sense acetone.The hybrid sensor demonstrated a robust response to low acetone concentrations,rapid response and recovery times, excellent selectivity, long-termstability, and an extremely low acetone detection limit. The superbsensing performance of the hybrid sensor can be attributed to theuniform dispersion of W18O49 NRs on the surface,the elimination of fluorine-containing groups during the solvothermalprocess, and the beneficial interactions at the interface betweenthe W18O49/Ti3C2Tx sheets and W18O49 NRs.181We providea simple solvothermal method for fabricating W3C2Tx–ZnO nanosheethybrids have been producedfor NO2 recovery and detection under UV light. By usingHF solution to etch the Ti3AlC2 Al layer, Ti3C2Tx nanosheets wereproduced (MAX). ZnO nanosheets’ porous structure is crucialfor the adsorption of NO2 gas. With the aid of UV irradiationduring the recovery process, the Ti3C2Tx–ZnO nanosheet-based gas sensor displayedbetter NO2-detecting skills, including a high sensitivityof 367.63% to 20 ppm of NO2 and a quicker response/recoverytime of 22 s/10 s.182Schottky-barrier-equipped Tix)/graphite (G)nanofilament-based buckypaper sensor was developedby Homaeigohar (183The first oxygenatedamorphous carbon (a-COaeigohar 15. By fo10The development of VOC sensing utilizing CNMsis outlined in thiscomprehensive review. Due to the wide range of uses for VOC environmentalmonitoring, the difficulty of selecting VOC detection is growing everyday. Toxic VOC detection is crucial for protecting the environmentand human health. Due to their unique morphology and features, developingCNMs has been the foundation for sensor technology over the precedingtwo decades. CNMs like graphene, CNTs, and their derivatives, whichhave a large number of adsorption sites, low density, tunable electricalproperties, high carrier mobility, low operating temperatures, longerlives, and ease of recovery, are appropriate sensing materials fora variety of toxic pollutant gases and volatile organic compounds.Numerous researchers have observed an increase in sensitivity thatallows for detecting harmful VOCs at ppb levels. The selectivity ofa CNM-based sensor toward a specific VOC at room temperature has beenshown in numerous papers. According to the literature, metal oxideand nanocarbon hybrids have outstanding sensing capabilities, withnanocarbon serving as the primary component. Composites made of nanocarbonhave shown a strong potential for use in VOC sensing.However,some measure of research should be focused on the synthesisor design of porous or hierarchical structures of carbon-based materialsfor the suitable VOC molecule adsorption with more reaction siteswhich can help with a better understanding of structural-adsorption/absorptionproperty relationships that will garnish sensing mechanisms. Also,by analysis of theoretical calculation, the change of electronic propertiesof host–guest items can be explored for selective gas sensors.


RSC Advances article. These are given below as ref. The authors are publishing this correction to draw the reader’s attention to their closely related papers that should have been cited as ref. 42 and 43 in this F1/F0 were selected to evaluate the effects of the aforementioned reaction conditions on the sensing performance of the developed strategy, where F1 and F0 were the fluorescence intensities of the solutions in the presence and absence of CRP, respectively.42”On page 11963, a citation to ref. 42 should be added to the end of the sentence beginning “The fluorescence intensity…”. Therefore, the sentence should be changed to “The fluorescence intensity and the value of −1 were performed.43”On page 11965–11966, a citation to ref. 43 should be added at the end of the sentence beginning “The detection of CRP…”. Therefore, the sentence should be changed to “The detection of CRP in biological samples by spiking in CRP to human serum, urine and saliva diluted to 10% with buffer solution with the final concentration of 10 ng mLThe authors also regret that there are portions of unattributed text overlap in the Introduction, Results and discussion and Conclusion sections with other papers, including ref. 42 and 43.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.